I see that PSA has their NiB BCG on sale for $89 (normally $199). My interest is primarily for ease of cleaning and maintenance.

EDIT: there are actually two versions of the NiB bolt carrier group:

SKU 516446914 “Premium BCG NiB with C158 Bolt” normally $149, now $89.

SKU 7791928 “Premium BCG NiB with 9310 Bolt” normally $199, now $89.

Of note is the different metal used for the bolt itself. Milspec bolts are Carpenter 158, while this particular PSA BCG (and some others) uses a bolt made from 9310. AFAIK the bolt carriers are 8620, and that’s just fine (and Milspec) for a carrier.

I’ve also seen bolts/carriers made from Ti.

Faxon seems to have adopted 9310. Young’s, Colt, DD, and BCM have continued with the the proven Carpenter 158. LMT has an AerMet 100 bolt, which is supposed to be the newest hotness.

The claims for 9310 seem to be 7 to 8% stronger, less brittle, and more durable (more resistance to fatigue).

Does anyone know who makes the PSA NiB BCGs? ToolCraft?

ANOTHER EDIT: seems there is also a

”SKU 516445123 PSA Freedom NiB BCG with 9310 Bolt”

This message has been edited. Last edited by: striker1,

I don't know. But for what it's worth. I do have one of their NiB with C158 Bolts. I've put maybe 1,000 rnds down range with it and have had zero issues.

For the rest of it... Don't know.

It has been quite a while since I read a lengthy materials analysis of the differences between the two and their suitability for use as an AR bolt.


Boiled down to, they are both quite suitable.

Interestingly enough the same study suggested that High Pressure Testing prior to magnetic particle inspection may be detrimental to bolt life in some cases, as an overpressure event beyond what the bolt is intended to regularly handle can initiate stress cracks that would otherwise not exist due to manufacturing.


I am a fan of nitride myself. I don't have any nitride bolts but I have several nitride/melonite carriers and I favor it over NiB.

That being said, all my phosphate and chrome carriers work just fine.

Its a wash. 158 is milspec (old spec) and 9310 seems to be more modern and likely more durable. If the bolt breaks, PSA might even replace it for free, so I dont think it matters.

What's is going into? The shorter the gas system, the more stress on that bolt. If you are putting it into a rifle, it's probably not worth the extra scratch for the better alloy (a milspec bolt is rare to break in a rifle). If it's going into a carbine gas system, maybe it is.

I only have one NiB BCG (by FailZero), and love how easy it is to clean. It also feels smoother when you cycle the action, so it probably is more reliable when things get dry and dirty. But all NiB is not created equal.

quote:

Originally posted by DamageInc:
What's is going into? The shorter the gas system, the more stress on that bolt. If you are putting it into a rifle, it's probably not worth the extra scratch for the better alloy (a milspec bolt is rare to break in a rifle). If it's going into a carbine gas system, maybe it is.

I only have one NiB BCG (by FailZero), and love how easy it is to clean. It also feels smoother when you cycle the action, so it probably is more reliable when things get dry and dirty. But all NiB is not created equal.

If I were to get one it would end up in a midlength.

quote:

Originally posted by striker1:

quote:

Originally posted by DamageInc:
What's is going into? The shorter the gas system, the more stress on that bolt. If you are putting it into a rifle, it's probably not worth the extra scratch for the better alloy (a milspec bolt is rare to break in a rifle). If it's going into a carbine gas system, maybe it is.

I only have one NiB BCG (by FailZero), and love how easy it is to clean. It also feels smoother when you cycle the action, so it probably is more reliable when things get dry and dirty. But all NiB is not created equal.

If I were to get one it would end up in a midlength.

So this is for a new build?


I was eyeing this upper. Great deal.

http://palmettostatearmory.com...g-ch-5165448422.html


For that price, buy that upper and the carrier that you want, and sell the phosphate carrier for $89.

I bought two of them and put them in my two PSA AR-15's and they run great and are easy to clean.

quote:

Originally posted by IndianaBoy:

quote:

Originally posted by striker1:

quote:

Originally posted by DamageInc:
What's is going into? The shorter the gas system, the more stress on that bolt. If you are putting it into a rifle, it's probably not worth the extra scratch for the better alloy (a milspec bolt is rare to break in a rifle). If it's going into a carbine gas system, maybe it is.

I only have one NiB BCG (by FailZero), and love how easy it is to clean. It also feels smoother when you cycle the action, so it probably is more reliable when things get dry and dirty. But all NiB is not created equal.

If I were to get one it would end up in a midlength.

So this is for a new build?


I was eyeing this upper. Great deal.

http://palmettostatearmory.com...g-ch-5165448422.html


For that price, buy that upper and the carrier that you want, and sell the phosphate carrier for $89.

If not for the cancer + bills, I’d have bought that already. Just wishful thinking now...

quote:

The shorter the gas system, the more stress on that bolt.

You say that but I am guessing it doesn't matter in real life. If it did I would think you would find different and improved bolt spec's among the many reliability programs that have been happening over the life of the US M16 M4 program. And I don't see that. So maybe there is some other source of good data? or a program that I didn't properly understand.

quote:

Originally posted by hrcjon:

quote:

The shorter the gas system, the more stress on that bolt.

You say that but I am guessing it doesn't matter in real life. If it did I would think you would find different and improved bolt spec's among the many reliability programs that have been happening over the life of the US M16 M4 program. And I don't see that. So maybe there is some other source of good data? or a program that I didn't properly understand.

I think perhaps this is an issue only for those who game, run guns very hard in training in adverse conditions (high heat, dirty, rapid fire) or otherwise shoot tens of thousands of rounds.

The more I think about it, the bolt material isn't a big deal as long as it's at least a minimum of C158. Replacement bolts are fairly cheap.

I do like the idea of ease of cleaning, and the "slickness" of the action doesn't really matter to me.

Aermet 100 is way overkill for the application and waaayyy spensive Lucy. Sexy and spendy.
The car-tech 158, 9310, or 8620 are all more than up to the task. They're all low carbon case hardening grades developing high core strength and toughness, with 8620 being the "lowest alloyed" of the bunch. Look at the nickel content on all three grades.

An old fart once told me (way back when) that 9310 was THE transmission gear steel, before American made trannies went to shit using 8620 because its quite a bit less expensive.

quote:

Originally posted by hrcjon:

quote:

The shorter the gas system, the more stress on that bolt.

You say that but I am guessing it doesn't matter in real life. If it did I would think you would find different and improved bolt spec's among the many reliability programs that have been happening over the life of the US M16 M4 program. And I don't see that. So maybe there is some other source of good data? or a program that I didn't properly understand.

Your guess is wrong. Talk to an armorer if you don't believe me. Broken bolts are quite common in the M4, and rare in rifle length. It's not just the added pressure, but the timing. The M4 is trying to extract before the brass has contracted, which is putting more stress on the bolt (and also the reason for the O-rings on carbine extractors, which are not needed on rifles or middies).

Also, the Army is well aware of the weakness of the M4 bolt. "Another 2011 M4 PIP announcement identified a need for an Improved Bolt and Bolt Carrier Assembly for the M4 and M4A1 carbines."
https://www.defensemedianetwor...-program-conclusion/

I don't know what their current maintenance schedule is, but it used to call for bolt replacement at 5k rounds on the M4. There was never scheduled replacement for M16 bolts; just replace as needed.

It's not an easy thing to fix, because you can't really strengthen the bolt much without redesigning the entire bolt carrier (other than a stronger alloy, which is basically a band-aid).

I have a Sharps Rifle Company XPB.

Paid around $140 for it. It has some great features and is made out of S7 tool steel, the strongest of those listed in this thread.

The DLC coating is also harder than Nib and Nitride.

I'm not saying spend an extra $40-$50 on a BCG but you should check out the SRC XPB

quote:

It's not an easy thing to fix, because you can't really strengthen the bolt much without redesigning the entire bolt carrier (other than a stronger alloy, which is basically a band-aid).

My point exactly. The bolt material does not make a hoot of difference in the overall reliability.

quote:

Originally posted by heisrizn:
I have a Sharps Rifle Company XPB.

Paid around $140 for it. It has some great features and is made out of S7 tool steel, the strongest of those listed in this thread.

The DLC coating is also harder than Nib and Nitride.

I'm not saying spend an extra $40-$50 on a BCG but you should check out the SRC XPB

Carpenter AerMet100 is far tougher than S7. When machine tools previously made from S7 are made instead from AerMet100, the tools last 12 to 20 times longer.

quote:

Originally posted by striker1:

quote:

Originally posted by heisrizn:
I have a Sharps Rifle Company XPB.

Paid around $140 for it. It has some great features and is made out of S7 tool steel, the strongest of those listed in this thread.

The DLC coating is also harder than Nib and Nitride.

I'm not saying spend an extra $40-$50 on a BCG but you should check out the SRC XPB

Carpenter AerMet100 is far tougher than S7. When machine tools previously made from S7 are made instead from AerMet100, the tools last 12 to 20 times longer.

You've found a BCG made from AerMet100?

quote:

Originally posted by heisrizn:

quote:

Originally posted by striker1:

quote:

Originally posted by heisrizn:
I have a Sharps Rifle Company XPB.

Paid around $140 for it. It has some great features and is made out of S7 tool steel, the strongest of those listed in this thread.

The DLC coating is also harder than Nib and Nitride.

I'm not saying spend an extra $40-$50 on a BCG but you should check out the SRC XPB

Carpenter AerMet100 is far tougher than S7. When machine tools previously made from S7 are made instead from AerMet100, the tools last 12 to 20 times longer.

You've found a BCG made from AerMet100?

No, of course not. I was referring to the metal itself. I've only heard of AerMet100 bolts.