9310 or C158
- Thread starter Red Dawn
- Start date
Admittedly, I haven't really looked into the difference. That said, I highly doubt I will run an AR bolt to failure given my ammo budget and the few guns that budget is spread between.
Given modern metallurgy, both are probably pretty darn good... at least compared to metals made 48 years ago during the 1970s.
This ones going in a pistol I think the mil spec is better for this app. And I read this too:
Bolts are becoming a pet subject!
It is always interesting to consider the bolt within the context of its application. To do so will draw not only on stress analysis, but also on fatigue theory and metalurgy. This will quickly move the solution beyond the simple question of which steel is best, for the best steel if applied out of context will not perform adequately.
So for simple illustration let us assume that the steels are applied well, before discussing the differences.
Carpenter 158 is without doubt an excellent material for the production of M16 bolts. The material is clean with negliable elements in the make up that are detrimental to the fatigue life. It can operate happily within the confines of the enviromental requirements imposed by the application and has a very low deformation of the parts as they run through heat treatment. The down side to the material is that it was designed to heat treat in large sections so the thin bolt material will respond somewhat voilently. Again not an immediate problem if the heat treatment is absolutely perfect but within the confines of a production enviroment it will throw problems.
By comparison AISI 9310 will on first inspection also make an adequate bolt material. It has several alloy elements that promote a better structure and in the correct heat treatment will provide a slightly higher toughness than Carpenter 158 which is benificial to the fatigue life. Corrosion resistance is slightly higher but as with C158 it should not be applied without some form of surface protection. Thin section response to quenching is somewaht less than C158 which makes it better suited to the manufacture of bolts. However by comparison to Carpenter 158, AISI 9310 has several elements present in its composition that are detrimental to fatigue while not being evident in the physical properties.
It has become evident from the industry that a number of manufacturers have jumped upon the AISI 9310 wagon in order to claim better performance. While in theory an AISI 9310 bolt may perform better I would not typically select this material specification. There are a wide number of superior alloys available without resorting to the nickel based maraging alloys which are expensive, difficult to machine and extremely temperamental in behaviour. The steel industry has advanced since the specification of Carpenter 158 but the basic premises for the selection remain even if the menu has now expanded.
Bill Alexander
Well, there's added strength, and then there's an asymmetric shape. Just playing devil's advocate here... but when metal heats up it expands. Symmetric shapes expand much more uniformly than an asymmetric partial hole/socket.
Does it matter in the real world? Hell if I know.
I've heard of breaking splines off the end of the bolt- I don't know how widespread then fracturing through the cam hole is... And I'm reasonably sure I won't shoot enough ammo in the next five years to worry about it.
.. I like asking people in the smart kids club here for the answers cause they are always outside the box thinkers.
You make a great point and valid argument.
And I doubt I Shoot enough to make a difference eitherbut I am curious.
Just buy a known quality(name brand) bcg & be done with it, if you're worried about longevity. Like dial1911 said, "And I doubt I Shoot enough to make a difference either", most guys won't shoot a cheap generic bolt until it fails.
I will say that most buy the cheapest thing they can find. I will also say that I can buy Toolcraft BN bcgs direct, within pennies of the wholesale cost of no-name BN bcgs. It's just that I have to wait twice as long on Toolcraft. And sometimes they look identical.
Now I need some cheap phosphated bcgs for the budget buyers.
I will say that most buy the cheapest thing they can find. I will also say that I can buy Toolcraft BN bcgs direct, within pennies of the wholesale cost of no-name BN bcgs. It's just that I have to wait twice as long on Toolcraft. And sometimes they look identical.
Now I need some cheap phosphated bcgs for the budget buyers.
Heat will kill a bolt "quickly", long term use isn't a concern to me. Just don't run the gun until it's cherry red and you'll be fine with any of the upper tier bolts for a couple lifetimes.
And I mean relatively quickly. You'll have gas tube and barrel problems first.
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I think the added torsional rigidity of the socket type could help longevity, but unless you have a registered lower I don't think it matters.
