Re: Building a Yugo M72

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No, semi. The selector arm is large lever on the right of the receiver that goes from Safe - full - semi. Or in this case Safe - nothing - Semi. If it were full auto there would have to be another hole drilled a little above and behind the middle hole in the previous image for the disconnector(?) pin.

Re: Building a Yugo M72

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I'd been putting this off because it was a bit of a moment of truth for this receiver, but tonight I vowed to finish drilling the holes on the left side of the Yugo receiver. Mostly I was a little afraid because I had had bad luck drilling out the end cap of my first form 1 suppressor a month ago, either I marked it off center or it had walked a bit when enlarging the hole and I had to buy a whole new one. It wasn't that bad buying a new $10 aluminum end cap, but buying a new $100 80% receiver is another story.

So I commenced the drilling. 5mm for the selector hole, 7mm for the hammer (left side/forward) and trigger (right side/back)
left side holes.jpg
The moment of truth came when I grabbed a pair of FCG pins from my parts kit bag. The hammer pin popped right in. The trigger was a bit harder. Eventually I took a plastic hammer and gave it a light pop and it popped right into place. I think 7mm is exactly the size of the large end of the pins (they insert from the left side of the receiver and have a bit of a retaining clip edge on that side to hold it in place. Lucky for me the holes appear to line up.
left side pins.jpg

Re: Building a Yugo M72

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Originally I had planned on just drilling the final holes in the left side of the receiver tonight, but then I decided to think a bit about how to finish the final step of finishing the receiver, cutting out the excess metal between the selector hole and the smaller hole just in front of it that lets the selector lever fit into the receiver.

The bit I'm talking about is the part on the top middle where you have one big (10mm) and one small (7.5mm) hole right next to each other.

On a finished receiver that area has a key shaped hole, so that bit of metal needs to be removed so the two holes become one. My original plan was to take my dremel to it and just use a cutting disk to remove the material. However, I was worried that since the only cutting wheels I have are about an inch in diameter that I could pretty easily slip and put a gash into a part I didn't want to. The only other option was to use a file and file away the material. I didn't want to spend 3 hours filing though, I've learned that heat treated steel is hard. On a lark though I decided to try the files. If they didn't work I would come back another day and try my hand at careful dremeling.

It turns out the files were, in fact, the perfect solution. A triangle shaped file put a nice size notch into the metal with only 30 seconds or so of filing. I kept at it with that till I'd put a good size notch in the metal, then turned to a fancy thin course flat file that had filing surfaces on the flat and the edge. That took another minute or two to break through. Then another 15 minutes of filing to bring the notch out to meet the smaller hole's diameter and form the proper shaped hole that let the selector through:
selector slot.jpg
A light tap with the hammer popped the selector in through the hole on the left side of the receiver and I was able to test out the rotation.

Safe:
right side safe.jpg
Semi:
right side semi.jpg
Next up is riveting in the trigger guard, bullet guide and trunnions. I'm not sure how I'm going to do this just yet. There are special tools out there but they cost around $100 each. I suppose I could build a second AK pretty easy once I have the tools but I'm going to do a bit more research and see if there are some easy kitchen table solutions.

Re: Building a Yugo M72

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offensivename wrote: Tue Nov 19, 2019 1:56 am I'd been putting this off because it was a bit of a moment of truth for this receiver, but tonight I vowed to finish drilling the holes on the left side of the Yugo receiver. Mostly I was a little afraid because I had had bad luck drilling out the end cap of my first form 1 suppressor a month ago, either I marked it off center or it had walked a bit when enlarging the hole and I had to buy a whole new one. It wasn't that bad buying a new $10 aluminum end cap, but buying a new $100 80% receiver is another story.
Have you tried a set of pilot drills? They are stubby drills designed to be really rigid and produce an accurate pilot hole. Look kinda like metal Vienna sausages with sharp points and a single flute. I bought them when I had problems with drilling accuracy... then found out it was the driller who was inaccurate, not the drills :|

Re: Building a Yugo M72

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bajajoaquin wrote: Tue Nov 19, 2019 10:02 am
Have you tried a set of pilot drills? They are stubby drills designed to be really rigid and produce an accurate pilot hole. Look kinda like metal Vienna sausages with sharp points and a single flute. I bought them when I had problems with drilling accuracy... then found out it was the driller who was inaccurate, not the drills :|
For most of these hard drilling tasks I do use the short length drill bits. I'm pretty sure the accuracy issue came from the fact that I was drilling a titanium end cap and my center mark was off from a little manufactering nubbin. It just made me gun shy.

Re: Building a Yugo M72

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Nothing new to report, sent an email off to a local gunsmith to see if they could/how much would it cost to have the gun parts blued. I was starting to think this is something that should be done before the barrel is populated and the receiver riveted. Hot caustic bluing is the way this was done at the factory and after reading up on it it seems like a bit much to try at home.

Also being tempted by a cheap hungarian build, $350 and no barrel populating/depopulating needed!

Re: Building a Yugo M72

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Some minor non-picture updates. I re-bought the rivets I need (my old ones disappeared) and realized that the rivet holes were placed but not drilled out in the receiver. I drilled them all out to 5/32, then realized I didn't have a drill bit for the 4.5mm long rivets, waiting on those to get here from good old McMasterCarr. I've also started the process of buying the tools I'll need to do the rivets.

Also I found a place to do the Blueing. $225 which seems better than me trying myself, screwing it up, then having to pay to do it anyway.

Also, seeing as I just bought a WASR-10 for around $500 I can safely say that building a single AK from a parts kit is in no way cheaper than just buying one. The thing that kills it is the special tools you need for rivets and barrel populating. I guess the good thing is that once you have those tools things look much cheaper.

Re: Building a Yugo M72

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Drilled the 4.5mm holes in the receiver for the long rivets that go through the rear trunnion (x2) and the front trunnion (x1). I slapped the front trunnion into the receiver to check the holes and they all lined up . . .
except for the long rivet hole. I drilled this rivet out before I had a rivet drilling jig (seriously don't do this without one, I'm paying for it) and didn't quite understand the process and filed both ends of the rivet flat and tried to drill through them. I have a hole that goes through the rivet but it isn't in the center and made it so I couldn't push out the rivet with a punch like I did for the others. I briefly considered drilling out the hole with a 4.5mm bit I have but its slightly bigger than the hole in the receiver and I realllly don't want to snap the bit off in the trunnion (I did that once in the rear trunnion and it cost me, the front trunnion is basically the cost of a new parts kit). So that means its time to break out the file and fix it the long and hand crampy way. Got a bit done before I managed to snap the file in half tonight. Luckily McMaster Carr shipping is fast and free.

Re: Building a Yugo M72

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WASR-10 for around $500? I haven't seen those prices in years.

I think that most builders build enough AKs from parts that it makes financial sense or for legal reasons. Of course, I believe that parts kits were cheaper and more available in the past.
It is an unfortunate human failing that a full pocketbook often groans more loudly than an empty stomach.

- Franklin D. Roosevelt

Re: Building a Yugo M72

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K9s wrote: Wed Jan 22, 2020 12:46 am I believe that parts kits were cheaper and more available in the past.
wasn't just about everything? yesterday i saw a $500 moisin-nagant ("it's a tula" he said, stroking it lovingly) and a similarly-priced chinese SKS. we both commiserated that we hadn't bought a pallet of 100 $100 rifles.
i'm retired. what's your excuse?

Re: Building a Yugo M72

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This one might be on the edge of worth it. New production Romanian Semi-Auto RPKs are going for around $1300 right now. If I don't count the tools that I needed anyway (drill press) I'm guessing this project will look something like:

80% Receiver w/ Engraving $154
Parts Kit: $305
Layout guide: $17
New Barrel: $180
Rivets: $9
Bluing: $275
--Total for just gun parts: $940

Extra tools that are AK specific:
Small Rivet tool: $75
Trigger Guard Rivet tool: $95
Long Rivet Tool: $155
Barrel Install/Populating tools: $140
Rivet drilling jig: $28
--Total reusable tools: $493

So its about break even (JRA was selling yugo RPKs for a while but I don't remember how much they cost). The Bluing on the Yugo is a big hit that other Aks wouldn't have.

Re: Building a Yugo M72

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offensivename wrote: Wed Jan 22, 2020 11:02 am This one might be on the edge of worth it. New production Romanian Semi-Auto RPKs are going for around $1300 right now. If I don't count the tools that I needed anyway (drill press) I'm guessing this project will look something like:

80% Receiver w/ Engraving $154
Parts Kit: $305
Layout guide: $17
New Barrel: $180
Rivets: $9
Bluing: $275
--Total for just gun parts: $940

Extra tools that are AK specific:
Small Rivet tool: $75
Trigger Guard Rivet tool: $95
Long Rivet Tool: $155
Barrel Install/Populating tools: $140
Rivet drilling jig: $28
--Total reusable tools: $493

So its about break even (JRA was selling yugo RPKs for a while but I don't remember how much they cost). The Bluing on the Yugo is a big hit that other Aks wouldn't have.
And the education you got was pretty valuable, too.
It is an unfortunate human failing that a full pocketbook often groans more loudly than an empty stomach.

- Franklin D. Roosevelt

Re: Building a Yugo M72

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Yeah, at this point I would have no problem demilling an AK parts kit and I'd be pretty confident finishing the Childer's 80% receivers. I'm probably going to get a Romanian PSL receiver just so I can have it done in case someone decides to ban 80%s or 'Scary Rifles' in Oregon, I might also pick up an underfolder receiver and maybe another fixed stock to play with in the future, I'll have all the tools so it won't be near as big an investment.

Re: Building a Yugo M72

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OOf, sad all my pictures gut wiped with the upgrade. . . maybe I'll be nice and go back through and reupload.

ANNYWAY, I finally got tired of trying to file out this front trunnion rivet and went to the drill press. Slowly drilled a little bit at a time in case I had an off center hole, after a bit I switched to the other side then POP. . .


The rivet came loose, pulled it out with some pliers and double checked that the long rivet fit. All the demill and receiver drilling should now FINALLY be complete. Gotta spend some money now and order a barrel and some more rivet tools and figure out how assembled the gun needs to be before it gets a nice blueing bath.

Re: Building a Yugo M72

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Been in contact with a gunsmith across the river in Vancouver WA who does hot bluing. I was concerned about whether the parkerized finish on the receiver and the barrel I just ordered (a green mountain barrel: http://www.gmriflebarrel.com/ak47-2gm-2 ... inned-m72/) would be a problem to blast off and he didn't think so. The only thing he was concerned with was the receiver being an 80% that I finished and how he would check it in. He thinks the serial number I had engraved should be good enough for his purposes though. If not I can get the whole manufacturer/city/state/caliber nonsense engraved on when I go to get my next project (a .30 cal suppressor) engraved.

I've also ordered up the rest of the tools I need to rivet together the receiver and trunnions. The plan of attack right now is to rivet together the receiver, trigger guard, bullet guide, and front and rear trunnions, then tote the whole mess out to get reblued, then comes the next scary part, pressing in the barrel with the correct headspace and repopulating it.

Re: Building a Yugo M72

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I've let this project sit a bit because I've been a bit perplexed on how to proceed with some challenges, but given the general order of social distancing I spent some time today trying to sort things out.

Right now the next step is to rivet the trigger guard, safety stop and pistol grip plate into place. To do this I have a tool that you rest the whole assembly on and then tighten a set of bolts to smash the rivets in the receiver. Here is the base of the tool:
tool base.png
You place safety stop on the receiver, the trigger guard on that, then insert rivets, then place it on the base (you can see where the four rivets go in the image, its the dimpled parts to the left). On a normal ak it would look something like this:
trigger guard.jpg
Problem #1 is that Yugoslavia never found a process that everyone else did that it wanted to follow exactly. On Yugo AKs there is an extra pistol grip plate that sits underneath the receiver, it looks something like this:
safety stop and pgp.jpg
That won't fit on the jig. because it sits below the receiver. Thanks Tito.

Luckily I think I figured out a solution by looking at all the other rivet tools I have for this project. One of them has a piece that has the rivet head dimple that is tall enough to sit in the jig and hold that rivet in place and sit properly. I'm pretty sure that will work, otherewise I can always do an ugly job of pounding the rivet out with a hammer and punch, the head won't look nice but it will work. Another option is to tap the guard, plate and receiver and use screws, thats not 'correct' so I only want to do that as a last resort (but why did you not just use screws Kalashnikov?)

Re: Building a Yugo M72

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As my last post implied I have more than one problem, and at least one of those extra problems is with this build.

If you were building one of these from a flat you would need a press and a welder. I don't have either which is why I'm using one of the childer's receivers that has the hard parts done. That means that I already have the rails welded onto the receiver (I'm actually unsure what order you would go about this if you were building from a flat but I assume you would normally rivet the bottom pieces together before welding the rails in).

The first four rivets I need to do are just behind the mag well cutout in the receiver which is just forward of the hammer assembly. The pin hole for the hammer is reinforced with an extra plate on the right hand side, it dips down to just above the bottom of the receiver.
inside receiver.jpg
The tool I'm using has a piece that will flatten the end of the rivets (all four at once) that is clearly designed to go underneath this.
flattening tool.jpg
That thinner part on the right seems like it should fit right underneath. The problem is it did not at all. I broke out the trusty dremel and grinding tool and got to work, making it a little thinner both width wise and height wise (the width part I ground on the left side to shrink the whole tool, the height I just did on the thin part). I can now fit the tool inside all the way.
gap.jpg
Of course theres not enough room on that right side to fit a rivet underneath the tool.

I'm still considering my options. Theres always the "just ignore the way things are meant to be and use screws." But I also think I can probably make this work by grinding/cutting this tool to only do half the rivets at a time. I don't want to fuck this up because drilling those rivets out without messing up the receiver would not be an easy task.

Re: Building a Yugo M72

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So managed to get at least some of the rivets installed. I ground down the metal piece that crushes the heads so that it would fit past the internal reinforcements. I figured this wouldn't do the best job with the crush but probably good enough. The tool basically cradles the receiver and you use two bolts to tighten down on a metal piece that sits on top of the flat crushy piece.
rivet tool.jpg
After twisting down on those two big bolts a few full rotations I ended up with this crush. On the right hand side rivets you can sort of see the ramping where the tool didn't quite reach the edge. The guard feels really tight on the front though so feels fine.
crushed rivets.jpg
But, of course there are more issues. Like I said in a previous post the grip screw area protrudes down on the yugo and theres no way to use the trigger guard tool to crush the rivet tails.
rear rivet problems.jpg
I'm not 100% sure how to get around this. I think I might just have to use a piece of metal as a bucking bar and smack the tail with a flat punch and my 3# hammer.

Re: Building a Yugo M72

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I've always used a bucking bar for those rivets on a yugo. A section of 1/2" round bar fits well & you can make a rivet head sized divot in it with a 5/16" ball end mill. Clamp that bar in your vise or in a shop press. Use what ever is handy to smash the tail of the rivet.
Screw communism

Re: Building a Yugo M72

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mattgunguy wrote: Sun Apr 12, 2020 7:11 pm I've always used a bucking bar for those rivets on a yugo. A section of 1/2" round bar fits well & you can make a rivet head sized divot in it with a 5/16" ball end mill. Clamp that bar in your vise or in a shop press. Use what ever is handy to smash the tail of the rivet.
Yeah, thats the plan as of right now. That 3# hammer I bought for this project has come in handy more times than I can count.

Re: Building a Yugo M72

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Rivets.

I hate rivets.

Tried my hand at the rear trigger guard rivet with a bucking bar in a vice, a 3# hammer and a big flat punch. Something got crooked at some point and I wasn't getting a good flat head so I decided to abort (rivets are cheap) and just cut the head off with a chisel. . . well I got MOST of the head off and managed to sort of rivet the rest down to the receiver. Its ugly as hell, but it actually seems to hold ok so I figure I might as well try and get the back to rivets on and see if they hold the plate down well enough. It doesn't hold anything mission critical so I'm thinking the worst thing happens the front rivet breaks from recoil and then it comes out without my intervention and I can try again. I need to think of a different holding technique for the receiver, this may be a job to try and get my wife to help with.

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