Tag Archives: AK47

Add Length of Pull to a Yugo M70, M72 or M76 Wood Buttstock WIth A Limbsaver Recoil Pad

Normally, I like the length of the Yugo M70 and M72 buttstocks. They’re shorter than many Western fixed stock designs but I’ve just grown accustomed to the length of pull (LOP). Recently, I had Two Rivers Arms build me a M76 designated marksman’s rifle (DMR) and found the stock to be a tad shorter than what I wanted to get in position behind the big Vortex Hog Hunter scope I had bought for it.

Two Rivers Arms custom built Yugo M76 rifle with a RS!Regulate scope mount and Vortex Hog Hunter scope. The UTG rings have been replaced with an American Defense mount and the cheek piece will be replaced but you can get an idea that this is a big rifle and a big optic.

I realized that to make the LOP longer, I had two options. My normal route with an AK is to install a stock adapter and either go to some form of modular stock. In the case of the M76, I really wanted to stick with the original wood. The brought be to my second option – to add a recoil pad.

There are a ton of recoil pads on the market but as far as I know, nobody makes a direct replacement recoil pad for the Yugo military rifles other than me and my pad is a copy of the original. This gives you two options also – either cut the stock and install a “grind to fit” pad that would ruin the original stock or to go with a slip on pad.

Slip on recoil pads are designed to fit a certain range of buttstock sizes based on the height and width. They may not be the best looking of options but they get the job done and don’t require any modifications to the underlying stock — plus for folks who don’t like messing with tools – they can be slid on and off usually very easily.

End of Buttstock Size for Yugo M70B1, M72B1, and M76 Rifles

Zastava made the Yugo rifles but is now in Serbia and makes both commercial and military rifles. The dimensions I am about to give so you can get the proper pad only apply to he military rifles. If you have a Zastava N-PAP for example, your stock is much smaller and I don’t know the dimensions.

If you do have a military sized Yugo M70B1, M72B1 or M76 then the following should sizes should be approximately right:

  • Top to bottom of the buttstock overall: 4.48″ so just under 4-1/2″
  • Left to right at the widest point: 1.29″ so just under 1-1/3″

So that means a slip on buttpad needs to accomodate those dimensions and will slide right over the original recoil pad as well.

Limbsaver by Sims Vibration Labs

Years ago, I happened across Limbsaver recoil pads and started using them more than Pachmayr, which is another leading brand. I’ve had very good luck with Limbsaver so they were my go-to when it came to the M76.

They have a new Air-Tech series that adds 1″ to the LOP and is also remarkably spongy to absorb the recoil. The M76 really doesn’t have a ton of recoil so my decision was more based on the 1″ LOP.

The AirTech slip on pad comes in four sizes:

  • “Small” fits stocks measuring 4-1/2 x 1-1/2 inches to 4-13/16 x 1-5/8 inches
  • “Small/Medium” fits stocks measuring 4-5/8 x 1-9/16 inches to 5-1/8 x 1-3/4 inches
  • “Medium” fits stocks measuring 4-13/16 x 1-5/8 inches to 5-1/8″ x 1-3/4 inches
  • “Large” fits stocks measuring 5-1/8 x 1-3/4 inches to 5-3/8 x 1-7/8 inches

Given those dimensions, I opted to buy the “small” size and it fit beautifully.

The small-sized pad slid right on and fits nice and snug.

I actually wish they had a pad that added about 1/2-3/4″ of pull as that would be perfect. The end result is just a tad longer than what I would dial in with an adjustable Magpul PRS stock but it definitely feels better when I start lining up behind the scope. It’s staying on the rifle!


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What To Do When Your AK’s Barrel Is Too Big For Your Front Trunnion?

A few years ago, I bought a 1969 Polish Radom Circle 11 AKM kit from Arms of America. It has laminate furniture, matching parts and they populated a new Polish Chrome Hammer Forged (CHF) barrel with the front, gas and rear sight blocks. Furthermore, it was headspaced. I double checked that before I pushed out the barrel pin and then the barrel – that’s where things got interesting.

Pressing Out The Barrel

I have a 30 ton H-style hydraulic press with a 20 ton air-over-hydraulic bottle. The thing is a brute and have used it many, many times over the years on gun and car projects. There are a few things you learn over the years – 20 tons is 40,000 pounds and is a serious amount of pressure – steel parts can bend, break or even shatter under those loads. You learn to go slow, watch carefully feel the pump and listen. I also learned long ago to use the air to move the ram quickly but always do the real work by hand for those very reasons – I’ve bent the crap out of stuff in years past because you can’t tell what is going on.

I wear a full face shield when working with a press. I’m not joking when I say things can go bad fast when there is a lot of pressure. When you push out a barrel, you just don’t expect a ton of pressure from a new kit – at least I don’t. I’ve had some real hairy barrel pins and barrels in years past when dealing with surplus… but not on a new kit with a populated barrel … not until now.

Pressing Out the Barrel

As you can guess, the barrel did not press out easily. I had to apply a boatload pressure – way more than average. So much that I put a 3/4″ piece of plywood between me and the trunnion/barrel assembly. I was also checking and double-checking that my barrel press tool squarely on just the barrel and not a part of the trunnion – guys I was nervous.

I reached the point where I knew I was squarely on the barrel and something had to give. I was whacking on the press trying to shock the barrel out and I kept upping the pressure – pump, whack, pump, whack… Finally the barrel came free like a gun shot. Guys- do you remember the old Romy kits where the pins and barrels sometimes felt like you were taking your life into your own hands? That’s what this felt like.

I actually inspected the front trunnion very carefully looking for cracks. I then inspected the chamber end of the barrel – nice and smooth – remarkably smooth. No signs of galling. Ditto on the inside of the trunnion. I suspect that someone was using some kind of press system that included a barrel support and slammed that new barrel in using a level of force I couldn’t do without damaging parts. I noted to myself that reassembly was probably going to be just as colorful.

Building The Kit

Nothing new about building the kit – I had fun. In the below photo, the front trunnion and rivets are just sitting there. I was mocking things up and they are not actually set. I installed the trigger guard taking care to orient the selector stop properly and using a rubber band to keep the assembly together as I used my press and an AK-Builder trigger guard rivet jig to do the job.

The rubber band keeps the receiver down on the trigger guard jig so the rivet, selector stop and trigger guard all stay in place while you move around. The AK-Builder jig really does a nice job.
Here, everything is drilled and seems good to go.

So let’s get back to the main point of this blog post and why you are probably reading this – what do you do when the interference fit is too tight and the barrel will not go into the trunnion all the way.

Life Got Colorful Trying to Press The Barrel Back In

Yeah, that tight fit came back to haunt me. I tried polishing the trunnion and applying non-seize. Usually this works for me but when I went to press the barrel back in, it would not go. I saw the barrel begin to deflect in the press and immediately stopped. Let me explain what I mean by deflect – a material will bend so much and spring back into place. When I saw the barrel begin to deflect, I immediately stopped – it was taking way too much pressure and I was risking bending the barrel permanently. It was time to press the barrel back out and rethink the situation.

Here’s my barrel and my receiver. I double-checked the barrel to make sure I did not bend it – I got lucky. I always get worried if I see the barrel start to deflect/bend — they don’t always return to true.

So, what this confirmed for me was the someone slammed this thing together – hard. An AK barrel is press fit into the trunnion. To do this, the barrel is a tad bigger than the hole made for it in the trunnion by about 0.0010-.0026″ (0 .025-0.065mm) according to Robert Forbus who is a true machinist and has shared a ton with the AK community – click here for his page). At the tighter end (around 0.002″) it is getting hard, if not outright impossible, for someone to press the barrel into the front trunnion without the proper specialized barrel press equipment that supports the barrel. I have a big press but nothing to properly support the barrel in these high-pressure situations. It would likely warp like a wet noodle if I just kept adding pressure.

I don’t own a machine shop but I am a redneck with a shop. I needed to open up the barrel channel in the trunnion and opted to use an OEM brand brake hone. Why? Because I’ve used these small bore hones in the past for other things and was pretty sure it would work for this too.

I also need to point out that I have no way to accurately measure the barrel or the trunnion so I figured I would remove a bit and try to install the barrel, remove a bit and try, over and over until it went in. The next picture shows my OEM hone (and the Lisle is virtually identical):

This is an OEM Tool brand brake hone and the Lisle unit looks virtually identical.

Take a look at the above picture – by tightening the knurled nut at the base of the spring, you can apply more and more pressure to the 220-grit stones at the end of the arms. (The Lisle tool’s stones are 240 grit purely FYI – not a big difference.) I just used the basic pressure and did not increase it. Life lesson for me years ago – it’s easier to take more material off than it is to put it back on.

I applied cutting oil to the trunnion liberally and then slid the hone in and out with my drill on slow speed. I would do this for a bit, clean stuff, and then tested how far the barrel goes into the trunnion by hand and then keep removing more. This is not the time or place to get impatient.

By the way, OEM makes fine 400 grit stones that you can swap into place and use to polish the interior further if you . I got the job done with the 220 grit stones and silver Permatex anti-seize compound. If I ad the 400 grit stones handy at the time, I would have done so but I did not. Also, be sure to clean out the grit/dust before you try to reinsert your barrel.

My one action photo and it was blurry! You get the idea. Keep it lubed with the cutting oil and keep moving the unit in and out so you are polishing the whole barrel channel.

This is a down and dirty “git ‘er done” approach and will make machinists cringe. I go slow and test — I would push the barrel in, test and the press it back out if need be. [Click here to see how to make a barrel backout tool].

*IF* you see a bur or squished rivet protruding in the trunnion, then carefully grind that down with a Dremel and polish with the hone. Don’t try to do it all with the hone or you will be removing material elsewhere that you may need – the arms are spring loaded and independent so they will go where ever they can. This is a pro and con.

After a couple of tries, the barrel went all the way in with the press. To be safe, I confirmed the head space using real Manson brand 7.62×39 gages (use real gages folks and treat them well – don’t go cheap). The barrel headspaced just fine so I pressed in the pin and finished the rifle up.

Bottom line, a brake hone can help you carefully remove steel from the front trunnion and get a tight fitting barrel to go in. It worked wonders on this 1969 cold warrior that is now ready to go to the range.

The 1969 Polish AKM rebuilt and ready for the range!
The rifle is wearing one of our Polish Tantal/AKM grips as a 922r compliance part – we make them by hand here in Michigan from a glass fiber reinforced polymer.

Click here to learn more and order one of our Polish Tantal/AKM grips.


One of our fire control group retaining plates. that fits all AKMs and rifles that use standard AKM fire control groups.

It also has an ALG fire control group – they are awesome triggers – and one of our fire control group retaining plates. Click here for our fire control group retaining plates.


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Video: How to build an AK47 from scratch part 6 (the last part) by usmcdoc14

This is his last video in the six part series.  He recaps what he did and shares with you some of his tips for sandblasting such as putting foam earplugs in the chamber.

Here are the links to each segment – when you click on them they will open in a new tab:


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Video: How to build an AK47 from scratch part 4 by usmcdoc14

In this fourth installment, you can see usmcdoc14’s welding results and he discusses how to trim the top rails.  Note, a lot of flats and receivers now have pre-cut top rails so you only need to trim them if they look like what you see in the video – big, wide and straight.

Here are the links to each segment – when you click on them they will open in a new tab:


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Video: How to build an AK47 from scratch part 3 by usmcdoc14 [He is doing a weld build]

   

Now in this video he shows how he does the actual welding of the front trunnion.  I will definitely post some videos on how to do rivet builds also.  For guys looking to build authentic AKMs with sheet metal receivers that is the route to go.  I’m not disparaging weld builds – I’ve done at least three that I can recall.  For home builders you have three methods and they all work if you take your time to learn and then build them the right way – rivets (the traditional and proven best approach for full-auto military use), weld builds and screws.

Here are the links to each segment – when you click on them they will open in a new tab:


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Video: How to build an AK47 from scratch part 2 by usmcdoc14

  

Here is the second video in usmcdoc14’s series about building an AK using a flat.  He still swears left and right (which I find hilarious – when he said “sandblast the shit out of them” I started laughing) and gives you some good recommendations on checking the past receiver stub from the kit.  He talks about his approaches for weld and rivet builds.  He does make one comment I don’t agree with.  To press out the barrel from the rear trunnion you do not need to remove the rear sight block (RSB) – you just push out the barrel pin out and then press the barrel out.  Second, and this is just my opinion, with a weld build I would still drill some holes where the rivets were at and do plug welds otherwise you are going to pour on a ton of heat, may still not get good penetration and risk ruining the heat treat of the trunnion locking lugs.

Other than that, I think it is a good video and worth you watching and learning from.  Your best bet is to watch multiple guys and decide what works for you.

Here are the links to each segment – when you click on them they will open in a new tab:


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Video: How to build an AK47 from scratch part 1 by usmcdoc14

 

A few guys have contacted me wanting to learn more about how to build AKs from kits.  Many of the resources I learned from when I started way back when (ballpark in 2006) are now gone.  I do recommend AKFiles and their gunsmithing section so check that out.  We really didn’t have Youtube then and when I did some research I found some great videos for you to watch.

A gentleman on Youtube, usmcdoc14, put together a four part series.  This is part one and is 29:58 long.  He swears left and right and I got a real kick out of watching and listening to him:

Here are the links to each segment – when you click on them they will open in a new tab:


If you find this post useful, please either buy something using one of the links to eBay and Amazon. With Amazon, if you click on one of our links and then buy something else – even unrelated stuff like clothes, electronics and groceries – we get credit and it would be hugely appreciated. Doing something like the above will help us fund continued development of the blog.


Converting a milled M70 receiver stub to a stamped receiver front trunnion using plug welds

I miss building AKs – I never have the time any more.  At rate, some years back I wound up with two Yugo M70 front milled stubs, and then decided to convert the rifle to a stamped receiver because I liked working with AK-Builder flats.  So, in the spirit of trying something new, I decided to convert a stub to a trunnion and plug weld it in place vs. trying to machine the rivet seats inside.

Yes, I’ve heard tons of people say not to weld them together and that rivets are better.  Yes, rivets are better and I have done many of them.  Have I ever had problems with a weld build where I filled plugs, stayed away from the locking lugs and was careful with the heat?  No, I have not had any problems.  I have an AMD-65 with tons of rounds through it that still runs fine.  My thinking is that I am not firing full auto, not using grenades, don’t use this in combat … I’m not really stressing it.  What would I use for a reliable build vs. a test like this?  I’d use rivets.

This was almost eight years ago.  I found the photos and thought you might like to see them.

Here are the front stubs.

When you look at the front stub, you can see readily it could become a trunnion.

Here’s a Hungarian AMD trunnion next to it.

Here are the stubs from a couple of angles.  I already used my bandsaw to cut the top one

Ok, time to make some chips.  It’s secured an I’m milling the OD under the top shelf of the trunnion that sticks out over the receiver:

I didn’t have anything to cut the slot with for my mill so I clamped a straight edge and then ran a Dremel wheel down it over and over until I got the depth and width needed for the stamped receiver to to slide into:

My theory was that by drilling holes and filling them via plug welds that I could lock the receiver into place.  Thus, I drilled holes for the plug welds both in the stamped receiver and into the newly made trunnion:

The plug welds were done with a Harbor Freight 220V MIG running ArCo2 gas and .030 wire.  I let it cool down after each weld and was careful not to pour on a ton of heat.  Notice the relatively big weld area to distribute the load.

I then sanded it all down with a flap sander.  The back was just a regular M72 rear trunnion that I found at R-Guns. I never had problems with cracking, etc.  The experiment seemed to work for a casual use semi-automatic rifle.

That’s all I have as far as photos go.  I hope maybe it gives you some ideas.

Writing this makes me wish I had time to build another AK but it’s back to our grips and handguards 🙂


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