ok, i demilled a polish kit and everything went well until i went to press the barrel back in.  it will not go!!!.  i've actually seen the barrel start to bow under the 12 ton press.  so i tried the "heat the trunion, freeze the barrel trick"...no dice.

today i measured the parts.  the barrel is 0.2 mm larger than the hole in the trunion.  i know that this is the barrel that came out,  it was a hard press but it come out.  

anyone ever heard of this?  

It probably bowed because it was off center. Freeze the barrel agian may some dry ice heat the trunnion and hammer it in. Use a stack of pennies taped together on the end of the barrel. Don't beat it just hit it like your taking your time putting in a nail. Also try polishing both the barrel and trunnion with some 600-800 grit and some oil.

but how did the barrel end up larger than the trunion?  could a trunion "stretch" over the barrel?  i'm gonna need some liquid nitrogen to get this thing to shrink enough to fit.

Quoted: It probably bowed because it was off center. Freeze the barrel agian may some dry ice heat the trunnion and hammer it in. Use a stack of pennies taped together on the end of the barrel. Don't beat it just hit it like your taking your time putting in a nail. POUND THAT SUCKA WITH A BIG RUBBER HAMMER! Also try polishing both the barrel and trunnion with some 600-800 grit and some oil.

Sounds like some good advice to me!

If its .2 mm, thats .0078 thousanths. ( 7.8 thousanths)
That WILL NOT go.
The two pieces should be within .0005. ( 1/2 thousanth)
Check those measurements again.
You must have the wrong barrel.   IT AINT GOIN IN THAT TRUNNION WITHOUT MACHINEING.

the barrel and the trunion should be within 5 thou for optimum interferance fit. so 8 thou is a bit much, but it can be done. best way would be to pollish the outside diameter of the barrel and inside of the trunioun and recheck measurements. try to get them within 5 thou, less will make your life easier. a very slight champfer on the end of the barrel with some high pressure lubricant will be a big help as well. and if all that don't work, slap it in a three jaw chuck and hit it with a file.

You may know all this stuff, but just in case....

I would re-check measurements....make sure your caliper is zeroed, that there are no chips in the jaws, and that you are not measuring over a high spot (like a scratch, or galled area).

Like stated above, if the bbl is not straight, it can bind up and will bow under heavy pressure. Check the barrel and make sure the surface going into the trunion is clean, and free of any marring or galling. If it is, carefully take it back down with a file, and dress with fine sand paper. If you take too much off you will not have a press fit anymore and will ruin the build. Also check to make sure there are no galled or marred spots on the trunion.

Often I dress the first 1/4 inch of the barrel a little extra so that it slips into the trunion easier. Once lined up it will press in easier.

My Yugo barrel was also noticeably larger than the trunnion hole.  I stuck it in the freezer and used liberal amounts of anti-seize on it.  Then stuck it in a 36" I-bar clamp and it went in pretty easily.

I had problems with my rivets sticking up alittle too high. I wouldn't have noticed until i pull the barrel back off and saw that it was digging into the rivet.

If you want to verify that you have the right Polish barrel, the trunnion serial number is stamped underneath the rear sight leaf.