How is a gun barrel heat treated?

[jd4320t]

Well, essentially my issue is that I will be casting a receiver from aluminum around a mosin nagant barrel. Obviously the heat treat of the barrel, whatever it is, will be ruined by having molten metal cast around it...Once the aluminum cools, I will then unscrew the barrel (the whole point of casting around it in the first place is just to get the threads, since there is no such thing as a MN receiver thread tap available to the public) and re-heat treat the barrel...at least that is the plan...

What are you making?

 

[kludge]

Since barrels are not tempered or hardened steel I doubt you will hurt it. I would preheat the barrel though, and after just let it cool. Even if you do hurt it, it's just a MN.

Steel barrels (not stainless steel) are heat treated and stress revealed after machining and rifling. A mill spec M16/M4 5.56 barrel is hardened to around 30 Rockwell C scale (i think the exact specs are 28 to 33 Rockwell). So technically they are "hardened" but not to the extent that most people think of hardened steel. 30 Rockwell is saw-able and file-able but much stronger than regular steel (which can vary from 3 to 12 Rockwell depending on type). The mil spec barrels are made from chromoly steel usually the 41xx series of alloy steels.

In light of superior knowledge, I retract my statement. Thanks, J10.

 

[indoorsoccerfrea]

What are you making?

My goal is to make a semi-auto, that way I can avoid the whole locking-lug issue. I haven't drawn up a blueprint yet though, just turning ideas over in my head.

 

[sloughfoot]

Making a blow-back semi-auto? What pistol round? Maybe a 32?

 

[CountryBoy19]

Well, essentially my issue is that I will be casting a receiver from aluminum around a mosin nagant barrel. Obviously the heat treat of the barrel, whatever it is, will be ruined by having molten metal cast around it...Once the aluminum cools, I will then unscrew the barrel (the whole point of casting around it in the first place is just to get the threads, since there is no such thing as a MN receiver thread tap available to the public) and re-heat treat the barrel...at least that is the plan...

IMHO, you're going about it wrong. You likely won't get a very good cast thread in the receiver. It's hard to cast fine details (like threads) with any reasonable amount of precision, especially with AL. You would be much better off casting the receiver then single-point threading on a lathe (although I'm not entirely sure that can be done because I'm not familiar with the barrel/thread/receiver you're looking to make).