AK Front Trunnion Riveting

[deac777]

Excuse my ignorance, I have never built an AK but I'm planning on building one and have watched the AGI video "Building the AK Semi-Auto Rifle". In the video they instruct you to rivet the front trunnion and receiver together by installing the trunnion which already has the barrel installed, into the receiver. They then tell you to cut a slit in the rivet, inset the rivet into the receiver and trunnion hole, with the slit parallel to the barrel. Then you are to hammer on the rivet head which causes the rivet to mushroom on the barrel.

Has anyone riveted their receiver and trunnion using this method? What are your thoughts on using this method?

[Baeleron]

That's definitely not the "correct" way that the combloc factories use. Plus you wouldn't have any visibility on how well your rivets had mushroomed. My vote is to just do it the right way (press barrel out, rivet, press barrel in).

[valley82]

That's definitely not the "correct" way that the combloc factories use. Plus you wouldn't have any visibility on how well your rivets had mushroomed. My vote is to just do it the right way (press barrel out, rivet, press barrel in).

Yep, if you are going to hack job it, why bother building one?

[meaty-btz]

Push out Barrel then rivet..

Rivets were meant to be set from one side.. things won't be correct if you try to PUSH it from one side.

[noozeyeguy]

Push out Barrel then rivet..

Rivets were meant to be set from one side.. things won't be correct if you try to PUSH it from one side.

This.

The rivets are pretty soft, I'd think there would be a pretty solid chance that the rivet head would mushroom outside the receiver instead of within the void between the barrel and trunnion.

Plus the only way you'd know if the rivets were properly seated would be when you fired it... probably not the best time for a catastrophic failure.

FWIW: I have only a small benchtop press for pressing barrels out; I use the allthread method for installation. Where there's a will there's a way..

[ar15barrels]

In the video they instruct you to rivet the front trunnion and receiver together by installing the trunnion which already has the barrel installed, into the receiver. They then tell you to cut a slit in the rivet, inset the rivet into the receiver and trunnion hole, with the slit parallel to the barrel. Then you are to hammer on the rivet head which causes the rivet to mushroom on the barrel.

[Twinkies]

Look up Ginsboy2003 on Youtube "improper build techniques" if you need a visual on why you dont rivet the trunnion with the barrel pressed in. It might be the easy way.. but its not the right way.

[kcstott]

Look up Ginsboy2003 on Youtube "improper build techniques" if you need a visual on why you dont rivet the trunnion with the barrel pressed in. It might be the easy way.. but its not the right way.

I'm glad this guy did a video that shows right there what kind of quality to expect. I'm sorry I can't build junk

[deac777]

Look up Ginsboy2003 on Youtube "improper build techniques" if you need a visual on why you dont rivet the trunnion with the barrel pressed in. It might be the easy way.. but its not the right way.

Thanks for all the comments and the link to the video. That video really discouraged me from using the AGI method.

[kcstott]

Thanks for all the comments and the link to the video. That video really discouraged me from using the AGI method.

And it's not that much more work to press out the barrel set the rivets and press barrel back in place. A few more tools are required but if you're going to build your own stuff it's good to have on hand.

[deac777]

And it's not that much more work to press out the barrel set the rivets and press barrel back in place. A few more tools are required but if you're going to build your own stuff it's good to have on hand.

I agree on having more tools and the correct tools. I'll be making a few tools and converting a bolt cutter to a riveting tool. Thanks for all the suggestions, and the collection of prints that you have on your web page.

[valley82]

Glad to hear that you are going to build the rifle correctly, and you might as well get the tools as AKMs become kind of an addiction. After building one and shooting the rifle you built, you will want others, I almost guarantee it.

[Builder]

Or the trunion can be welded to the receiver without removing the barrel.
When done properly, a weld is stronger than a rivet.
Enjoy the journey,
Builder

[kcstott]

Or the trunion can be welded to the receiver without removing the barrel.
When done properly, a weld is stronger than a rivet.
Enjoy the journey,
Builder

Ah No no it's not and I can prove it.
and FYI rivets will always be stronger then welds, the only reason rivets are selectively used now days is because welding is faster.

The weld would be stronger then the rivet if the receiver was 1/8" thick and mild steel but not .03937" 4130, You create a high stress area that can not flex and twist as a rivet allows for. Was it designed that way? No, it was just a lucky coincidence. looking at high speed film of an AK being shot the receiver is a limp noodle flopping around.

Not to mention if you've ever performed a proper weld on 4130 you will know it don't like to be welded, (fusions welded), without pre and post heating as you will develop cracks and Lord only knows what kind of steel the front trunnion is composed of.

Welding the receiver to the trunnion is and always will be a very bad idea.

[Builder]

Ah No no it's not and I can prove it.
and FYI rivets will always be stronger then welds, the only reason rivets are selectively used now days is because welding is faster.

There may be a little confusion here. The rivet can be cut with a pair of wire cutters, while the TIG weld can not. Which is stronger? Yup, the weld.

The weld would be stronger then the rivet if the receiver was 1/8" thick and mild steel but not .03937" 4130, You create a high stress area that can not flex and twist as a rivet allows for.

looking at high speed film of an AK being shot the receiver is a limp noodle flopping around.

Yes, and please recall the video of the fellow who put 3 wooden match sticks into each rivet hole and fired an AK twice before the match sticks sheared.

Let's play a little "If I was a PSI, how would I get out of here" game - without the gas cycling the bolt carrier, when fired, where do the forces go?
Upon firing, the forces of the expanding gases move the bullet down the barrel and exert force on the bolt face. The bolt face in anchored into the trunnion so high force of the round is NOT carried directly to the rivets. The force on the bolt face is carried to the bolt lugs which is carried to the trunnion which is then transferred to the rivets and then to the receiver and to the stock and then to the shooter's shoulder.
So only the recoil from the round and bolt carrier cycling forces are carried by the rivets.

Not to mention if you've ever performed a proper weld on 4130 you will know it don't like to be welded, (fusions welded), without pre and post heating as you will develop cracks and Lord only knows what kind of steel the front trunnion is composed of.

Actually 4130 is reasonably easy to weld and those welds are reasonably strong. Warming of the 4130 is all that is required.

Welding the receiver to the trunnion is and always will be a very bad idea.

In reality, welding works quite well.
So why was the AK47 riveted and not welded? Because TIG welding was not available in 1947.
But it is now.
Thanks,
Builder