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!
http://www.gunsnet.net/photopost/data/537/medium/AR_Bolt.JPG

http://www.gunsnet.net/photopost/data/537/medium/AR_chamber.jpg

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/spikes-mp-tested-chrome-bolt-assembly-223556-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/2006smallarms/taylor.pdf#search=%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!
http://www.gunsnet.net/photopost/data/537/medium/AR_Bolt.JPG

http://www.gunsnet.net/photopost/data/537/medium/AR_chamber.jpg

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.

[saleen]

I have seen that failure many times, and it has predominantly been on Bushmaster bolts run in SBRs or pistols. The shorter guns tend to be a bit more violent, and if you were using full power Q3131A, that just adds a bit more stress.

FWIW, I have never seen this failure on a bolt that has been shot-peened and MPI checked after a HP proof round. I tend to use BCM bolts and have always been happy with what they delivered.

http://www.bravocompanyusa.com/BCM-AR15-Bolt-Assembly-MPI-p/bcm%20bolt%20assemly%20mp.htm

Del-Ton is another good source, but I've never used their bolts so I can't vouch for them. Overall, however, they have a good reputation for providing high quality parts.

There's really no telling where your original bolt actually came from. It might not even be from this side of the pond.


Saleen

[imanaknut]

Thank you Saleen for that link. Haven't replaced the bolt yet but was considering the one from Spikes, but the one you link to seems as good even if it is the "wrong color".

The sad thing is the bolt in the Carbon 15 goes beyond what most manufacturers to to their bolts, The engagement lugs are rounded which is a major stress reliever. Guessing they worried too much about the lugs and not the rest of the bolt.

Thanks again for the link.

My next question, the Spikes is chrome, like the one that came with the rifle, the BCM is not. Both are peened and MPI inspected. Is the chromed one worth the $10 extra?

[AK-J]

The hard chrome probably makes it easier to clean.

[imanaknut]

After spending money on a really nice chrome replacement bolt, I come to find out that Professional Ordnance used a proprietary bolt, and that the standard AR-15 bolt doesn't work.

I called Bushmaster and found out that one of their upgrades to the Carbon 15 was to change the barrel to be able to use a standard AR-15/M16 bolt. They had a small supply of the proprietary bolts, but ran out quickly as those seemed to be the weak point of the old rifle. They have no plans on making true replacements, but for somewhere between $300 and $400 I could sent the upper in and have it updated.

Unfortunately too is Professional Ordnance also used a proprietary lug on the upper so that a standard AR-15 upper will not fit.

The person at Bushmaster recommended Brownell's as possibly having some in stock, but a call to Brownell's confirmed that I had used up my alloted miracles with them buying Beretta parts, and that they don't have the special bolt.

So now all I am left with is a bunch of parts from an early Pro Ordnance Carbon 15 Type R97...

Oh well, after a run of bad luck with a couple of odd-ball firearms, I am going to stick with the tried and true.

[romak10/63UF]

So after 3000 rounds the ar-15 bolt broke in half ? wow... just wow...:losing-it:

[imanaknut]

After doing a bit of research, it seems the bolt was a common failure point on the Pro-Ord Carbon-15s. Here is why it won't fit:
http://www.gunsnet.net/photopost/data/537/medium/Carbon-15_Bolt_head.JPG

[matshock]

After doing a bit of research, it seems the bolt was a common failure point on the Pro-Ord Carbon-15s. Here is why it won't fit:
http://www.gunsnet.net/photopost/data/537/medium/Carbon-15_Bolt_head.JPG

Wow. Round.

[5.56NATO]

Why would they go proprietary?

[imanaknut]

I can only guess that since they were using carbon fiber, which at that time was an advanced material, they wanted to make sure owners only used their parts.

One of the reasons that a "lifetime warranty" is so stupid based on the likelihood of a company being around for a long long time. In this case, Bushmaster bought them out and redid the Pro-Ord weapons to be able to use standard parts.

[Sidartha]

After spending money on a really nice chrome replacement bolt, I come to find out that Professional Ordnance used a proprietary bolt, and that the standard AR-15 bolt doesn't work.

....

Unfortunately too is Professional Ordnance also used a proprietary lug on the upper so that a standard AR-15 upper will not fit.

....

So now all I am left with is a bunch of parts from an early Pro Ordnance Carbon 15 Type R97...



I'd consider breaking the rifle down into parts and see how much money you can get out of it and invest in a Mil-Spec AR.
Since everything is proprietary it has a limited market(as you discovered) maybe die-hard fans will make it less of a loss for you.

BTW, sucks about one broken bolt trashing a otherwise good rifle.

[ready]

Maybe I missed it but you can't just change out the barrel and use a standard bolt to get back in business? What about the lower? Compatible with milspec uppers? For about 250 bucks at BCM, you could be up and running again.

[imanaknut]

You didn't miss it, we didn't discuss just changing the barrel, which is not possible without an adapter. The standard AR barrel is held in by a threaded ring. The barrel in the Professional Ordnance Carbon-15 is pressed and then pinned into the upper receiver.

I am not sure how Bushmaster modifies the upper to accept a standard barrel, and I am sure they are not willing to discuss it.

As for the lower, that I did discuss, and again Pro-Ord decided to also make the mounting lugs proprietary so that a standard upper will not fit into the Pro-Ord Carbon-15 lower.

Really a shame because it is/was a fun rifle to shoot being so light weight yet with almost no felt recoil.

I was thinking about getting a really cheap bolt, and then seeing if I could machine the lugs to something close to the shape of the Carbon-15 bolt, yet still have enough engagement to handle the loads required.

Oh, Sidartha, the Carbon-15 wasn't my only AR, and I believe I have invested in more mil-spec ARs than you could imagine! ;)

[Sidartha]

Oh, Sidartha, the Carbon-15 wasn't my only AR, and I believe I have invested in more mil-spec ARs than you could imagine! ;)
Yea but you could always use another one right? ;)

[ready]

You didn't miss it, we didn't discuss just changing the barrel, which is not possible without an adapter. The standard AR barrel is held in by a threaded ring. The barrel in the Professional Ordnance Carbon-15 is pressed and then pinned into the upper receiver.

I am not sure how Bushmaster modifies the upper to accept a standard barrel, and I am sure they are not willing to discuss it.

As for the lower, that I did discuss, and again Pro-Ord decided to also make the mounting lugs proprietary so that a standard upper will not fit into the Pro-Ord Carbon-15 lower.

Really a shame because it is/was a fun rifle to shoot being so light weight yet with almost no felt recoil.

I was thinking about getting a really cheap bolt, and then seeing if I could machine the lugs to something close to the shape of the Carbon-15 bolt, yet still have enough engagement to handle the loads required.

Oh, Sidartha, the Carbon-15 wasn't my only AR, and I believe I have invested in more mil-spec ARs than you could imagine! ;)

I just read that the headspacing is different as well so even if you were able to grind the lugs down on a milspec bolt, it still might not operate, at least not safely.

[imanaknut]

That is true about the head spacing, and one thing definitely on my check list of things to make sure is right before trying a modified bolt. What a pain, what a shame.

[5.56NATO]

Hoosiers always find a way!