What are the most common failure modes of the AR15?

[okie]

Parts I've replaced due to wear or failure-
-Extractor spring
-Action spring
-Hammer spring
-Gas tube
-Gas rings
-Bolt catch
-Bolt catch roll pin

A friend replaced a worn barrel

A few questions if you could give more details:

On the hammer, was that on a blowback PCC by chance?

The gas tube, how did that fail?

And the bolt catch, did that fail at the same time as the roll pin? What happened to it?

[CrowCommand]

User error...

Thanks for your useful input.

I keep a LPK, gas tube, barrel and spare bolt on hand. Worst failure I've experienced as of late was a blown gas ring (rifle still functioned), and a double feed. I try to shoot 2 times amonth, at least 200 rounds per session. 11.5" pistol (no SBR here) for drills. 14.5 for longer range. The gas ring failure was under 3k rounds, but was a poverty pony (Anderson) rifle.....lesson learned, I run Colt now.

[Clint]

Sounds like the makings of a new rifle!

I keep a LPK, gas tube, barrel and spare bolt on hand.

Early gas ring failure is often associated with a rough finish on the gas ring run portion of the bolt carrier bore.

The rough finish is technically "out of spec" and tends to show up in lower quality units.

Worst failure I've experienced as of late was a blown gas ring (rifle still functioned), and a double feed.

The gas ring failure was under 3k rounds, but was a poverty pony (Anderson) rifle.....lesson learned, I run Colt now.

[SonOfAGunn]

Sounds like the makings of a new rifle!



Early gas ring failure is often associated with a rough finish on the gas ring run portion of the bolt carrier bore.

The rough finish is technically "out of spec" and tends to show up in lower quality units.

I've got a DD bcg that stopped having the rings support the weight of the carrier after less than 500 rounds. It's the chrome version of their bcg. Not sure if that matters.

Sent from my SM-N960U using Tapatalk

[MistWolf]

A few questions if you could give more details:

On the hammer, was that on a blowback PCC by chance?

No. Both were on a 16" 5.56 AR different guys at different ranges had light strikes. I had my parts kit with and replaced both for a nominal fee and got them back up and running.

The gas tube, how did that fail?

The knob end that goes into the gas key was worn beyond allowable limits. I've replaced one or two of mine and one or two of my brother's.

And the bolt catch, did that fail at the same time as the roll pin?

Yes. Yes, it did.

What happened to it?

The pivot pin hole in the bolt release was slightly over large. With use, the hole elongated and the roll pin started to shear. This was exacerbated by the mag release being not tightened enough (Mag release was on me. I was experimenting). Replaced the bolt release and roll pin and tightened the mag release. Hasn't been a problem since.

[Joe Mamma]

This is the first I'm hearing of the retaining pins. Would like to get more info on that if anyone can elaborate. Do they just lose their spring from being taken in and out so much, or do they actually break?

I think they do break, but I think the issue is the different levels of quality out there. I think any firing pin retaining pin from a reputable manufacturer/seller will rarely be a problem unless there is a problem with the gun.

Some people use regular cotter pins which I believe don't fit as well (because of a rounder head) and are not as strong (because some/all are not heat treated). I think this is where some of the reported problems come from.

I've never replaced a firing pin retaining pin, but keep some on hand in case I lose one when cleaning. But, I've never lost one either.

Joe Mamma

[okie]

No. Both were on a 16" 5.56 AR different guys at different ranges had light strikes. I had my parts kit with and replaced both for a nominal fee and got them back up and running.


The knob end that goes into the gas key was worn beyond allowable limits. I've replaced one or two of mine and one or two of my brother's.


Yes. Yes, it did.



The pivot pin hole in the bolt release was slightly over large. With use, the hole elongated and the roll pin started to shear. This was exacerbated by the mag release being not tightened enough (Mag release was on me. I was experimenting). Replaced the bolt release and roll pin and tightened the mag release. Hasn't been a problem since.

Any idea what kind of round count on those hammer springs?

And what was the round count on the gas tubes? I've always heard that those will outlast the barrel. Also, what did the gas keys look like? I'm assuming too much gas was escaping and you were getting short stroking?

[Disciple]

Early gas ring failure is often associated with a rough finish on the gas ring run portion of the bolt carrier bore.

The rough finish is technically "out of spec" and tends to show up in lower quality units.

Does this smooth out with time (and new gas rings) or does such a carrier continue to cause premature ring wear throughout its life?

[Clint]

No, don't expect this to resolve itself with use.

It is essentially a chrome plated file or rasp with surface harness over 60HRC.

Chrome is very wear resistant and gas rings don't stand a chance.

This is another example of the importance of starting with a quality BCG.

Does this smooth out with time (and new gas rings) or does such a carrier continue to cause premature ring wear throughout its life?

Early gas ring failure is often associated with a rough finish on the gas ring run portion of the bolt carrier bore.

The rough finish is technically "out of spec" and tends to show up in lower quality units.

[okie]

No, don't expect this to resolve itself with use.

It is essentially a chrome plated file or rasp with surface harness over 60HRC.

Chrome is very wear resistant and gas rings don't stand a chance.

This is another example of the importance of starting with a quality BCG.

I want to scream every time someone tells me their $80 BCG is milspec and therefore just as good. There are a million little things they don't know they don't know.