I hear these parts mentioned as spares worth having. I have never experienced a failure of either, nor have I seen someone else have problems with them. Has anyone here replaced either of these, due to wear or breakage? In the field repair context, I have an entire bolt. I have seen a bolt break a lug.

In other discussions about internal parts wear, I have mentioned the fact that I don't have tens of thousands of rounds on any one gun, or one bolt. That being said, it's likely that none of my internal parts have been used enough to see the effects of wear on certain pieces.

Are there other pieces that ought to have the more regular replacement schedule that we assign to things like action springs, hammer springs, cam pins, gas rings, and firing pin retaining pins?

In regards to the extractor, what wears out first: the grabbing edge, or the spring/insert/donut?

And has anyone ever broken a firing pin, or seen one broken?

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

I've only ever broken a charging handle roll pin.

Dig up Pat Roger's article on Filthy 14. It was an intentionally abusive test designed to prove a specific point about the AR-15/M16/M4 FOW. What makes it relevant to your question is that he documents the round counts that correspond to failures of the extractor and bolt lugs. He reported no ejector failures.

A couple other pieces to consider, the overall configuration of the rifle, firing schedule and quality of the parts themselves.

Different gas systems and ammo combinations can accelerate part failure. A carbine length case system with 5.56mm ammo was demonstrated to break parts quicker than a mid lenght with the same ammo in one of the .mil tests. Different spring and washer configurations are also recommended based on rifle config M4 vs M16 spring for example.

The firing schedule or tempo is a major piece. If you really want to break parts of weapon, run it full auto. High round count courses that emphasize rapid strings of fire also exacerbate issues. I've been in classes where rifles that had ran fine for years developed feeding issues during a string of fire.

And of course, the quality of parts. Though I have noticed that the number of companies that use quality parts has increased over the years.

Probably not what you're looking for, but I've been through two ejector springs and pins on my CMMG radially delayed 9mm carbine. The delayed blowback action is apparently quite hard on them. Thankfully, they're mil-spec AR-15 parts, so they're cheap and easy to replace. I've never broken either on a DI rifle.

I'm assuming we are talking 5.56. My 9mm's eat parts. But in 5.56 I have broken the following parts enough to consider them weak points... Bolt lugs (I have lots of spare bolts) and extractor (including the small parts needed).
I have worn out buffer springs as shown by the length measurements that are suggested.
I have replaced cam pins because the wear just seems excessive, but no failure.
I have broken gas rings again no particular failure but inspection found the issue.
I have broken a hammer pin but it was an aftermarket trigger (Geissle) so don't know if that counts.
AR's are pretty darn tough.

quote:

I'm assuming we are talking 5.56

Yes.

quote:

and extractor (including the small parts needed)

Do you know what caused the failure? Was it merely prolonged normal circumstances? What were the observed failure or wear characteristics?

I’ve seen the tooth for the extractor break more than the spring/donut.
Gas rings wear out
Bolt lugs break
Bolt Cam Pins break
(That might screw up the firing pin???)
The bolts for the carrier come loose and cause gas issues


I don’t know if there’s a maintenance schedule for the parts. I just routinely inspect my stuff when I clean it.
I made my own parts kit for the AR, and it’s in my cleaning kit.
A few extra gas rings, an extra bolt, 2 cam pins, a few firing pin retaining pins, extractors and the pins… it’s one of those “just in case” things.

So, hrcjon and CPD SIG, did the extractor failures happen before a bolt lug failure? In general, can we expect to experience an extractor failure before a bolt lug failure? If not, then it seems to me that only a spare bolt assembly would be needed; not extractor parts.

I agree though. Just in case, because you never know. Even if a certain part isn't known to break until a typical time, that doesn't mean it won't break sooner due to some sort of defect. I intend to invest in a couple extractors, outside my spare bolt assemblies.

I appreciate everyone's feedback.

KSGM- I couldn't tell you.

The Bolt Lug were on weapons in the Marines and Department Weapons for my Dept.
Only two on personal weapons I've seen, and they had a decent amount of rounds through them with some hard use (One guy was always hitting training classes with 1000+ rds a week, and it was an older Colt).

Extractors were more spread out, and I don't think there was any correlation between failure of the extractor and a broken bolt lug. I think it was more so using steel case rounds.

Again, outside of gas rings, I don't think there's a "Replace this every 20,000 rds" schedule of maintenance.

My spare parts kit is exactly for what you've said: "Just in case, because you never know". And possibly to leverage a beer or two out of it, because when you're out with your friends and one of theirs goes "PBFFTTTT", and you got the part in your bag "Hey, you owe me a beer"

Extractors can be replaced if they break. Bolts should be inspected for cracks periodically. Going off memory bolts can last as little as 5000 rounds if shooting suppressed fullauto from a 10.3” barrel, up to 15-20k rounds if shooting longer barrels with longer gas system unsuppressed and at a low volume of fire.

All of the repair, maintenance, and replacement schedules are in the Army M4 and cqbr TMs.

I stock a bunch of bolts, gas rings, firing pins, firing pin retaining pins, barrels, buffers, buffer springs, among other small parts.

quote:

Originally posted by 92fstech:
Probably not what you're looking for, but I've been through two ejector springs and pins on my CMMG radially delayed 9mm carbine. The delayed blowback action is apparently quite hard on them. Thankfully, they're mil-spec AR-15 parts, so they're cheap and easy to replace. I've never broken either on a DI rifle.

CMMG has an upgraded beefier ejector spring for their radially delayed blowback systems. It's available on their website.


https://cmmg.com/spring-ejector-mk10

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

CPD SIG implies that the extractor failures he's seen were aggravated by steel cased ammo. If everything the gun's eating is brass, I wonder if (excluding the possibility of a faulty part) there's any sense in replacing a failed extractor.

If, using JoshNC's recollection of bolt life, we figure a bolt is good for 5k rounds in the suppressed MK18 application, and an extractor (for discussion's sake) will shit the bed at 4,500 rounds, I think there'd be little sense in replacing the extractor.

I suppose this is all trivial. I am not looking for a reason not to have an extra extractor on hand. It's be good to have a few, for the likely rare case of a faulty part breaking far before it ought to. But, if we could get an idea on extractor life, relative to bolt life, we could potentially use the information to turn a failed extractor into a more efficient, proactive bolt assembly replacement.

My brother has an old Bushmaster carbine (w/ a carbine length gas system) that has over 13000 rounds thru it. For reference, I know this because he only uses it in training classes and it is kept at my home. I track the round counts on all of the firearms in my home.

That rifle has only had the gas rings replaced at approx 8k rounds. The extractor is somewhat worn (no steel cased ammo used) but it still extracts. No issues with broken cam pins, lugs, or ejectors/ejector springs. The only issue the rifle has is that it will not lock the bolt to the rear on MagPul Pmags. USGI aluminum mags are fine. This is obviously due to the shape of the notch at the rear of the Pmags. Gen 3 mags have the 'squared' notch like aluminum magazines, whereas the Gen 1 and 2 have the V/U shaped notch.

Contrast that rifle with another carbine-gassed carbine that sheared a bolt lug at just 5k rounds. Go figure. Although lug sheared, the gun still functioned. The bolt was replaced and no further issues noted.

Another carbine-gassed carbine broke a bolt at the cam pin hole at 10k. Bolt was replaced and no further issues noted.

Lastly, I have never had any issues with ejectors on any AR15 or M16 that I owned/were issued in my 40 years of shooting them.

Sometimes stuff runs forever, sometimes not.

EDIT:

KSGM, as far as extractors, my rule is that it gets inspected when the rifle is cleaned. A piece of spent brass can be used to see if there is enough 'meat' still left on it to grab a round. Obviously, hand cycling some rounds will also suffice. Also, using the generic 'o' rings or the Crane Upgrade kit 'o' rings may (or may not) accelerate wear on the extractor pawl due to the greater force imparted by the ring.

Have a spare extractor and just keep an eye on your bolt is how I roll.

Not exactly sure what happened as I wrote a long reply and it seems to not have posted. In any case let's be clear. If I have a bolt component failure its simply time for a new bolt. I'm not swapping extractors, cam pins etc. etc. Why chase the parts replacement curved if you care at all about reliability. First class bolts are $200. Ammo to break one is $5K. The broken crap just hits the dumpster. So should yours never mind extractors in the supply bin, cam pins, gas tubes, etc. Yes I get when the end of the world happens you may care, but till them have a supply of decent bolts and install...

I agree, in regards to the bolt assembly. Outside of some kind of wildly premature failure of a small bolt part, I think it's best to replace the entire assembly, if a smaller aspect breaks.

I think cam pins should be replaced at more regular intervals though. They can get galled pretty quick in short or suppressed guns. I think it'd be bad to run a cam pin through an entire bolt life cycle. Even if it doesn't fail, I think the uneven surface is likely bad for both weapon function and carrier track wear. I could be wrong though.

FWIW I'd throw a spare bolt assembly in you web gear, shooitng bag or day pack along with a spare firing pin, cam pin and firing pin retaining pin. As mentioned above, if you get bolt related malfunction in the field, it's easier to swap the whole assembly then spending time diagnosing the issue.

However, I'd still keep extractor parts, gas rings, etc. in your bench stock. I've seen more small parts, springs, rings and pins lost or damaged during cleaning then in the field. If you have extra $$ and space, a spare complete BCG is usefull. If your gas key screws shear, you can use the spare bolt until you extract the sheared screws.