So one of my ARs stopped firing! Updated 3/25/11

[imanaknut]

Went to the range today to enjoy a rare 60 degree day in December, after the first part of the month set records for cold and snow.

Played with a Norinco MAK-90 that reminded my why I am an AK-nut, that thing was right on target.

Ran the first rounds through a FrankenBeretta that I built. There are at least 8 different firearms that gave parts for this soft shooting, very accurate beast.

And then there was my Carbon-15. It has always been a fun rifle at the range, because it draws so much attention due to it's light weight. It is also very accurate and until today very reliable.

Now remember, this could happen to any AR variant, so no flames please about the Carbon-15 because at least until this, mine has been a model of what a firearm should be.

Behold the bolt!




When I took it apart I expected to find the firing pin bent, but it checked ok. In fact all other parts checked out fine, so I just need a new bolt.

About the only thing that bothered me is that this rifle has only fired about 3000 rounds, so that bolt should not have broken, but being made of metal, anything is possible, but it did get my attention for another thing to check every time I clean any of my ARs.

[TEN-32]

I've never seen that failure before, Nut. Can you tell us anything about the bolt? And what ammo were you shooting?

[imanaknut]

Ammo was good old Winchester white box made in Israel .223 55gr FMJ. I have used it by the ton and don't think it is ammo related.

Looking at the fracture area of the bolt, it appears that it possibly was bad from the factory. There appears to be tiny voids in the metal. It also appears that one side had a crack in it for a while because of the way the metal appears to have been worked smooth while the other side appears to have been torn.

I almost wish I was still working because we had a metal lab that could have told me exactly what went wrong.

[TEN-32]

I have to wonder about the composite receiver. Flex under recoil? Causing stress on other parts? Probably not, but its an odd thing.

[Mark Ducati]

WOW!

I had a DPMS Panther 16 Bull that did something similar... I broke the bolt nut that rotates in the bolt carrier assembly.

I was bump firing at the time.

[imanaknut]

Seeing the way the bolt sits in the carrier, it floats slightly on the gas rings in the back so I really can't see how even if the receiver did flex slightly it could cause this.

One thing I notice is the quality of the hole that the cam pin used to run in. The inside is so rough cut it looks like the outside of the barrel of some of the Chinese that look like they are finned but are really a rough finish cut. That would lead to thin spots in an already thin wall on the sides of the bolt around the cam pin. And amazing, that is where it broke.

I have a feeling I will never see this again in my lifetime, but it is an interesting failure.

[American Rage]

I think you should send those pics to Bushmaster and see what they say.


Rage

[imanaknut]

Can't do Rage, this Carbon 15 is an original Pro-Ordnance early serial number. I contacted Pro-Ord right after buying it and they verified it was/is an R97 built on 11/15/99.

Funny thing, I went to the Bushmaster home page to see about buying a new bolt and they don't list a chromed one. Did find one at DPMS for only a couple dollars more than Bushy wants for the black one.

[American Rage]

Can't do Rage, this Carbon 15 is an original Pro-Ordnance early serial number. I contacted Pro-Ord right after buying it and they verified it was/is an R97 built on 11/15/99.

Funny thing, I went to the Bushmaster home page to see about buying a new bolt and they don't list a chromed one. Did find one at DPMS for only a couple dollars more than Bushy wants for the black one.

I'd spend the extra and get the chrome one.


Rage

[Partisan1983]

Same thing happened to a friend of mine with his AR (It was some Colt model). Then he had the same thing happen years later in a Bushy.

[stubbicatt]

I realize that the impression is founded on data that is spotty and unreliable, but it seems to me that AR15s have many more parts failures and issues than the Kalashnikovs.

As it happens I am in the market for an AR15, this is disconcerting.

[TEN-32]

I realize that the impression is founded on data that is spotty and unreliable, but it seems to me that AR15s have many more parts failures and issues than the Kalashnikovs.

As it happens I am in the market for an AR15, this is disconcerting.

Stubbicat, I think your concerns are unfounded. As long as you go with a reputable manufacture rifle or parts to assemble you'll enjoy many years of trouble free use. There is an argument to be made for the need to keep the AR platform clean and lubed vs the AK which can run regardless.

[abpt1]

last one I bought and its very nice

http://www.spikestactical.com/new/z/...556-p-340.html

[imanaknut]

Thanks for that link abpt1!!!

[Infidelski]

3000 cycles... not good at all.

A Mag-particle tested bolt, thats interesting but may not help.

Post edit... IMHO the original was defective so the MP tested bolt may very well increase your odds of a good or better bolt. Glad it happened at the range and not some other awfully inconvenient time.

[Warlord]

Nut,

I'd give Bushmaster a call, maybe they will inspect the bolt and replace it free. Worth a shot (no pun intended).

[shadow65]

Nut, get one that is HP/MPI tested.
Delton had some bolts last year that were not properly heat treated and were causing problems.
BCG is one component I won't skimp on.

[Schuetzenman]

I haven't personally had that type of AR failure but I have seen it reported before on web sites about firearms. Frankly it's amazing there aren't more failures of this nature. Just look how thin the bolt stem or body is on each side of the cam pin hole. That bolt is the IMO the weakest link in the entire rifle design. I would suggest keeping at least 1 spare bolt around if you own AR15 rifles.

[Doc Glockster]

I haven't personally had that type of AR failure but I have seen it reported before on web sites about firearms. Frankly it's amazing there aren't more failures of this nature. Just look how thin the bolt stem or body is on each side of the cam pin hole. That bolt is the IMO the weakest link in the entire rifle design. I would suggest keeping at least 1 spare bolt around if you own AR15 rifles.

Judging from this document, it's actually common (see page 44):

http://www.dtic.mil/ndia/2006smallar...h=%22sopmod%22

[ATAK, Inc.]

Went to the range today to enjoy a rare 60 degree day in December, after the first part of the month set records for cold and snow.

Played with a Norinco MAK-90 that reminded my why I am an AK-nut, that thing was right on target.

Ran the first rounds through a FrankenBeretta that I built. There are at least 8 different firearms that gave parts for this soft shooting, very accurate beast.

And then there was my Carbon-15. It has always been a fun rifle at the range, because it draws so much attention due to it's light weight. It is also very accurate and until today very reliable.

Now remember, this could happen to any AR variant, so no flames please about the Carbon-15 because at least until this, mine has been a model of what a firearm should be.

Behold the bolt!




When I took it apart I expected to find the firing pin bent, but it checked ok. In fact all other parts checked out fine, so I just need a new bolt.

About the only thing that bothered me is that this rifle has only fired about 3000 rounds, so that bolt should not have broken, but being made of metal, anything is possible, but it did get my attention for another thing to check every time I clean any of my ARs.

Ammo was good old Winchester white box made in Israel .223 55gr FMJ. I have used it by the ton and don't think it is ammo related.

Looking at the fracture area of the bolt, it appears that it possibly was bad from the factory. There appears to be tiny voids in the metal. It also appears that one side had a crack in it for a while because of the way the metal appears to have been worked smooth while the other side appears to have been torn.

I almost wish I was still working because we had a metal lab that could have told me exactly what went wrong.

Looking at that pic, and your description tells the story. That shiny spot is where the failure started. Looks like there was a surface defect and the smooth part of the break is where the metal spalled, or fractured, then all the rough stuff is just breakage after the fact. It could have been as simple as a small ding, but I don't think it was cracked for any length of time, that was a catastrophic failure. I've done lots of failure analysis and this looks very clear cut.