Because why not! A .22 single shot build

[Mauser lover]

MachIVshooter, it is all your fault! I am now looking for small milling machines to show up on my local Craigslist... Weaponsguild may have helped, but you definitely are in the act of pushing me over the edge!

 

[MachIVshooter]

MachIVshooter, it is all your fault!

Blame I am happy to accept!

If we can get enough people building high quality repeating arms, the useful idiots on other side will be forced to pay attention and see the lie they've been sold for so long. Right now, they can be relatively dismissive of the cobbled together and dangerous (to the user) slamfire single shots and the like, but there are getting to be more and more of us out there capable of manufacturing highly functional automatics completely from scratch.

 

[JohnKSa]

... other than a pretty heavy trigger pull on account of the wide, deep and hooked sear engagement I gave it due to the use of mild steel for fire control parts.

You should look into case/surface hardening.

http://www.brownells.com/gunsmith-t...ing/surface-hardening-compound-prod27119.aspx

http://www.midwayusa.com/product/119479/cherry-red-surface-hardening-compound-1-lb

Pretty simple to do and would expand your capabilities considerably.

 

[MachIVshooter]

^^^^

Yeah, a useful technique for using many low carbon steels. Unfortunately, A36 is so unpredictable in it's carbon content and crystal structure even within the same piece that it's difficult to do much with it, so I'd still err on the side of caution with thickness, depth and breadth. 1018 is a better material, but when I'm buying steel, I don't really buy mild steel at all. High carbon stuff like 8620, 4100 series Chromoly and various tool steels are my go-tos, and I through harden all of it. For stainless, I like 416 for easy machining, but 440 and 17-4 are definitely better for critical parts. 304 ain't a bad frame material, though, and machines decent with sharp cutters. And then there's my love affair with 6/4 Ti.....

 

[JohnKSa]

Unfortunately, A36 is so unpredictable in it's carbon content and crystal structure even within the same piece...

Isn't that precisely the kind of issue that surface treatment/case hardening is supposed to address?

 

[MachIVshooter]

Isn't that precisely the kind of issue that surface treatment/case hardening is supposed to address?

I'm no expert on case hardening, but really all you're doing is adding carbon to the surface (a few tenths to a couple thou deep). It does nothing to alter the grain structure, and the martensitic transformation in A36 is highly irregular/unpredictable due to the inconsistencies in the matrix.

But to be honest/fair, I've never tried case hardening A36, really don't work with the stuff much outside of flat bar and square tube for simple structural things or bumpers and the like, where it's low cost, excellent weldability and ease of cutting & shaping are attributes.

I don't have a Rockwell tester, but maybe I'll give the case hardening a try with it and see how it does with the old file test

 

[JohnKSa]

I'm no expert on case hardening, but really all you're doing is adding carbon to the surface (a few tenths to a couple thou deep). It does nothing to alter the grain structure, and the martensitic transformation in A36 is highly irregular/unpredictable due to the inconsistencies in the matrix.

It won't change the overall structural characteristics of the part significantly, but if you're worried about the geometry of a sear, for example, changing as the result of wear, it will eliminate that problem.

If the sear engagement is overly conservative due to worries about surface wear then case hardening should completely fix that. If it's overly conservative due to worries that the part might bend then it's not the proper solution.