Please research and comply with all applicable federal, state and local laws and regulations before you undertake a build of any kind. I am very careful to understand what I must do to legally build pistols and rifles before I begin a project. I am not a lawyer and will not give legal advice. If you decide to build something, you accept all legal and regulatory liability. This post is for informational purposes only. Please be careful and please be legal.Do not attempt a build if you lack suufficient experience to do it safely.
Need to start this post with a reminder to be legal and safe.
By this point I had welded my receivers, parkerized them and also prepped some old Israeli Sten magazines. It was time to assemble the Velocity Firearms MAC 9 firearms. Two would be registered as pistols and one as a rifle. They all use the same internals in the lower receivers so I bought complete internal lower parts kits from Velocity Firearms plus complete uppers from them as well. Note, the grip assembly with the mag catch is a separate part. I just bought it from them pre-assembled.
Back grip assembly – includes the Plastic back grip housing, mag catch, mag catch spring and mag catch pin
Optional: This is a Practical Solutions rear 1913 adapter.
Wire retainer for the selector lever and trigger pin
Hammer pin retainer e-clip – it’s still in its bag so I wouldn’t lose it
Takedown pin assembly – tubular body and a hex socket button head screw.
Safety selector
Trigger bar – note bevel goes face up
Sear plate – This is positioned the right way – bevels go down, front slots to cradle the trigger bard are down.
Sear spring
Sear spring holder / spacer – bevel is at the top. This holds the upper in position
Trigger
Trigger pin – note the slot is set further back for the retainer wire
Hammer pin – note slot is out at the end for the retainer e-clip
This is both the hammer and the hammer spring – the spring is oriented properly. The hammer is resting striking face down.
The Practical Solutions 1913 Rear Rail Adapter
I knew I wanted a 1913 Picatiny rear rail for mounting braces or stocks to. I looked at a number and the Practical Solutions model received good reviews. I’ll tell you it is solidly made for sure.
The Practical Solutions unit is well made and easy to install. To create a solid mount that doesn’t flex, I would recommend bedding it with epoxy so there is no “wiggle” room between the rear of the receiver and the adapter.
For the most part I like it because it’s easy to install. You will probably want to bed the adapter in the rear or else it will likely move. I mixed up some epoxy, black dye and 1/32″ glass fibers to make a putty that I then applied between the adapter and the rear of the receiver. Both parts had release agent on them just in case. I did this later because I didn’t realize how easily it could move with a brace or stock acting like a lever arm.
There is a lot of adjustment room to accomodate a wide variety of builds. This is a pro and a con.
Also, the bushing will push the spacer up just a bit so you might want to grind/sand/cut a radius so the spacer can seat properly. Alternatively, just bend the spacer. I just bent the spacer until the upper would fit.
Either notch your spacer to avoid that bushing or bend the spacer to reduce the height enough.Ok, I found out about this after I fully assembled the VMACs – the rear of the VMAC and the Practrical Solutions adapters do not sit perfectly flat against one another so the adapter could flex left and right. Honestly, not a big deal. I just mixed up some black glass fiber reinforced epoxy and created a filler/spacer between the adapter and the rear of the weapon. Problem solved. By the way, my intent was never to “glue” them. I applied release agent on both surfaces so they can be removed. If you don’t have a release agent like Mann Ease Release 200, use PAM cooking spray or a bit of shoe wax to the surfaces before you apply the epoxy. If you want to bond them directly, go right ahead.
Let’s step through the assembly
Install the plastic grip assembly taking care the mag catch’s half circle end sits outside of the mag well.
Take the sear plate, tip the rear up and lower the front forks down so they slide under the bullet guide’s arms. The beveled front and rear rails are face down. Another way of thinking of the orientation is that the trigger bar slides under the front of the forks and sits in the machined opening. Make sure the sear plate can slide all the way forward to the center support and all the way to the rear. If there are any welds in the way, grind them so everything slides smoothly.
At this point, I start lubricating as I go. If it slides, grease it. If it rotates, oil it. I use SuperLube grease applied with an acid brush to all surfaces that need greasing. Oiling was done with SuperLube oil. I like the two as they are synthetic and don’t get gummy plus they have PTFE (the generic acronym for Teflon) added to improve lubricity. The coarse parkerized surfaces will want to slow everything down while they wear in.
Slide the sear plate forward, install the spacer to the rear with the beveled face up. Try test installing an upper at this point. You may need to squish the spacer a tad in a vice to allow the upper to seat easily.
Slide the sear plate spring onto the sear and move the sear to the rear so it is all inside the sear spring holder / spacer.
Insert the trigger bar with the beveled face up. I used needle nose pliers to do this and slid it under the front of the sear plate.
Move the whole trigger bar and sear plate rearward so you can drop the trigger into the hole in the receiver and also such that the trigger is in front of the trigger bar.
Insert the trigger pin from left to right. This requires a little bit of manipulation to get the pin through both sides.
Install the hammer spring it it hasn’t been already. It should be oriented the way you see above.
Install the hammer in the rear. It sits like an AR hammer with the flat face forward. The spring legs rest between the sear plate’s legs.
Install the hammer pin
Put a daub of grease on the receiver around the hammer pin. This is an old trick and will hold the e-clip in position while you slide it on. I’d recommend using something non-marring to push the e-clip on and you’ll feel the cip snap into position. Another trick is to lower the pin such that the slot is even with the receiver so you don’t have to try and get the clip at the right height while fighting everything else.
Install the retaining wire by sliding the forward portion under the front reinforcement. The hooked portion sits in the groove on the right “ear” of the bullet guide. I’ll show photos below.
Technically, you are supposed to lift the retaining wire up and insert the selector under the wire. This is what adds the tension to lock the selector and trigger pins in place. Uhm .. there was no way I could do that. If you can get it together/ go for it. I was getting pissed off and needed to think of a different approach. So, if you were able to lift the wire up and install the safety selector lever then you are done with the lower. Speaking for myself, I had to add the following:
For the life of me, I could not get the selector lever in due to an elevated area on the inside and I couldn’t get the wire any higher. Instead, I backed off the trigger pin and inserted the selector because the tension was gone. The issue then became how to get the trigger pin in. What I did was to align the pin on the hole and used a grooved screwdriver (spanner bit) to forcefully push the pin and retaining wire down facing the hole while pushing from the other side so the pin would pop into the hole. That worked. One reason it worked was that I could see what I was doing and how to move things whereas with the selector lever and wire, I couldn’t see what was going on.
Note, you will need to help the sear plate and hammer to go into the cocked position before you install the upper.
I did a quick function test while controlling the hammer so it wouldn’t smack into things. Pulling the hammer back, the sear plate would grab it. Pulling the trigger back, the sear plate would release the hammer – again, I caught it vs. letting it fly free. I squeeze the trigger back, moved the hammer back, let go of the hammer while the trigger was squeezed and the sear plate grabbed it. I pulled the trigger and the hammer “fired”. I then made sure the safety worked. Everything was good.
Now For Photos
I find the sear plate fascinating. Yeah, I’m wierd. It’s almost like Ingram was designing a miniature bullpup. He had to create a trigger linkage that could bridge the distance from the trigger located in front of the mag well / grip to the rear where the hammer was. He came up with this design. Folks, this is pretty damned ingenious. First off, I have it flipped upside dowhn and the left would be to the front of the weapon and the top right would be facing the rear. A sear is what holds the bolt, hammer or striker back until enough pressure is applied that said device is released. In the case of the MAC, the sear plate is a forged piece of steel and let’s cover some of the unique design elements (remember it is inverted for this picture): 1) The hammer bar sits in the notches in the arms of the plate. 2) The plate has bevelled skates/runners/thingies that are bevelled to accomodate the radius of of the receiver bend and also reduce the surface area of the plate so there is less friction against the receiver plus they will probably push a fair amount of debris out of the way. 3) the plate is split into a fork to pass the left and right of the mag well. 4) the rear triangle is a lightening cut 5) the sear spring sits on/around the protruding “tail” at the rear of the plate.Unless you like the fun of “where did that part go?” I’d recommend putting the parts in a magnetic parts tray.The grip is installed on the steel mag well by keeping the bottom of the mag catch (the half moon shape) on the outside of the mag well so just the square “shelf” of the catch is inside. That half moon sits on the bopttom of the slot in this photo – which would be the top of the slot when the VMAC is upright. The grip is held on by one screw. If that screw doesn’t want to start or you do get it together and then can’t insert the mag, odds are that whole mag catch is accidentally inside the grip.I did it the wrong way – see how the whole mag catch “arm” is in the mag well? I could install the grip but I could not insert mags. This photo is out of sequence so you can see the mag catch.See how the squared off “shelf” of the mag catch is the only thing sticking into the mag well? That’s what we want – that is correct. I did not need to do any alterations for surplus or polymer mags. Both mag types lock up nice front to back but are loose left to right.I welded the heck out of the sides. After looking at the plastic grips a tad bit more closely, I could have done a small weld on that rear tab and it would have cleared the grip. Look at the photo above – the top inside edge of the grip is hollow and would have cleared it. Live and learn I guess. That mag well will not budge given the weld I did on the sides and front corners but I would have done that rear tab had I known.The intent of the photo is to show you the orientation of the trigger bar, sear plate, sear spring and the spring holder / spacer.
I don’t have a photo but make sure the sear place and trigger bar can slide unobstructed. If there are welds or anything in the way, grind them out, then blow out the receiver before you coat everything in grease.
Insert the sear plate with the rear tipped up at an angle. This will give you enough room to slide the front legs under the bullet guide. Yeah, I grease everything that slides.Slide the sear platforward and insert the spacer. If your spacer has a bevel, it goes face up as shown in the photo. Since I installed the Practical Solutions adapter already you can see it is riding high. The solution is to compress/crush/bend the spacer and trial fit the top. Bend a bit and test over and over until you can full seat the upper.Slide the sear spring onto the sear plate and side it backwards. I use needlenose pliers to lower the trigger bar in place with the beveled edge to the front and face up.Push the trigger bar, sear plate and what have you rearwards and insert the trigger forward of the trigger bar as shown.To be clear, the top pin is the trigger pin. You can tell because it’s groove is further away from the end and that’s where the retaining wire will sit. The lower pin is for the hammer. The groove is right near the end because the retaining e-clip actually sits outside of the receiver. When looking down at the open receiver with it facing forward, the pins are inserted from the left to the right. In other words, the heads will be on the side opposite the ejection port.Insert the trigger pin.Compared to an AR or AK, the hammer assembly goes in without a fight because the hammer can rest without spring tension during installation. The hammer pin can easily be pushed through.Put a daub of grease on the pin and surrounding area. This will help hold the e-clip and keep it from flying into another dimension only to be found by the next person who owns your shop. I like to lower the pin so the groove and e-clip line up and then I use a non-marring surface to push the e-clip into position. You will feel it click into position.Here is the pre-bent retaining wire. It was designed by someone who literally wanted to remove all the joy that is left in the world.So the hook on the retaining wire rests on the bullet guide. You install it by sliding the far end first. There’s no tension yet. That comes when you install the safety selector. That’s also when the swearing starts. You can’t see or get ahold of that wire thanks to that tab that is there, in part, to make this a semi-auto receiver so I wasn’t about to cut it off or bend it.You are supposed to lift the front of the spring up so this opening is more clear and slide the selector lever in.Okay, so imagine you are sliding this into the hole. The spring hits that first shoulder to the right of the flat area in the shaft. I could not get the damn wire, which is now under tension, to clear that shoulder and go into the groove. In hindsight, bevelling that surface would probably have solved my problem. At the time, I was pretty pissed off after trying too convince it to go in, pulling up on the wire, etc.My workaround was to back off the trigger pin and release the tension from the wire. I then installed the safety selector switch. I then used a spanner screw driver bit to push the trigger into the hole. Pushing it down also tensioned the wire so it took some force. The trick was controlling it.The receiver is sitting with teh bottom cradled in my big woodworking vise. Note the safety selector is installed with the retaining wire in its groove. The trigger pin is lined up with the hole. What I did was push down with the spanner screw driver while pushing the pin to the right with my left hand. I had to use the vise because it took two hands but it worked. I did those for all three lowers and it works just fine.Well, the retaining spring is installed.You do need to manuall bring the hammer back and catch it because there is no upper to stop forward travel or bring it back. You absolutely can install an upper with the hammer all the way down and wonder why it’s not cocking. Look in the trigger well – if you see the hammer laying flat it’s because you forgot to cock it before installing the upper. When you see tips like that, it means I did it 🙂
Be sure to do the function testing outlined above. All weapons should be cautiously test fired to ensure safety.
Summary
I was actually impressed by the design other than my extreme dislike for the retaining wire. The trigger is better than I expected. Not great but not horrible either.
In the next post, I’ll take about the first upper and how I configured the firearm.
I hope this helps you out.
Note, I have to buy all of my parts – nothing here was paid for by sponsors, etc. I do make a small amount if you click on an ad and buy something but that is it. You’re getting my real opinion on stuff.
If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at in**@ro*********.com. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.
Back in 2017, I planned to build a Sten Mk. V and actually am planning to move forward with it now that I have built some VMAC9s that use Sten magazines. Well, as part of the VMAC builds, I bought some of the new MPA Polymer Sten mags and also decided to refinish some incredibly flithy Israeli modified Sten mags and loaders just caked in ancient cosmoline.
The Magazines
The Israelis had many different weapons in use following WWII including British Sten guns. Somewhere along the way they realized they could improve reliability by limiting the magazinees to 20 rounds via long skirted followers, adding brass wire on the sides to better stabilize the followers and soldering the bullet count peepholes closed.
At some point in the late 1950s, they phased out the Stens put thousands of these modified Sten magazines into long term storage where the preservative dried out, some rusting started and they became just genuinely filthy.
Closer to modern day, a US importer bought them plus we had Sten kits coming from all kinds of places. I bought two ten packs of filthy Sten mags from Centerfire Systems for a song, I have had the kits and these mags sitting in a tub.
Cleaning Them Up
The surplus steel mags are way too filthy to be reliable out of the box plus they look ancient. So, I opened up one the bags of 10 plus an odd box of six and oh man, did they need cleaning. I fired up my Vevor Ultrasonic cleaner that is filled with Simple Green HD, heated it up and then put the mags in there. My fluid was old to begin with but chunks of who knows what were floating up the surface as I ran 3-4 15 minute cycles trying to clean the things up. I’d do one side a couple of times, flip the mags so the other side was then face up and do it again.
They were in tough shape. The mags in a box were on better shape than the ones in the plastic bag. One of the mags looked like it has been put away wet or something. The inside was very, very rusted.The mag loaders were caked with old cosmoline.The solution was about 150 degrees. This is after the first 15 minute cycke.I took some of the magazines and just oiled them after cleaning vs refinishing. That’s an option for you if you want.
Manganese Parkerizing the Surplus Sten Mags
The mags were disassembled and I used a sanding mop to quickly score the surface of the mags. Abrasive blasting would have given a more consistent surface and better results. I hosed them down with brake cleaner, let them dry and put bodies, followers and base plates in my parkerization solution – click here for more info on how to make your own black manganese park solution and process to follow.
Everything was lubed with 10w30. I like to scrub with steel wool to remove any loose surface phosphate. Note, I did not park the springs or locking plates.They came out pretty good – better than I had thought they would.Here’s one of the in process VMAC9 pistols with one of the mags installed. Most of my mags had “character” marks including dings and some light rust. All except for one were salvageable.
Summary
With a VMAC9, you can either use the MPA polymer Sten mags or original steel Sten mags. I actually plan to test both. I like the looks and history of the 20 round Israeli Sten magazines. The steel Sten mags are out there and are affordable if you don’t mind doing a little cleaning.
I hope this helps you out.
Note, I have to buy all of my parts – nothing here was paid for by sponsors, etc. I do make a small amount if you click on an ad and buy something but that is it. You’re getting my real opinion on stuff.
If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at in**@ro*********.com. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.
Velocity Arms finishes their VMAC9 uppers using a “manganese phosphate finished IAW 5.3.1.2 of Mil-STD-171” which is a fancy way of saying maganese park, heavy coating, class 2, oil coated. Of course the military gets into a lot of details further specifying it in MIL-DTL-16232. At any rate, Velocity Arms’ uppers are a nice rich dark black manganese park finish and I had a pretty good idea of how to duplicate it based on past experience.
I’m not going to get into all of the chemistry details – if you want that, click here for Wikipedia. I am going to point out, there are two types of park – zinc and maganese. Zinc is more of a grey or grey/green. Manganese is dark grey to black. What I have found purely based on experience is that an abrasive blasted clean steel surface will turn black in a fresh park solution and it approaching boiling and left in for 30-45 minutes.
Surface Prep is Critical
One thing I have found is that you just can’t take steel and drop it in park solution. You may get little to no reaction plus if there is oil or grease on the steel, you may contaminate your park solution so bad you have to discard it.
What I do is put on nitrile gloves, clean the part with brake cleabner thoroughly. If it’s bad, use an ultrasonic cleaner with a good cleaning solution. When the part is dry, then abrasive blast it. I use Black Diamond blast media from my local Tractor Supply (TSC) store. Never use sand – the dust from that is incredibly bad – really, really bad – for your lungs because it goes in and doesn’t come out. With Black Diamond, it does a wear out so I watch my parts and when the blasting starts taking too long, I replace it.
Clean everything and blast the part. The steel should all have a frosted look or it probably didn’t get blasted enough. If you get done with parking and an area didn’t take, hose it down, dry it, blast the affected area and a bit of the surrounding area and try again.
When I am done blasting, I clean it again with brake cleaner, let it dry and it’s time to go into the Manganese park solution.
I usually brew my solution and let it start heating up and aging while I get my parts ready.
A Manganese Home Park Formula That Really Works
I have used this formula for years. One ingredient though, Prep & Etch , is getting hard to find so you will either need to find an alternate or make your own mix.
This recipe generates about two gallons of mix so figure out your ratios if you want to make more:
2 gallons of distilled water (it gives more consistent results because impurities have been removed – sold at supermarkets and drug stores).
2 “biscuits” of clean plain 0000 steel wool (thinner steel wool dissolves faster hence the use of 0000 grade) – Click here for them on Amazon or here for eBay
1 cup of Klean Strip brand Phosphoric Prep & Etch (or other phosphoric acid etching solution around 35-45% concentrate per the Prep & Etch MSDS sheet. Dilute the acid if higher. For example, if 100% pure then go 60 water:40 acid to make the diluted acid solution that you add to the mix. This is not the ratio in the park solution itself – you can always experiment with the ratio that works for you). I can’t find Prep & Etch at any local stores but my local Ace Hardware is carrying something similar called “Ospho” and the SDS sheet identifies it as 45% phosphoric acid and it ought to work but haven’t tried it yet. I had two gallons of Prep & Etch and that amount has lasted me a number of years because I don’t do a lot of parking but you get the idea. Click here for Phosphoric Acid on Amazon or here for eBay.
6 very rounded tablespoons of manganese dioxide (available at pottery supply stores, Amazon or eBay). Do NOT mess with batteries. You may read about guys who open up batteries to get the manganese – don’t do it. Just buy the actual manganese in bulk. It’s cheap and you know what you are getting.
Heat Source & Vessel
Some years ago, I bought a Camp Chef Explorer two burner stove off Amazon and I really like it. It’s sturdy and can run off any of the common propane tanks. Also, there are many different sizes of stoves out there but I wanted a beefy two burner to be able to also heat my stainless tank when I park long parts.
I use 20 pound tanks because they are easy for me to move. I just swap cylinders when they pass their inspection date but otherwise get them refilled at my local Ace Hardware. Surprisingly, they tend to have the best prices in the area for propane.
In terms of what I use to hold the parts, the receivers were short so I just used a 12 quart stainless pot I have for that purpose. Note, do not use cookware for this. I’m not joking. I can just imagine some guy thinking “Oh – I’ll just use a pot from the kitchen.” This stuff leaves residues that you should never eat. I have a couple places on the bottom of my pot where I can’t scrape some kind of crust off. My best guess is that the alloy wasn’t consistent but regardlss, do not use pots or other containers from the kitchen. Buy and use dedicated pots, tongs, stainless wire, etc.
By the way, good long stiff BBQ tons are definitely worth it. I have one with plastic jaws and another that is completely stainless. While I was worried at first about scratching the parts, I really haven’t had a problem with that. Amazon has tons of affordable tongs with decent reviews.
In cases where I can’t run a wire through the small parts, I use the strainer/steamer section of my boiler pot or a small kitchen stainless strainer in my big tank if I am using that.
Add acid to water in a stainless pan/pot and heat to 190F – don’t boil and waste it – if it does boil or simmer, it’s not the end of the world and a lid can help reduce evaporative loss. I use a baking thermometer clipped to the side of the pan or my Fluke infrared thermometer.
Spray each wool biscuit with brake cleaner to remove oils and allow each time to dry.
As the solution warms shred the steel wool into the liquid and add the manganese dioxide. When I did these Vmac9 receivers, I found all I had to do was unwind the steel wool rolls, place them in the solution and that was fine.
Let the mix simmer and dissolve the steel wool before adding parts. This is key. The solution needs to dissolve the steel to get the process started. I usually, get this started and then get my parts ready. Stir periodically to help things mix.
Here, the solution is brewing while I get the receivers ready to go into it. That is a 12 quart stainless pot sitting over one burner of my Camp Chef stove.
I always blast my parts before I parkerize them. I have used sanding mops and other approaches to expose the metal but just find blasting the best for a consistently colored surface. Blasting removes the oxides and exposes the bare steel. I always do that.
Make sure your parts are very, very clean and degreased — only handle with rubber gloves after they are cleaned or oils from your skin can mess things up.
Before you put your parts in, stir the solution to keep the manganese dioxide suspended. I do not stir once the parts are in the pot or tank.
You can suspend your parts in the liquid with stainless wire. Leave them until the fizzing stops or about 30-45 minutes. The time varies depending on many factors including the solution itself and the heat.
All three receivers were in there and I let them simmer for about 45 minutes.Here they are fresh from the pot. I use kitchen tons to pull them out because they are hot. I also am wearing nitrile gloves and eye protection. Again, do this outdoors. You don’t want this condensing on exposed steel in your shop and case rusting.
Rinse the parts with boiling water thoroughly to remove the acid. I have never found the need to do more than thoroughly hose down the parts. I literally use a garden hose.
Spray parts with WD40 to get the water away from the steel.
Here are all three receivers soaked in WD-40 after being hosed down. I then rubbed them down with 10w30 engine oil.
Wipe down with oil or apply whatever secondary finish you want – don’t do both 🙂 If you are going to apply a finish on top of the parkerized surface, use acetone or brake cleaner to remove any oils and then follow the vendor’s instructions.
Now, you have another option also – After the oil rub, I heated them up to about 125-150F, let them sit for a bit and then rubbed in Sno-Seal boot wax to just really seal things up but also keep the parkerizied look.
Here’s a view of them together:
Herre they are ready for assembly. The park is nice and consistent. I did need to redo one of them. There was a spot I didn’t blast enough so the park didn’t take well. I blasted that area and a bit more, cleaned it up and then redid it. I did this right after hosing the part down – that’s when I noticed it.
Summary
You can definitely do a manganese park at home and make your own recipe that is just as dark as what Velocity does. The receipe and process above are affordable, easy and generate great results as evidenced above.
I hope this helps you out.
Note, I have to buy all of my parts – nothing here was paid for by sponsors, etc. I do make a small amount if you click on an ad and buy something but that is it. You’re getting my real opinion on stuff.
If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at in**@ro*********.com. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.
Please research and comply with all applicable federal, state and local laws and regulations before you undertake a build of any kind. I am very careful to understand what I must do to legally build pistols and rifles before I begin a project. I am not a lawyer and will not give legal advice. If you decide to build something, you accept all legal and regulatory liability. This post is for informational purposes only. Please be careful and please be legal.
Need to start this post with a reminder to be legal and safe.
When I was a kid in the 70s and 80s, the Ingram Mac-10 and 11 submachine guns (SMGs) were in tons of TV shows and movies. You could see these iconic blocky little SMGs everywhere with their equally famous two stage suppressors. So, they must have been amazing – right? Well, the truth is their reliability wasn’t that great, they had an insanely high cyclic rate that could dump a 30-32 round mag in about 1.5 seconds and a very short barrel. So, iconic was a big “yes” but effective … well, not so much.
This is the first post of a series wherein your’s truly felt like building something, had a fit of nostalgia and decided to do a MAC-11 in 9mm. This was partly triggered by seeing a lot of really cool printed 3D pistol designs that utilized a MAC-11 upper. I don’t have a 3D printer because I don’t have time to learn one and my wife also told me in no uncertain terms that I was not to buy one … although she may forget this one day 🙂 If you are into 3D printing, search for “MacDaddy 3D Print” and you’ll find the many variations of it.
So, on a whim, I googled Mac-11 kits one day and found receiver options that could be bent from a flat or welded together. I didn’t feel like either buying a flat bending jig or making one but I can weld somewhat. If you know the slam “he’s a grinder, not a welder” – that’s me. I’m marginal with a welder but let me assure you, I know how to sand. Thousands of grips and handguards later, I absolutely know how to sand.
Now you have two options on the side plates – when you buy the kit, Velocity gives you a complete set of prints so you can make your own or you can buy the plates already cut and ready to go from 2D3Dlaser.com. I thought about building them but didn’t really feel like it and the 2D3D plates had really good reviews so I went with them — and I’ll tell you right now they are nicely done.
This photo has all of the parts you will weld together. Surprisingly, they are all 14 gauge cold roll steel (so were the originals). Top left is the mag well/grip assembly and to the right of it is trigger guard. The odd flare that sticks up at the back is the bullet guide. Under them is the center section. Under that to the left is the rear sight plate, and to the right of that is the front takedown pin reinforcement. It actually should be turned to the right so the holes you see on the top “U” line up with the holes in the side plates. Under those two is the left side plate – you can tell because it goes straight across the top. Finally, below that is the right plate. I paid 2D3D to print SAFE and FIRE and the selector plus you can see the small depression that aligns with the bolt carrier face and ejection port of the upper. See all of the cutouts on the center section and tabs on the other parts? Those help you align the parts.
You need a welder
First off, you need a welder that can handle 14 gauge sheet metal. I like using a MIG welder with a 75 % Argon / 25% CO2 gas – this is often referred to as “C25 gas” due to the ratio. This can generate very clean welds. The cheap flux core MIGs will work but they have a chemical known as “flux” inside the hollow steel tube that is melting to shield the weld from the atmosphere and it splatters everywhere requiring more clean up.
The best welder you can use is a TIG – those things can generate beautiful welds and there are cost effective entry level welders but they always must have a shielding gas – usually of 100% argon. I spent a bunch of money on a really nice TIG and couldn’t use it because my hands shake too much – I have what is called a “hereditary tremor” and fine motor work like dabbing a welding rod into a weld pool just isn’t something I can do no matter how well my arms and hands are supported.
I got by with a cheap Harbor Freight welder for years. When I decided to get a better welder with more depth and a longer duty cycle, the difference was night and day. Most of the time I am fabricating/repairing pieces of steel ranging from 1/8: to 3/8″ thick. I also have found that cheap wire is messier than good wire. I’m running Lincoln 0.035″ diameter ER70S6 wire.This is two parts of the test coupons I bought from Amazon. They give you a bunch of test areas with the pieces they send you and it’s worth it – unless you just happen to have scrap 14 gauge cold roll steel laying around.Welding is not the same as gluing. Technically you are doing fusion welding. The filler metal being introduced is molten and fuses the two metal pieces together., You don’t want the weld to be superficial or so hot that the steel is running/flowing away either. I did this test coupon and tried as hard as I could to separate it or bend it and I couldn’t. If it had pulled apart or broken easily then I would have known I needed to adjust my welder – probably by dialing up the heat. My point is that the weld fuses the pieces together and then you can sand the bead down if you want to. My beads always look like crap so I always sand them down with a grinder or flap sander.The Millermatic 211 MIG welder can automate some of the settings. In the top middle, it is set to C25 gas. Note it can use C100 and flux core plus has an aluminum setting. On the bottom right, I can manually set the wire feed speed or just specify the diameter of 0.035″, which I did here. The Autoset Thickness dial on the left lets me control the volts. If you are wondering why volts and not amps are being set, it is because the Millermatic uses an inverter and you adjust the voltage instead for a better arc and uses less power. On the test coupons, I found I got the level of penetration I wanted with the dial closer to 6. The 14 gauge recommended setting is from 5-6.
I really like Miller welders and Lincolns are good too but you are going to pony up money for either one. If you plan on using your welder a lot buy the best you can afford. Thickness, duty cycle and the quality of the weld all depend on the quality of the electronics in the welders.
If you are new to welding get either a 120 or 240 volt MIG welder. MIGs just make life easier as the welder feeds the steel wire into the weld and the wire is the electrode that is conducting electricity and melting. It’s surprisingly straight forward for a person new to welding. You can start with flux but gas is better – some welders can do either and that would give you some flexibility.
Now one thing that also is critical with a welder is a helmet. The arc from a MIG can really mess up your eyes as it generates quite a bit of UV radiation. I like auto-darkening masks because I can see good and when the arc triggers the lens jumps to the specified level of shielding. I’m currently using an Antra and really like it. A good mask will trigger fast, go darker and usually have both solar and battery backup power. I also keep it in a helmet back to protect it.
By the way, avoid cheap no-name auto darkening helmets. If they are slow to trip and go dark then more damage happens to your eyes. Some guys like permanently shaded helmets so they don’t have to worry about batteries, cumulative effects, etc. They lift their helmet up, position everything and then do a head bob motion so the visor comes down and away they weld. The choice is yours.
This is my third or fourth welding helmet over the years. It is an Antra True Color Wide Shade helmet. Also on table, you can see one of my welding glove sets. The MIG gun is resting in a magnetic clamp holder and it’s all sitting on my Harbor Freight small welding table. I have a big Dewalt welding table for larger jobs.
Cover yourself up
Last welding comment – cover up. There are two reasons for this. First, the UV radiation will give you a really nasty radiation burn that is deeper than a sunburn. I wear a long sleeve shirt and pants. It’s not happened to me (honestly) but I’ve talked to guys who were wearing shorts and welding crouched down and they burned the inside of their thighs so walking absolutely sucked for them – two guys and they both said “I didn’t think I was going to weld long enough for it to matter. It wasn’t me because I own mistakes so others can learn – I sure learned from them.
The second reason to cover up is that welding generates “spatter” – little droplets of steel that can get blown off and cause small burns. Shit happens. I’ve been burned through just about everything at one time or another and being covered up just reduces the odds. Guys who weld a lot will wear a leather apron, jeans and safety boots.
Always wear welding gloves for a boat load of reasons – spatter, protection and insulation from heat as you weld. Gloves also reduce the odds of burning the crap out of yourself when you accidentally grab/catch something hot.
You’ll need a collection of clamps
In addition to the welder, you are going to need clamps. How many kind of depends on how you clamp everything together. BTW, plastic clamps can hold stuff but don’t weld anywhere near them or they will melt. There are C-clamp assortments on Amazon.
I took a quick photo of a box I had clamps sitting in for this project. I have 3-4x this many clamps.
You’ll see I have a variety of 1″, 1.5″, 2″, and 3″ clamps plus one 6″ clamp for the handle. How many you need of each depends on how you decide to do your welding. A couple of pieces of scrap metal will also help with your clamping so you can apply even pressure.
In general, you need to securely clamp what you are welding so stuff doesn’t move. The better job of clamping you do, the less rework you are going to experience from things shifting.
Various sizes of magnetic welding clamps come in handy too. I have all different sizes ranging from pretty small – maybe 1-2″ and then up to 4-5″. The come in handy for holding work in place and keeping it from sliding around. There are a lot of options on Amazon.
The actual clamping and welding
I planned to do three receivers – two pistols and one rifle. So, I tried welding three different ways:
First Receiver: I clamped the grip, trigger guard and center section together, welded them and then used a right angle piece of aluminum to clamp the right side plate into position welded that, did the same for the right side plate and then the center reinforcement plate. Then I welded in the rear sight.
I tried to do the trigger guard, grip and center section all at once. A 6″ clamp and two pieces of 1/8″ thick scrap metal were used to evenly clamp the grip to the center support. A 2″ clamp was used to secure the trigger guard to the grip.When you weld sheet metal, do not just pour on the heat. If the sheet metal gets too hot it will sag/melt. It will also likely warp. To avoid this, tack weld the pieces together first. Tack welds are small spot welds. When everything is tacked, go back and weld small sections at a time rotating a round to keep the heat and warping low. I did not do the above all at once. Note you do not weld the back of t he grip or you will block the black plastic grip assembly.I inserted a piece of right angle aluminum in the front and clamped down the one side. You do not heed the right angle – the center reinforcement is plenty but I did not know this yet.I welded the slide plates on – first with tack welds and then increasing the welds. A 21/64ths” drill bit shank holding the center reinforcement in place prior to doing a spot weld in the visible hole. I did not weld the top rear of the receiver to allow for tuning. The red objects are magnetic clamps.I did a weld in the middle and then on the sides just to make sure things don’t move later.The welds look like crap you say? Yeah – but if I can pull this off so can you. I shoot single welds and aim for good penetration due to my tremor. Then I grind/sand to clean up.I use a Ryobi 18volt 4.5″ grinder with a 7/8″ arbor and use Neiko 40 grit flap sanding discs. I like the Neikos because they are thicker than cheaper models and the grit seems to last really well. I did not wear out one disc doing all three receivers.So the Neiko flap sander did the bulk of the crude work. I did use a 120 grit disc to quickly clean up the three receivers before I abrasive blasted and parkerized them.40 grit sand paper in a grinder can take off material fast – even steel. I’d recommend having the work at a comfortable height secured in a vise. The wood inserts you see are something I slapped together for my big 6″ outdoor vise to hold the receivers and not tear them up. The vise has hardened jaws and would chew up the mild steel receivers if they were holding them directly. At any rate, be conscious of the angle of your grinder and focus on knocking the beads down. Take care not to let the grinder remove/thin out the base sheet metal.Done for now. I later levelled most of it our using a 120 grit flap sanding disc before abrasive blasting. The whole point of this is to fusion weld the pieces together and remove the extra beads. I then used a sanding mop to round over the right angles on the sides. By the way, these are for my own use. I’m not selling them so they just have to be good enough to me.
Lessons learned: 1) Don’t need the aluminum right angle to orient the side plates. The rear bend in the center section and the takedown pin reinforcement can hold it just fine. This dawned on me as I was sliding the reinforcement section into position. 2) a piece of sheet metal on top of the side plates would probably be a better way to secure them. 3) Also, I really needed to connect the ground straight to the receiver to get a better connection.
Second Receiver: I clamped the trigger guard, grip and center support together and welded them. Then I inserted the front reinforcement and clamped the side plates at the front, back, middle and welded. I then did the rear sight plate.
So the second one started in a very similar manner.But this time, I took more photos and with better lighting.Tack welds are in.I was clipping right along feeling good about stuff but broke a cardinal rule – I didn’t check the clamps and the workpieces. The magwell/grip is true but trigger guard assembly cocked sideways somehow and was no longer perpendicular with the center section. Well crap! So, I used a Dremel with a cutting wheel to cut off the trigger guard and welded it square. I used pliers to true the bullet guide so it was perpendicular the way it should be with the receiver. The slot you see is where one of the side plate tabs went into the recess on the center section. I welded them closed and ground them flat later.I used plenty of clamps to make sure nothing else moved and then did the spot welds. Note the ground is right on the receiver. The magnets are keeping the assembly from moving. You can see the spot welds. I would then move around welding a bit at a time to avoid warping or sagging. There is a 21/64ths transfer punch aligning the center takedown pin reinforcement.To be clear, I welded the center section after the side plates were welded in. The I pulled out the alignment pin – in this case a 21/64″ transfer punch.Clamped getting ready for the flap sander. Note, I would need to move the receiver around about 4 times to get all of the material off. It was never in one go.A good chunk of the weld bead on that side was gone at this point.Two roughed in receivers. No finish sanding yet.
Lessons learned: 1) Check your clamps and work to make sure nothing shifted. I could have kicked myself – that was such a basic mistake. 2) the center section may not be true – use some scraps of metal to pull the center section and side plates together. 3) More clamps are better than fewer clamps. 4) Maybe I should try welding the trigger guard by itself first – and I did that with the next one.
Third Receiver: Clamped the trigger guard to the center section and welded it. Positioned the magwell/grip, clamped and welded it. I then positioned the front reinforcement piece, clamped the side plates and welded.
Through the use of magnetic clamps, I made sure the trigger guard was all of the way forward, true and tacked it in place. Then I moved on to the magwell/grip.So then I clamped the magwell in place, did the tack welds and then welded it all in.I’m holding it together but see how the plates are held vertically by the bullet guide and the front reinforcement? The trick is to properly locate everything and then clamp it.So I’m welding along the seam. What you can’t see is that I let it get too hot and I pushed through the other side in a few placesI welded in the ceterpiece. You can see the 21/64″ hole center punch aligning everything.Finishing up the weld on the seam.Welded in the rear sight plate. I welded the bottom edge closed so I could clean it up later – I did this on all three.I inspected the bottom of all three also. I added beads on all three receivers so I could get good penetration, fill in the slots where the tabs went and have a right angle I could then sand over. Again, note no weld on the rear of the mag well.Time to sand it down and clean it up.Again, we sand down all of the beads and clean things up.And number three was done awaiting finish sanding and parkerizing… or so I thought.,
Testing & cleaning up
Okay, you need to make sure thee sear plate can slide from the back all the way to the forward towards the center support. The reason being is that if you have any welds interfering with it’s ability to slide forward or the trigger bar, your action is going to be messed up. If you have welds in the way, you are going to need to grind them down.
The sear plate must be able to smoothly slide forward and backward and not have any welds in the way.
This is one of those things where avoiding them up front my not going crazy with the heat would have been a good idea on my part. My first two were great. My third receiver had issues and I even know when I did it.
So far, things were going smooth. The VMAC9 lowers were welded together awaiting next steps. In the next post, I will cover how to given them a nice black manganese parkerized finish.
I hope this helps you out.
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