As I mentioned in the first post, a fit of nostalgia over the MACs and then seeing the 3D printed firearms coming out using MAC uppers started me digging. What really cemented the deal is that you can build a VMAC9 very affordably. I’d argue it’s one of the best deals out there and at the end of the day, you have a modular firearm you can change over time as your needs change.
There are a number of companies that make complete uppers and I am only going to list the ones I heard good things about. Just remember that any person or business can produce a defect. I look for general trends, comments about customer service and how much money is being spent. The reason for this is that under a certain price level, I will gamble. Conversely, once somethings is over a certain level, I will not.
So, here’s the list if you are looking for MAC-type uppers and I’d recommend you do some research to here what folks are currently saying about a given company:
Being new to building a MAC, I decided to one stop shop and buy the lower and upper parts kits from Velocity Firearms. I went with side cocking uppers because I wanted a Picatinny rail on top to mount optics. I bought their 5.5″, 11.25″ and 16.7″ complete uppers – they had their barrels installed and came with complete bolt and spring assemblies.
Up to this point, I had three assembled lower receivers. Once married with their respective uppers, I created two pistols and one rifle subject to the applicable regulations of the ATF and laws of Michigan. The two pistols had to be registered as such. Note, I am not a lawyer and this is not legal advice. I will tell you one thing – know what laws and regulations apply to whatever you build.
This is the 5.5″ pistol upper on a lower during test fitting. The magazine is a refinished Israeli 20 round Sten unit. You can get a barrel with either just the original 3/4″x10 rear threads or with the 1/2″x28 front threads also.This is the 11″.25″ upper. They used an adapter on the barrel’s 3/4×10 threads to mount an AR handguard. What you see there is a free-floated handgurd where a ring is turned backwards to extend and lock the handguard in place and a set screw is tightened to secure it.This is the 16.7″ upper and the cylindrical handguard you see mounts directly on the barrel’s 3/14×10 rear threads.
Fitting Will Likely Be Required
The front of the upper receiver has a trunnion that holds the front in position. The rear of the upper is held up by a spacer. I’ve seen it called the “Flat Rear Spring”, “Sear Spring Holder” and “Rear Spacer”. Regardless of the name, it’s height matters a great deal.
Velocity Firearms calls this rear spacer the “VMAC9 Flat Rear Spring”. It sets the rear height which is critical to smooth operation. This must be sitting flat at the rear and may need to be bent either closed or open a tad to set the height.
See those two holes on the right? The top is where the end of the recoil rod sits and the bottom is for the ejector rod. The upper receiver is sitting on top of the flat spring. The top hole is for the recoil rod and the bottom is the ejector rod.
This is the bolt but it is sitting on it’s side – the left side is face up and the bottom is in the shade. The important thing is to look at the rods – the recoil rod with the spring is at the top and would be at the top in the firearm. The bare steel is the ejector rod.
So here’s the problem – the bolt is moving front and back in the upper tube. It’s vertical travel is limited. The rods are vertically aligned at the rear by sitting in the holes in the receiver. If the upper, bolt and end of the rods aren’t sufficiently aligned then the bolt will bind as it moves towards the rear.
Why was my bolt binding?
Well, I hinted at the problem above. My flat springs were sitting on the bushing of my Practical Solutions 1913 rail adapters. When I racked the slide back, the alignment issue was so bad that the bolt would jam open at the rear plus the upper did not want to go back into the raised portion of the lower.
I write these posts after I build firearms and may seem like I have things figured out but let me assure you – at the time, I was having a WTF? moment. I somehow wound up talking to Sam Schneider, who owns Practical Solutions, who is a class 2 manufacturer specializing in MACs and Class III firearms. He has a wealth of knowledge about the MACs and explained the importance of getting the vertical spacing right. My “flat spring” sitting on the bushing of his adapter was throwing everything off when the bolt travelled backwards.
Ahhhh … That made sense. The bolt is at the mercy of the upper’s channel and it also rides the recoil and ejector rods that are spaceed by going into the back of the receiver. Of course it would make things bind up if they were off.
So, after talking to Sam, I knew I needed to fix this. I would cut a slot so the “flat spring” could sit flat plus it would cradle the oblong bushing so it could be tightened.
I used my calipers to find the center and then mark the offset on both sides so I cut out the notch with a Dremel. I deburred it when I was done.
I noticed some welds in the corners that I ground down out of the way.
Once the notch was done, and the welds were gone the spacer could sit flat.
At this point, it cycled better but I could still feel it binding just a bit. The last step was to crush the flat spring just a bit in my vise to lower the upper a bit further.
This took me three or four tries – I’d squish the flat spring just a bit and then test fit and cycle the VMAC. By the last time, it felt really good so I called it even. The trick is to not rush and just bend it a little bit followed by testing. I bought a couple of spare flat springs just in case.
Summary
There are a lot of MAC/VMAC upper options out there. Make sure your flat spring is seated on the bottom of the lower and is at the right height. If you feel binding, odds are it is too high and you can see this because the upper is hitting the top rear of the lower and not wanting to seat fully. Just take your time and bend the flat spring and test over and over until it fits.
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.
The defacto standard rear connector for braces and stocks on large format pistols is the 1913 Picatinny Rail adapter. The concept was pioneered by Justin McMillion and his firm JMAC. The idea exploded and now tons of companies offer adapters, stocks and braces to do just that. So, when I started planning my VMAC9 builds (they are basically MAC-11 9mm firearms), I knew I wanted a 1913 rear rail for flexibility.
Vendors of Adapters
A3 Tactical, Practical Solutions and Stormwerkz were all contenders because I used different products of their’s in the past. The A3 Tactical and Stormwerkz designs are similar – the are aluminum and cradle the rear to limit movement. The Practical Solutions model is a thick chunk of carbon steel welded at a right angle but does not cradle the rear.
I went with the Practical Solutions model because it is steel and I figured I could compensate if there was movement. Any design with a single mounting point is at risk of moving/working loose over time.
This is the Practical Solutions 1913 adapter for semi-auto pistols.
My Problem
Now, I did run into a challenge. The Practical Solution’s adapter needs to sit flat against the back of the receiver and that assumes the rear is at a right angle from the bottom. For whatever reason, none of my receivers had a rear at a right angle — all were slightly off.
The hole the bushing goes into is oversized presumably to allow for a wider range of fitment. Iou can move the adapter all over – left/right, front/back and angles but there is only the one screw/connection point.
Combine the loose fitting bushing on the botttom andthe back of my VMAC9s that weren’t square and the adapters would never stay tight.
Now, I did experiment and had two braces on each of the pistols and one stock on the carbine. They all acted like lever arms and I could easily get their mounts to turn. Let me show you what they looked like:
This is a carbine with a 16.7″ barrel and has a Midwest Industries 1913 to buffer tube adapter with a Magpul ACS stock. To be honest, that combo has a length of pull over 10.5″ that is just past the limit of what I like and I am exploring other options.
This is a pistol with an 11.25″ barrel and a SB Tactical TF1913 triangle folding brace. It makes for a nice setup at 9.5″ long.
This is a pistol with a 5.4″ barrel and a SB Tactical FS1913A aluminum strut brace that is 9.25″ long. I definitely like the length of this one too.
The Solution
I knew the primary issue as the irregularly shaped receiver back. The way to fix it was to mix up glass reinforced epoxy and “bed” the adapter so it could sit flat.
A second decision was whether to make this nearly permanent by epoxing the adapter directly to the receiver. I decided against that – at least for now – in case I decide to change or repair something. This decision to make what would more or less be a gasket between the two meant that I would spray release agent on the surfaces so the epoxy would cure but not adhere to the parkerizing.
Purely FYI – parkerizing makes an ideal surface for weapons finishes and epoxy due to all of the “nooks and crannies” it creates. If you don’t use some form of release agent, the bond is stunningly good and will only come off with heat.
For general epoxy work lately, I’ve been using PC Products’ Super Epoxy translucent model 502 dispensed from a 50ml cartridge. Cartridge dispensers are a bit more expensive but boy are they convenient. To use a cartridge, you need a gun and then tips – you can get everything off Amazon very cost effectively.
They do sell a black epoxy but I’ve been using the translucent epoxy and can dye it the color I want. Despite the gimmicky sounding name, I’ve been using it for a little over a year now. The working time before it hardens is 15 minutes and mostly cures in 3-4 hours with a complete cure of 4-7 days. This stuff has proven itself for me for general use.
By the way, In general, I would recommend you stick with a known brand of epoxy and the longer it takes to cure, the better it tends to hold up over time. Fast 5-15 minute cure epoxies tend the break down over time when exposed to repeated shocks – sometimes called “sugaring” where you can see the epoxy breaking down into small pieces.
The Steps
Apply the release agent to the receiver and adapter and let it dry. I use Mann’s Ease Release 200 – that’s what I use with the molds for my furniture also. If you read about release agents guys use when bedding rifle actions in stocks, you can see guys have used various forms of wax, etc.
To make the bedding compound, I put the epoxy and 1/32″ milled glass fibers in a cup and sti. The glass fibers help to reinforce the epoxy. You don’t need a lot of glass fibers – maybe 25% of the volume. As you increase the volume of glass fibers, the thicker the material is. In this case, I really just want the fibers to reinforce the epoxy so I went with about 25%.
To make it look decent, I added in black dye so it would blend in and not be so obvious.
I thoroughly mixed everything.
I apply the material using nitrile gloves and a plastic knife.
Acetone can be used to clean up any extra exposed epoxy until it cures.
Once everything is position correctly, I tightened down the screw on the bottom and let it cure. made sure everything stayed positioned correctly and checked for any runs or drips. Again, stuff like that can be cleaned up with a rag with acetone on it until it sets up.
Once the material has hardened, I put the part in a 150F degree oven to cure faster. With epoxy, hard to the touch does not mean fully cured.
The results seemed perfectly acceptable. If they loosen up again, then I’ll consider next steps. For now, they seem solid.
The results felt rock solid. Time will tell.
Summary
I like the Practical Solutions adapters. Bedding them made for solid connection points for braces of stocks.
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.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.
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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