As posted by Firebase, and reposted with his permission:
To rivet, you need to make yourself up a tool like this. It's what squeezes those solid steel rivets that hold the trunnion to the receiver. Barrel Pin and Barrel Removal
The best build duplicates what the factory has done, the rivet build. Why risk drilling into your chamber trying to do a screw build?
This one is the barrel pin. It's the first place I start in getting the barrel out of the trunnion. I tapered and heat treated a piece of rebar to take tons of pressure and supported the trunnion and barrel so as to not cant the rear sight base. That pin finally popped loose and what a sound they make!
Here's another Romanian with a very, very tight barrel pin. The type of pin that makes you want to just drill it out. Even this one popped loose. I found a rock steady way of holding the trunnion as I crank the press up to all 12 tons. I clamp the rear part of the trunnion tight in a drill press vise with a 1/2" block of steel under the barrel pin area. There is a hole drilled in that block so the barrel pin can pass through it.
Look! Here's that troublesome little pin. No banging, no drilling, no cursing or bloody knuckles. Now the barrel can ease on out.
Set your barrel up like this under the press ram. The trunnion is supported by blocks that span the press. I have two pennies on the face of the chamber, a small piston wrist pin (which is super hardened steel) under the ram. This is much easier to press out than that small barrel pin.
Here's the barrel free from it's trunnion. Now we can later do some riveting to the Tapco bent up flat.Front Trunion Removal
Take that front trunnion with torched receiver piece still attached and grind those old rivet heads completely off. Use something smaller than a rivet shank to punch through the trunnion whats left of those rivets.
The front trunnion is out and ready to rivet into the new receiver, which I'll be working on tomorrow. Good night for now!Front Trunion Riveting
With so many different receivers and kits on the market, You really should begin with a receiver that has no trunnion holes. Then the order of build is:
1)Rivet in trigger guard.
2)Slide in front trunnion until it fits against inserted magazine, be sure it's properly latched in. Then measure, mark and drill the 6 correct size holes.
3)Once front trunnion is rivetted, the rear trunnion location can be determined by using the top receiver cover to measure back to the groove in rear trunnion. Mark, measure, and drill these four holes.
I've been building with some known variables, as these are receivers that I make, so I chose to show my build in this order.
This series is geared for the beginner who would like to see dismantle of a parts kit, and some rivet techniques.
Okay lets do some rivetting. Take the new receiver and trunnion.....
Place trunnion into new reciever, line up rivet holes and push rivet in.....
Now, take that modified bolt cutter, place both jaws over each end of the rivet, and keeping everything straight, squeeeeeze that sucka!
See how rivet squeezer can reach into that trunnion....
Rivets get nice and flat on the inside of trunnion....
The rivet squeezer needs to be dimpled out like this to support the rivet head. Rear Trunion Removal
I will cover the removal and installation of the rear trunnion into the new receiver.
Remove the torch cut rear section with buttstock from your bag of goodies. Grind off all four rivet heads completely without going all the way through the receiver shell.
Now you can pry both sides of receiver away from the trunnion and pull it free. Now remove buttstock from trunnion if attached.
Now to prepare the rear trunnion, both rivets have to be removed. There's no way around this, so what I do is use a slightly undersized sharp drill bit and drill completly through the rivets using a press. Don't forget to center punch those rivets so the bit doesn't walk.
Now, what's left of the rivets can be punched through and out of the trunnion.Rear Trunion Riveting
Slide that trunnion into your new receiver until the holes line up. Push one of those long rivets all the way in 'til the other end sticks out the other side of receiver.
This technique varies by builder, but I will show one way of pressing the rear rivets.
I place the receiver in a bench vise, with the rivet head supported by a dimpled out piece of angle iron on the one jaw. Tighten the vise 'til the straight end of the rivet shank almost flattens to the diameter of a rivet head. Now do the same thing with the second long rivet.
The end of the rivet that was almost flattened in the vise can now be given a somewhat button shape by taps of a hammer and punch around the edges.
Now that the front trunnion and rear trunnion are rivetted to the receiver, I will begin to cover the 5 trigger guard rivets tomorrow as I remove and replace during this live build as it unfolds as Volume III, The Trigger Guard.Trigger Guard:
Here is last installment of the rivet process. All that is needed once again is the drill press, vise,grinder, punch set and hammer.
To get started, clamp the trigger guard with torched receiver piece into a vise with inside of receiver part facing up. Grind all 5 rivet stubs completey off, be careful not to grind through the thin receiver into the safety selector stop plate.
The receiver piece may fall loose at this point, pull it loose and discard. Bring the trigger guard over to the drill press, secure it firmly in a drill press vise. Be sure to center punch all five rivet ends. Using an undersized drill bit, drill 2/3 of the way into each rivet. This relieves some of the rivet tension when you set up to punch them out.
Clamp the trigger guard into a bench vise, and using a punch that fits into each drilled hole, the rivets are easily tapped out.
This is where you should now be, with safety selector stop plate and trigger guard ready to place on new receiver.
Place trigger guard, with safety selector stop plate, under it, onto the receiver. Be sure that stop part is facing upwards on the selector side of receiver. I begin with the one rivet that is all by itself on the pistol grip side.
Now, get some solid support under that rivet because you're going to take a punch and hammer and flatten the rivet protruding on the inside of the receiver.
Place the last four rivets completely in their holes..........
......and once again, from inside the receiver, using the punch and hammer, flatten and expand the rivet ends.
Be sure to get some good support under both sides of trigger guard as these rivets are being pounded. I straddle the receiver between two pieces of angle iron that are on top of 40lb bars of lead.
With all that work now behind, I call this receiver done!
I will get another black coating on it to cover all those fresh shiny rivets, then begin putting the barrel back in, which will be the next installment as I cover this in Volume IV. Pressing the Barrel and Barrel Pin
This is the last phase of finishing a completed barreled receiver.
I begin with polishing that barrel pin with 400 grit paper to help it slide in smoothly. Sometimes these things get galled as they are pressed out. Let it spin in the drill press and hold paper against it.
Get muzzle end of barrel ready by removing the slant brake. Push in spring loaded retaining pin while turning brake clockwise to remove.
First you must align the rear sight housing on the barrel with the recess of the trunnion it mates to. I'm good at using the "eyeball it" method, works each time so far. Then the barrel gets tapped into the trunnion with a plastic mallet to get it started. I use a generous amount of RCBS case lube on the chamber end of the barrel and barrel pin. It does a terrific job of helping to slide things together.
We're back to the press to make it all happen. Muzzle end of barrel goes under the press ram, use two pennies to protect it.
The trunnion is supported by the edge of the presses cross bar. I use the two solid areas just behind the barrel pin. Then I press the barrel in until the rear sight housing is close to touching the cross bar of the press.
To finish the pressing, I move the trunnion up to this one solid area, and once again rest it on the cross member. Look through the barrel pin hole and stop pressing when the notch in barrel is in perfect alignment with hole.
Just like removing the barrel pin, support the barrel where the rear sight housing is pinned on and trunnion edge so as not to have anything touching the rear sight housing, or rear sight block will be canted during the pressing. Get pin started in hole by tapping it in. Using just the press ram, push it in until ram is close to touching trunnion.
Use something made of hard steel about the size of the barrel pin and continue pressing until about a 1/16" of the pin is left protruding. I know one thing, this pin will now be a lot easier to remove in the future.
There's that barrel pin put back in just the way I found it. The barrel is now in, barrel pin is in and all the hard shop work is done. Give yourself a pat on the back!
This is the completed barreled receiver and the end of my series. Just find an AK-47 fieldstripping guide somewhere to put the rest of your goodies onto and into the rifle. All you'll need from here on out is a screw driver and maybe the needlenose pliers to get the fire control parts put in.
Thanks for your interest!