Several things from the Fulton Armory FAQ:
[url]http://www.fultonarmory.com/[/url]
What's the best type of M14 Receiver: forged, cast, or from-billet?
by Walt Kuleck
What're the differences among forged, cast, and from-billet M-14-type receivers?
First, please note that M1A is a registered trademark of Springfield, Inc. and can be used only by them to
describe their M14-type rifle.
Most M14-type receivers are investment cast; among them: Springfield, Inc., Armscorp, Smith. There's the new
Entreprise Arms receiver that's supposed to be machined from a billet (a solid hunk of steel). There have been
offers of forged receivers but to the best of my knowledge none ever made it to market, save one: the
PolyTech/Norinco M14S.
Of course, even cast receivers are machined after coming out of the mold, as are from-billet and forged receivers.
The M1 and M14 were designed to be machined from forgings. The sections and dimensions were designed for
the forging process. It's difficult to cast the thin sections of the receiver rails, for example, without distortion. That's
why Ruger Mini-14 receivers look so clunky: they were designed to be cast.
My personal belief is that forged receivers are potentially strongest, followed by billet and then cast.
However, that's only part of the story. More salient than some theoretical strength limit is the qualiy of the receiver:
its dimensions and geometry. That's why Fulton Armory is so "down" on Fed Ord receivers. Check the Fed Ord
entry in the FAQ.
Correspondingly, that's why Fulton Armory is so "up" on Chinese receivers (though the rest of the rifle is junk): the
geometry is wonderful. Again, check the FAQ.
When push comes to shove, Fulton Armory recommends Springfield, Inc. as having the best balance of quality
and availability. Springfield, Inc. stands behinds its products and will make right something that's wrong. You can't
get that kind of service from the People's Liberation Army.
Hope this answers your question!
--Walt Kuleck
Addendum from Clint McKee:
In any case, do not buy a rewelded receiver/rifle, no matter who says so. Unless ofcourse, you want a display
piece (read this as wall hanger).
M14 type receivers are *case* heat treated to (if mil spec) 60+ Rockwell "C". This is commonly known as "file
hard." The case heat treat is 12-18 thousandths deep, with the core dropping to 28-35 (or so?).
This issue has been repeatably addressed. When welding such a material (8620 steel) heat treated to a case of
60+ Rockwell "C", the weld will create micro fractures (best case) or other stress fractures that will result in
possible/likely cracking of the receiver. Very Bad!
Why do or buy such a thing?
--Clint McKee