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Discussion Starter · #1 · (Edited)
First off, Thank you for allowing me to join the forum. This is my first post. I am an aspiring shadetree gunsmith and have a question. Can anyone give me some insight on how to remove a barrel retaining pin from a used 91 or G3 trunion. I thought I could maybe drill the head off and use a press to push it out. But the pin is rock hard and a drill bit does not seem to even make a dent. I have already removed the cocking tube and did a fare job. It is very useable. The trunion has also been removed from the demilled receiver. I have built several AK's and a FN, now I am trying to tackle this project. I have a 91 kit on the way...Thanx
 

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You just press it out. I built a split block that closely fits around the receiver to keep it from rotating. There's another hole in my block that lines up with the barrel pin, and I use a 3/16" dowel pin to push it out with my press. Since the hole is at nearly a tangent to the receiver, it will be hard to keep it from rotating without some way to hold it down.

The first "pop" to get the pin moving is right at 5 tons of pressure, then it takes about 1 ton to keep it moving until it drops out the bottom.

And yeah, it's a hardened pin. You can drill it, but you'll need a carbide drill bit.

You'll then need a 3/16" drill followed with a 5.00mm dowel pin reamer to recut the groove in the barrel after it's pressed back in.
 

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Discussion Starter · #3 ·
removing barrel retaining pin....

Thanx for the insight. I do have a milling machine vise that I put the trunion in. When tightened, the trunion has a flat spot on it where the pin is in the right spot to push out. Because of the flat spot the trunion is tight and does not appear to rotate. I will give it a try a little later today. Thanx again!
 

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Wow, now this gives some empirical data to support how much forces these guns withstand. How did you measure the amount of force required?
My press has a big force gauge on it. Pressing the barrel itself out of the trunnion takes the same amount of force - somewhere between 4 and 5 tons the barrel will make it's first "pop" when it moves, and then 1 ton or less to press it the rest of the way out. And it's literally a pop sound that reverberates through the entire press.

What's interesting is that it only takes about 1 ton to press the barrel or the pin back in. As time passes with it assembled, the parts fuse together somewhat which is why it takes so much more force to get them moving the first time.
 

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Thanx for the insight. I do have a milling machine vise that I put the trunion in. When tightened, the trunion has a flat spot on it where the pin is in the right spot to push out. Because of the flat spot the trunion is tight and does not appear to rotate. I will give it a try a little later today. Thanx again!
If it's a loose trunnion, that might work. But you'll need something to hold it better to put it back together. Here's what my fixture looks like. The 4 large holes in the top are bolt holes that are inserted from the other side. And I have now cut some reliefs into it to clear the raised ribs on the outside of the receiver.

 

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Discussion Starter · #9 ·
RE; removing barrel retainingf pin...

OMG! you have just proven my theory that there is a tool for every job and the job is easy if you have the right tool...I would give up my first born, if you would sell me that tool for removing the barrel pin. Or how about you make another and I will buy that one. I am a twenty two year veteran of the Boeing company and I wish I had the tooling knowledge that I see somebody else has. It helps to have the tooling to make the tooling. I need to invest in a milling machine. If you are considering making a run of that tool, I would be first in line to buy one. I knew that if I registered with this forum I would learn all kinds of s__t! You guy are incredible...Thanx...rdb241
 

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OMG! you have just proven my theory that there is a tool for every job and the job is easy if you have the right tool...I would give up my first born, if you would sell me that tool for removing the barrel pin. Or how about you make another and I will buy that one. I am a twenty two year veteran of the Boeing company and I wish I had the tooling knowledge that I see somebody else has. It helps to have the tooling to make the tooling. I need to invest in a milling machine. If you are considering making a run of that tool, I would be first in line to buy one. I knew that if I registered with this forum I would learn all kinds of s__t! You guy are incredible...Thanx...rdb241
I know a few people with CNCs I'll ask about making some of them. I've made some tooling for my own uses, and there are more I'd like to make, but some of them would be very time consuming on a bridgeport like i have.
 

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I used a fluted carbide bit to drill halfway through the pin. Then whacked it out with a hammer. Worked great.
To put the new pin in I just sandwiched it between to pieces of wood in my vice (the trunnion that is) and whack the hell out of it till it seated (used a punch for the last bit)
This was done on my HK33 that I built and its been working great
 

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Some enterprising soul needs to create a business providing all of the necessary jig's for the DIY HK builders like they do for the AK and AR community.

There has got to be more than a few here that could do it.

Dave go ahead and put me down for a jig if you ever get things going. I will add it to the pile of building supplies :)
 

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Some enterprising soul needs to create a business providing all of the necessary jig's for the DIY HK builders like they do for the AK and AR community.

There has got to be more than a few here that could do it.

Dave go ahead and put me down for a jig if you ever get things going. I will add it to the pile of building supplies :)
I'm working on it. I need a CNC mill anyways, there's some fixturing I want to make that will be a total PITA on a bridgeport. And I still need to do some engraving. I've got some ideas for HK receiver build and repair fixturing that I've never seen before. Now I'll just need to make more room in the garage. If only I had enough room in the garage to put the thing.
 
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