Re: Building a Yugo M72

76
On a whim I took a look at the rear trigger guard rivets again today. It occurred to me that I could maybe use the long rivet tool I got for the long trunnion rivets. I rested the head of the rivet on the hex piece that came with the tool and used a section of 9mm rod that I'd used to try and make a bucking bar a few days ago as a ram to push on the rivet plate from the front trigger guard rivets. Worked like a champ.

That hex piece wouldn't work for the frontmost of the two rear rivets. Chopped the end of the rod off and drilled into it to make something resembling a rivet head and used that instead of the hex piece. It messed up the head a bit but it doesn't really matter since they sit underneath the pistol grip.
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Next up I need to find the long rivets for the trunnions. I'm sure I put them somewhere logical, I just don't know what I thought was logical at the time.
Then I need to put the short rivet jaws onto a set of harbor freight bolt cutters. Typical with my luck one side of the bolt cutters isn't as wide as the other side so I need a ton of filing to get the jaw on that side to swing properly.
Then its time to rivet trunnions.

Re: Building a Yugo M72

82
offensivename wrote: Sat May 02, 2020 2:41 am Goal for this coronaweekend is to finish riveting the receiver.

Ordered the barrel install tool and I've started re-researching how to rust blue, after watching an Anvil video I feel like its doable. Worst case is I spend $50 on supplies and fail
Rust bluing is much simpler than it looks. Even on the videos. Another good tutorial on YouTube is by the Midway USA feller.

My only tip, get all your parts stupidly clean from grease & oil. Get a good carding brush for taking off the velvet. Use a quality solution.

I've skimped on all those before. To my own regret. I'll post a picture of the solution I use here in a bit.


Get that puppy done. I wanna see it!
Screw communism

Re: Building a Yugo M72

83
This is the product I've used with the best results. A little goes a long way. Done probably half a dozen guns with this bottle, still almost half full.

https://www.brownells.com/gunsmith-tool ... d9815.aspx

Good carding brush.

https://www.brownells.com/gunsmith-tool ... d6762.aspx


Oxphoblu is a good cold blue. Probably gonna do my reweld with it for now. Feeling to lazy to really do anything else right now & the humidity season is upon us here.
Screw communism

Re: Building a Yugo M72

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Which ended quickly and badly with a broken drill bit inside the rivet that is still in the receiver. I have a special knack for this kind of thing apparently

Edit: Got the rivet with the broken drill bit out. luckily it was loose and some work with the dremel and pliers got the rivet out. Unfortunately thats the "easy" rivet now I need to think of a safe way to get the more forward one out that is right up against the pistol grip mount.

Re: Building a Yugo M72

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2nd rivet came out easier. Put the rear trunnion in and got the holes lined up to put the long rivets in . . . and then I remembered these are swell necks and I have to dimple the receiver. This is done to help add some connective strength between the trunnion and the receiver, it also seems that everyone has their own way of doing it, I was going to just try and use a conical center punch and a hammer but it didn't seem to really work. The internet seems to really like using a 1/4" ball bearing and pressing it into the rivet holes that need dimpling, which is what I ordered, so I actually went backwards this weekend.

Re: Building a Yugo M72

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Decided to get just a tiny bit of work done on this tonight to try and keep it moving.

I got in a package of 1/4" ball bearings this week. The sphere does a good job of deforming the receiver evenly. For the swell necks. I'm doing the rear trunnion first, then I'll redo the bottom rivets and then move on to the front trunnion.

The process I used for the long rivets on the rear was to put the rear trunnion in place (holding it in place with one of the rivets) then put a ball bearing on either end of the free rivet hole. Put it in a vice and crush. Holding two ball bearings in place while closing a vice is hard so super glue to the rescue.
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I twisted down on these till the vice head started to want to torque itself crooked. The seem to have fit the swell necks good enough.
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Some people debate the need for the swell necks and the receiver dimples with 7.62x39, I actually don't think the trunnions I have were dimpled for the long rivets, the yugoslavians sometimes just spot welded the receiver on top of riveting it but I didn't want to hunt down long flat head rivets.

Got the long rivets restuck through and I'm ready to do the crush sometime this weekend.
IMG_20200507_220356.jpg

Re: Building a Yugo M72

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Rear trunnion is finally in!

Long rivet tool did a decent job of smashing the tail into a roundish shape.
IMG_20200508_203642.jpg
Re-did the same rear trigger guard rivets with the same jerry rigged piston and bucking bar setup I used before, this time THROUGH the rear trunnion like I was supposed to the first time. Took a smidge of filing to get the holes to line up exactly right but the end result is good enough for the Portland version of the Khyber Pass.
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Re: Building a Yugo M72

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Well that was riveting! Ba-dum-tss :sorry:
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Got the front rivets in! The receiver is now (mostly) complete.

Yugos have one long rivet at the bottom front of the receiver. Then four more short ones. The long rivet is done the same as the rear trunnion rivets. The small ones inside the receiver take a bit more work. Toth Tools sells a special tool that replaces the jaws of a Harbor Freight bolt cutter set. You just adjust the bolt cutters and give them a squeeze.
IMG_20200509_121112.jpg
I also used these to dimple the bottom rivets, just put a ball bearing on the outside of the receiver and squeeze. After doing that I'm pretty sure this trunnion wasn't really dimpled to begin with and they just relied on the tack welds to hold the thing together better. Luckily 7.62x39 isn't exactly a powerhouse.

These aren't the most beautiful rivet tails, but they look like they should work fine.
IMG_20200509_122056.jpg
The only thing left is to try and get the mag to seat correctly. The safety stop I used was pretty bent up from my hamfisted attempts to demil everything so I picked up a Romanian replacement. After comparing the two I think the romanian one is just a smidge thicker than the yugo one where the rear of the mag seats, I'll take a dremel or file to it at some point and see if I can make things fit correctly.

Re: Building a Yugo M72

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Barrel tool showed up yesterday, gonna spend some time familiarizing myself with how it works then I guess order some rental headspace gauges, I might try and get at least of of the barrel in before they get here so I can spend the limited time with them adjusting and nut futzing with the entire process.

Re: Building a Yugo M72

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Dont make my mistake. Lube is your friend. Little bit of wheel bearing grease on the journals goes a long way. Trunnion, rear sight base, gas block, & front sight.

Post pics. I've only ever used a hydraulic press. So I'm curious about other methods. Maybe less barrel destroying methods.
Screw communism

Re: Building a Yugo M72

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I got the tool from toth tools: http://www.tothtool.com/AK-Bulged-Trunn ... _p_13.html

There are some videos on that page that show it at work.

Right now I'm trying to figure out the order of operations and logistics for this. The barrel I have has the handguard cut and extractor cut already, so I need to make sure its aligned properly when installing it. Its also going to be mildly difficult to increase the headspace on the barrel as is if I mess that up. Gonna keep reading and watching videos to see how others have solved this.

Re: Building a Yugo M72

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Cool beans. May have to get one of those. I've got quiet a few of his other tools.

When I set up a barrel that's already got the hand guard retainer cut made, here's how I do it. First I set everything upside down. On a good flat surface. The little tabs that are on either side of rear sight base should be what's un contact with the flat surface. Then use something round that fits the hand guard retainer cut. The shank of a drill works well. Put the round bar on the flat surface with the receiver. You should be able to start the barrel into the receiver & things should be straight.

I make it sound complicated. I'll get a picture of a mock up later to show what I'm talking about.
Screw communism

Re: Building a Yugo M72

99
Here's a rough idea of what I was attempting to badly describe.

The little tabs on the front trunnion are straight & parallel. So they make a good reference point for the receiver.

The hand guard retainer cut is straight across the barrel & "should" be a uniform depth. So a drill bit the same size as the cut will keep it in the correct orientation.

Most press in barrels I've dealt with have a slight taper or chamfer to the end of the chamber. This will allow you to start the barrel in the trunnion. Hopefully you can get it in far enough for there to be enough resistance to keep it from falling out.

My concern would be rotational forces while working the toth tool.

Hopefully this is of some help to ya. It's also a good way to get the front and rear sights in the ball park range of straight, once you get to that point.
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