So, would you be interested in putting the barrel back in the trunnion with your hands only??
 This is what i did. I used an engine builders trick for installing valve seats and guides in Cylinder heads.  I wamed the trunnion up to about 250-300 degrees (still not enough to mess with hardness)  and stuck the end of the barrel in Liquid Nitrogen for about 30 seconds.  Then just slid her right in, and aligned the dowl pin hole and let the temps normalise for a little bit.
 SWEEEEEEEEEEEEET!!
For those of you with no Nitrogen to play with.. try this instead.  Get dry ice and crush some up into chips and put in a large styrofoam container and fill up with a few inches of rubbing alcohol.  soak the barrel in that for 3-4 minutes while warming the trunnion up.  I bet this would work as well.

sounds like it works good, i will give it a shot



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OOOOHHHHH NOOOO....I belive you might of compromised your barrel...Yes it does fit but I belive your temper might be questionalble...
I am going off from what I've been told and heard.....When you quench it that fast in sub-zero...You will change your temper...I am not a metalurgest but I would talk to one....
as for the technique you used...I have done this on bearings and races but not to that extreem like you have......I heat one part like you did and then have the other part in the freezer atleast overnight..got to work quick....
Deffinitly talk to a metalurgest...

The dry ice method is what I used when I did seats and guides in cylinder heads as well. It wont bother the barrel. It will just make it harder. They use chryogenic tempering with stuff in racing cause it makes it smoother. So its not gonna hurt the barrel at all.

Nope, no compromise.  Cryogenic freezing of engine parts and rifle barrels is a little known secret.  What cryogenics does in it converts retained austenites into Martensites. It is actually a stress relief that makes metal much stronger by tempering without effecting durabilty.
Freezing a gun barrel for this short time will not really do a whole lot anyway. True cryogenic metal treating is a much longer deal.  But, at any rate this will only help the barrels strength, not reduce it so dont worry.
 Just so you know, there are guys who do this for barrels for a fee (cryogenic freeze)

Interesting Idea.  Here's a fly in the ointment.  When you pull the barrel out of the nitrogen I can envision moisture condensating on it almost immediately.  How about greasing the barrel first?  NOPE.  The condensation is then on the grease - which is slipped into the trunnion - water, grease barrel and all.   OK, that's my 2 cents worth.  This is just a guess on my part so don't put too much weight on it.

Where can you get liquid nitrogen OR dry ice?  I'd like to give this a shot, thanks for posting!

I wouldn't think the condensation would be that bad if you're quick about it, if you're not they will normalize too much to fit anyways.  I'm surprised I never though of that *doh* we used to do this in my old shop to fit certain pins and things in, it worked great.

Quoted: Where can you get liquid nitrogen OR dry ice?  I'd like to give this a shot, thanks for posting! I wouldn't think the condensation would be that bad if you're quick about it, if you're not they will normalize too much to fit anyways.  I'm surprised I never though of that *doh* we used to do this in my old shop to fit certain pins and things in, it worked great.

You can buy dry ice at the loacl Publix here in South Florida.

With the .50 cal barrels and probably other cal. too they offer "cryo freeze" as an option to increase accuracy.

Here is a link; http://www.onecryo.com/onecryo/firearms-testimonials2.htm

Tag for interest.

Quoted: Interesting Idea.  Here's a fly in the ointment.  When you pull the barrel out of the nitrogen I can envision moisture condensating on it almost immediately.  How about greasing the barrel first?  NOPE.  The condensation is then on the grease - which is slipped into the trunnion - water, grease barrel and all.   OK, that's my 2 cents worth.  This is just a guess on my part so don't put too much weight on it.

If the trunnion is 300 deg, wouldn't it boil off any condensation immediately?

I just wouldnt worry about it anyway.  I used a high temp grease in the trunnion. If any moisture got on the barrel in the 4 seconds it took to take it out of the Ni and stick it in the trunnion i really dont think it will be an issue of any kind as i do not plan on ever removing the thing again anyway.

The dry ice method you use the pure alcohol if you can find it. it has a lit lower freezing point and will help make contact with the barrel to get it cold. Methyl Alcoho has a freezing point of  -178F  and dry ice is about -109f so in theory if you crush up a lot of dry ice, stick your barrel in a styrofoam cup (get a tall one) and fill the cup up with the chips surrounding the barrel and top off with some alcohol you should be able to get your barrel close to 100 below zero.  Wear gloves!! stuff will spew out of the end of the barrel!  at least with the NI it did until the tempslowered on the metal.  Of course you would have to let it sit in there for a lot longer than th NI trick. but it works on Valve guides, so i dont know why it wouldnt shrink up the barrel enough as well  I would say that it should work well enough to at least get it down to a rubber mallet install.  Lightly polish up the mating surfaces with a little 220 emery.  Sparingly though.   I also put a slight lead on the ballel, polishing the first 1/4 inch a bit more to get it started nicer but with the NI method it was like ..... sticking something into linda lovelace

I've heard of people using this method with dry ice chilled acetone.

I've done 2 barrels using Mapp Gas on the trunnion and the barrel was room temp in a cold garage.  It slid in noooo problem, gotta work quick though as the barrel locks in just a few seconds.  If it needs tweaking,  I then use a threaded rod (wrapped in electrical tape to protect the barrel indsides) with nuts on either end to pull it in or tap it out with a stack of pennies and an old 3/8 extension.  The 2 I've done were very easy.

Scweett setup at a good price

Now I know why I hang out in here!

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