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Stick
Board policy mandates I state that I shoot for BCM. I have also done work for 200 or so manufacturers within the firearm community. I am prior service, a full time LEO, firearm instructor, armorer, TL, martial arts instructor, and all around good guy.
I also shoot and write for various publications. Let me know if you know cool secrets or have toys worthy of an article...
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I have a ARP bolt on my 6.8 aprox 1k rds on it.
So far so good!
For a 5.56 duty gun, I would chose Colt/BCM parts
C158 is very hard to get in small lots, and 9310 is a substitute. 9310 is not quite as good as C158 for a bolt, but, it is not a bad material.
Bolts are weak spots on ARs, and I am very open to the concept of improving on the 50 year old mil spec design - the KAC E3 bolt seems clearly better.
Even Colt has advanced bolt and carrier designs which outperform the mil spec - and they submit them to things like the IC competition and M4 product improvement - but they just cannot put them into the existing contracts.
There is no doubt that better than mil spec bolts are real, but this particular one was probably not tested as much as a company like KAC would do simply due to the cost of 200,000 rounds of ammo.
I agree that the KAC E3 bolt is probably the pinnacle of current AR15 DI bolt innovation. I would love to use one if it didn't require that special barrel extension.
I'm currently running a Rainier Arms mil spec bolt (made of actual Carpenter 158 steel) and am very happy with it...no plans on changing it, in fact. Just curious about the new design around the cam pin hole (added material) and the 9310 steel.
Rsilver's can you give me a quick-but-cogent explanation of how 9310 is different from Carpenter 158? It's been difficult finding legit factual info on the topic. My search-fu has failed in producing any meaningful commentary on what actual makes the materials different.
Like I said, I'm fully confident that a fully mil spec Carpenter 158 bolt is GTG for the foreseeable future.
In the end, you need to make bolts from various alloys and then just shoot them - and look for peening and headspace growth over 10,000 to 20,000 rounds per bolt. It is very expensive to do such tests, but we do. I am aware of no alloy better than C158 for AR bolts. There may be some, but they are not 9310.
I also, as a sanity check, called Carpenter and asked their applications engineer on his opinions for using one vs the other on an AR bolt (Carpenter sells both materials). He could not see any possible way that 9310 was better than C158 for this application.
I am not sure of the issues related to increasing the diameter around the cam pin hole, but I would be concerned that the Superbolt seems to mention the dry-film lube on the cam pin. Seems like he is saying the fit was made tighter than normal so it seems like it has a reduced ID also.
Last edited by rsilvers; 12-03-11 at 02:31.
Thank you sir.
I did not realize that Carpenter sells BOTH. I glossed-over the blurb about mating the cam pin for the first time.....I agree that the ID of the cam pin hole must be reduced to the absolute minimum of the allowable spec...maybe even slightly smaller.
There are so many un-answered questions about the superbolt as well. I have learned that the heat treating process is precise and can easily be ****ed-up if somebody does not do it right. Same with the shot-peening. A Mil spec bolt is a known quantity.
If the superbolt is not using a superior material and it's not verified if any post machining processes have been performed at all....then I'd say that from a real-world perspective it seems like it doesn't have much to offer.
What do you think about a Carpenter 158 bolt that retains the greater outer diameter of the superbolt and also some of the radiusing of the bolt lugs to increase surface area?
Is there anything that would prevent a bolt made from Carpenter 158 from being machined to those design criteria?
I like the idea of certain changes using radii to make a C158 bolt last longer. I don't know if the larger OD will interfere though - I have not looked at that. But I am not stuck on mil-spec. For example, I know that nitriding a barrel - at least when done correctly (and not everyone does), is better than chrome-lined. I am open to nickel-boron, but only if it is does a certain way, and as far as I can tell *NO ONE* does it the way I think is correct.
Shot peening is very important, and should specifically be done to ASTM B851 specs. MPI is not important at all and I am actually offended by the stupidity of it.
Last edited by rsilvers; 12-03-11 at 02:36.
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