Heat Treating Bent Metal Receiver?

[fal guy]

Is this necessary? Anyone have a gtood method?

[NagantNut]

I'm not planning on heat treating any of my bent metals. I just can't justify the cost for the benefits. I've also heard that not every country heat treated their receivers.

I'd really like to see a bent metal made of stainless with a thickness of about .050 it seems that even the .040 receivers are a little thin when compared to the rails in the bolt carrier. The added thickness and the hard stainless steel would negate the need for heat treating.

[dougjones31]

Some Stainless is softer than 4140.

I have 2 bentmetals that I did not heat treat and they are holding up fine. I put 2000 rounds through one in 1 day!
I say that they were not hardened, but when I TIG'ed the rails in....the heat might have hardened the area around the welds a little. The heat mark went down to the center support and hammer pin holes, but the other holes were unaffected.

I call it unhardenend anyway, because welding the rails is normal proceedure. :D

[NagantNut]

Hey Doug,

When you say you "welded the rails" are you talking about the upper rails or the lower rails? I believe the lower rails are already hardened, at least the ones from K-Var appear to be hardened.
I am less concerned with the lower rails wearing than I am with the upper rails. The upper rails take the most abuse and are more prone to wear IMO. The only real wear point on the lower rails is the ejector, especially if you use steel jacketed ammo.
Welding the lower rails will not harden them. If anything, it may anneal them ( make them softer). In order to harden them you would have to heat them to a bright red color and then quench them in either oil or water.

[Packrat]

The only AK I ever saw fail was a Maadi that had about 11 000
rnds through it. The upper rails at the rear of the receiver
wore, but the real problem was that they broke at the bend.
When the rifle was fired, the upward pressure from the hammer
on the bottom of the bolt carrier caused it to rise up exactly
the way it does when you disassemble the rifle. The receiver
carrier kept it from going anywhere, but it was jammed so
that you had to remove the cover and force the bolt carrier
back down until it was in position again. Then the same thing
happened at the next shot.

So it's not just wear, it's a combination of wear and metal
fatigue. The metal fatigue looked like the steel was stressed
by bending and the stresses had not been relieved.

[dougjones31]

The bentmetal Upper rails are just shaped...they are already there....I welded in the lower rails and when I welded the lower rails in....I think it hardened the metal of the receiver around the welds a little. That is what I was saying.

[flanigan]

After you have welded the lower rails in, heat the whole thing up until its almost cherry-red and quickly quench it in mineral oil (less chance of flash). You have to completely immerse it or it could warp. After it cools, clean off the oil and reheat until the metal turns blue, and allow to air cool. This will harden the metal, but cannot say for certain what the Rockwell number would be. Then you can rivet the trunnions in, park, etc.