How do you re-install a barrel into the front truinion?

Make sure the barrel and trunion are clean and free of burrs.
Oil them both.
Set the barrel in the trunion, align it by eye or use some fixture to line up the FSB with the front trunion.

Put an AMD65 muzzle break on the barrel to give you a flat surface to push on.
Use a mallet to tap the barrel in a little while watching to make sure it goes in straight. Be careful here and don't hit it too hard, since you are putting shock stress on the rivets...

Press it in the rest of the way with appropriate fixtures to support the trunion. Use a shop press or an I-beam furniture clamp.

I haven't tried it, but I've heard it works well to freeze the barrel in the deep freeze and to heat the receiver with a propane torch. The expansion of the receiver and contraction of the barrel is supposed to make reinstallation easier if you can get them in place before the temperature equalizes.
I've also read recommendations for using anti-sieze on the barrel where it fits into the trunnion.
I agree 100% on making sure the barrel and trunnion are smooth and free from any burrs. I intend to polish mine with fine emery cloth.

if you polish the barrel and trunion , freeze the barrel and heat the trunion with a hand held torch
you can almost push it together by hand ,, then tap with a soft hammer till the pin hole lines up..
they key is to polish the metal ..

You guys are the best...

I use TheNorms way to reinstall the barrel along with a little anti-sieze.  Works well.  Before I got my press I reinstalled one using all thread rod thru the barrel with a plate and nut on one end and the same on the rear using a wrench to tighten it and it pulled the barrel right in.  Without a press that is the way to go.

Your options are:
press
bar clamp
heat
hammer
all thread

Having tried the other methods (except the press), I prefer using all thread to pull the barrel in.  Instructions are here:  http://www.gunco.net/forums/showthread.php?t=13430

When I was building mine, when it came time to reinstall the barrel, the friend had sold his press, I tried the hammer method, it didn't work with mine, I had a pipe clamp but it didn't want to work with this situation, I was thinking about ordering the I Beam clamp to reinstall the barrel but hadn't done it yet.  I read about the all thread method a week or so back, I got a length of 1/4x20 all thread from my local lumber yard, polished the barrel some more, a thick washer in the trunnion to pull from that end, then several washers and a penny next to the end of the barrel so it wouldn't mar the end of the muzzle, at first it worked great, went in about half way and then stuck, I kept tightening till the all thread snapped!  I went back to the lumber yard and got a length of 5/16 all thread, this is slightly larger than the bore diameter, I ground it down a little bit on a bench grinder till it fit, lined it all up and started tightening, there was a pop as the barrel broke loose and started going in again, I would take it out of the vise and check for progress till it was at the correct depth.  The barrel wasn't completely straight, pretty close, I tried to turn it but couldn't, but when I put the retaining pin back in everything lined up as it should.

The all thread method is relatively cheap and works like a champ!

I heated the trunnion up in the oven to 450F for 10 minutes. It slid right on but, you need to do it quickly before it cools.

One more thing...

Be totally sure your rivets are out of the way on the inside of the trunion. I had to push out a bbl because I didn't look closely enough at a rivet that stuck out a tiny bit...

I got a press, the plinkers rivet jig and just about every other tool I could find. My first day I bent the rear sight block and trashed a brand new receiver along with my rivit jig. I not stupid Just frustrated. I am mechanicaly inclinded and some what of a gun smith(I've done 1911 builds as well as ar builds). Other than paintiance I've got all I need to build a few kits. Who has the best video out there. This is the first time I ever had to read the instruction manual before assembling anything. I'm a little embarassed to say the least...hinking.gif

I can definitely see how this could happen, sometimes it goes real easy, other time you really have to watch closely.

If you want to look at the steps that led to the disaster, lemme know how the FSB got bent, and how the reveiver got bent....I think I know how the jig got trashed, almost did that once.

The fsb got bent while trying to press out the barrel pin. I have since figured that one out. the rivit jig and the receiver both went at the same time. I thought more was better when it came to how much force to use when I set my rivits. The rivits were not squishing the way I wanted them to. So I gave the press a few more pumps to get it done. Shortly there after I was all done. I smushed everything with the press.

You need a pusher pin to get the barrel pin out, and there has to be space under the trunion for it to move out the bottom....

The Plinker jig has to be adjusted. The huge set screws in the arm have to be set so that they fit inside the trunion, but so that they push ONLY on the rivets and do not touch the trunion. The outside of the rivet (the round head) must be supported by the little block with a dimple in it.

You know what though? I think you should grab a beer and a digital camera, and do this thread proper. Once we see the crash site in living color, we can better help you decide what to do, and what your penance will be for this...

I don't know if you are a religious man or not, but you may have angered the AK gods with this stunt. I once angered the Spyderco gods so I have experience in these matters.

For what it's worth, when I tried the heat method my barrel only went about 1/3 of the way in. I lined it up, then tried the allthread method.

Long story short, I only got it done by using the bolt carrier to work against. The hole for the bolt lines up perfectly with the barrel, and the carrier mates perfectly with the trunnion. I used 2 5/8" washers at each end, and two pairs of vice-grips, with the receiver clamped (gently) in a vice. I had to line up the pin slot by hammer taps, because the barrel moved in jumps.

Where I went wrong was trying to rush through it all. The tooling came in over about a month and I just couldn't wait. I now have the proper tool to get the barrel pin out. As well as removal of the barrel. When I trashed the receiver I was trying to set the rear truinion rivits. The jig for that came in today. I tried to used the little blocks with the round dimples in them and the press. I should have waited for the proper tooling to come in but I figured if they can bang them out in caves I could probaly improvise. I'm too embaressed to post pictures but I'll say this...The receiver looks real bad, I mean REAL bad. The second one came out better. The third time can only get better. I now have all of the tools I need and I'm working on the paintence. Thanks for all the input.

We want pics of the carnage!!!!

Better to learn from someone else's mistakes than my own.

Yeah, dude, you better come clean with us by posting pics, or the AK gods will seriously harsh your gun karma.

I think the AK gods are probaly related to Allah, and I'm o.k. with pissing him off(no offense intended to any muslim members). I'll post pics soon. It may sound stupid but I have not had the time to go get batteries for my digital camera. I'll also need to be instructed on how to post pics. Promise not to laugh at me!

If it is a screw build so trunion is bare just put antiseze or grease on barrel line up trunion than just hold barrel and smack trunion on wood block on the flour and barrel goes on slowly taking 10 or 20 bangs into the wood.

I am totally new to AK builds so forgive a newbie question. If I have a de-milled kit and the barrel is in the trunion, do I have to pull the barrel out of that trunion to install the trunion in a new receiver? Or can I just rivet-in the whole assembly?

You can screw in the trunion, but to use rivits i think you have to pull the barrel. Don't take my advice though, I've been known to screw up kit builds.(at least one anyway)