Bolt Carrier Failure in AR-15's

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JayPee

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I have read comments indicating that bolt carriers used in the less-than-premium AR's will break in service, while the ones used in premium guns will not. I also see a lot of recommendations to replace the bolt carrier groups in the common AR's with one from a premium manufacturer. (Note: I am not referring to a failure of the gas key or its bolts, just of the bolt carrier itself.)

Sometimes I have difficulty distinguishing between honest, authoritative, good-advice information and the bias I see voiced by Tacticool enthusiasts. Has anyone seen any authoritative reports of bolt carrier failures in rifles used in the more affordable rifles? Is there any reason to believe the BCG's in premium AR's are made of a superior metal?

I'm not being derisive of those who own premium rifles, I like them too. But I often see critical comments about the more common guns emanating from fans of premium rifles that I cannot confirm, and which are often contradicted by owners and users of the less-than-premium brands. This is one of those cases. I mean no offense to anyone.
 
The only carriers I have seen broken are following catastrophic failures of the rifle and subsequent damage of the carrier. Not the carrier's fault.
 
some cheap bolts prematurely fail at the locking lugs, but kinda rare. You shouldn't swap bolts from one gun to another after heavy use.
The M16 carriers are heavier and allow the bolt to stay locked a little longer, which allows more pressure drop. I'm not saying to only buy those carriers, just throwing the idea into the pot (flame me now)
 
LMT, Daniel Defense, CMT and Bravo have good ones. Palmetto State Armory has 2, one milspec, one not, get the Premium.

these are the specs to look for:
Milspec Carpenter No. 158® steel bolt
HPT Bolt (High Pressure Tested/ Proof)
MPI Bolt (Magnetic Particle Inspected), It should be engraved "MP"
Shot Peened Bolt
Chrome Lined Carrier (AUTO), shouded firing pin
Chrome Lined Gas Key
Gas Key Hardened to USGI Specifications
Gas Key Grade 8 Hardened Fasteners
Gas Key Staked Per Mil-Spec. Nice deep pings that engage the screw firmly.
Tool Steel Extractor
Extractor Spring
Black Extractor Insert
Mil-Spec O-Ring

the chart:
https://spreadsheets.google.com/spreadsheet/pub?hl=en_US&hl=en_US&key=0AqmgMm61Ok7WdExwaG16OENzOEZ1akp2a3Y2NjMxTEE&single=true&gid=2&output=html

As far as failures, i have seen extractors break and the occasional bolt. I know gas keys come lose, but i have not witnessed it.
 
Failure of the carrier itself is unheard of. It only happens when the whole rifle kabooms due to a blocked barrel or faulty ammo.

I'm pretty sure what you are reading about is failure of bolts, which is common. A standard AR15 bolt is a wear item that eventually fails. When it fails depends on its quality, your usage, and the gas system length. A poor bolt in a 16" carbine with carbine gas run hard might fail in 1000 rounds. A quality bolt in a 20" rifle with rifle gas might last 15-20,000 rounds. The top makers make better bolts, plain and simple, and if you are going to be hard on the gun or just need top reliability, it's a cheap ($60-80) upgrade.

The other issue is that a few companies have had defective batches of bolts, with the most well-known being Del-Ton around 2008/09. Those could fail very quickly, but it was due to an actual defect (wrong heat treat) and not just typical quality differences.
 
The higher priced BCG's are MPI and HPT tested individually. Some of the lower end ones are batch tested. The chances of getting a bad BCG in a batch is there but rare.

The full auto ones by companies like BCM, Spikes, LMT, DD are all MPI/HPT tested, and are heavier. IMHO they are a great addition for the money to an AR and you can throw the old one in the bag for a back up.
I have seen a few BCG's roll the lugs off after some pretty hard use. Maybe 5 in 20 years.

Most of the problems from BCG's are from the gas key/hardware improperly installed and staked.
 
Thanks, I own three low-mileage AR's, two DelTon carbine uppers on DPMS A2 lowers (carbines) and a Bushmaster A3 HBar. I have had the gas keys properly staked and have upgraded all three bolts with PSA bolts marked "MP". For the amount of shooting I do I figured that would suffice. Then I started reading comments about bolt carriers failing and decided to get some authoritative advice on that one. I couldn't picture a part that strong in this particular platform coming apart or cracking.

JayPee
 
No, I'm aware of the bolt failures, which is why I upgraded my bolts. These comments were definitely in reference to the bolt carrier. I can't recall exactly which forum(s) I saw them on. At any rate they impressed me enough to come here and ask for some guidance and I thank you all for the help.
 
Very difficult to determine with so many AR15 supplier's, I have a 2011 Stag Model 3 in looking at past pictures on the internet it states poor staking of the Stag guns however my 2011 model does not show that rather has quality work. I think with our global economy and craftsman's moving from one company to another it's difficult to assess, the charts posted in this thread are a start however again it changes on a monthly basis.

For me the Stag fills my need occasional use targets, doubt I will ever put 10K rounds though it however it does have a life time warranty.;)

To answer question if properly cared for doubt anyone will see a bolt failure.
 
I just did some quick searches and the only Bolt Carrier failures I could find where cases where the gas key was not properly staked and came loose. While this can indeed be a problem with some manufactures it is an easily remedied problem. Is this what you were referring to or something else? Can you provide some links?
 
No, I'm aware of the bolt failures, which is why I upgraded my bolts. These comments were definitely in reference to the bolt carrier.
Click to expand...

The comments you read were most likely from people who don't differentiate between the bolt, the carrier, and the bolt carrier group. As you can see there are such comments in this thread as well!
 
Someone claiming quality in carriers results in failure is probably talking about a side effect of improperly staked keys. Its a very general statement. too much so to be very useful.
 
OK gents. I think I can go to the range without fear of my bolt carriers coming apart now. I think Z-Michigan's comments are spot on and prolly account for the need I felt to ask some questions. That is, folks who don't distinguish between the bolt carrier and the bolt carrier group. Thank you all very much for the kind assistance. I've been away from AR's for five years due to ill health and just recently got back into them only to find a very different landscape than the one I left five years ago. I've been researching my head off and asking lots of questions. Sorry for the bother.

JayPee
 
If you search M4carbine and ar15.com you will find more info. I do recall a thread and pics of a cracked bolt. No idea of the make.
 
Bolts break all the time. Even in high end rifles if you don't eventually change them. Of course we're talking about 10,000 rounds +.

Never seen a carrier fail. But I have seen weird machineing that couldn't be a good thing. Usually the extractor, bolt, extractor spring fail. Not usually the carrier.

But I like to just order a complete bolt carrier group from BCM and be done with the the whole assembly. $130ish last time I checked. Not an expensive item.
 
I should have made myself more clear that I was talking only about the bolt carrier failing during normal usage with milspec or equivalent 5.56mm ammunition. Those photographs depict a catastrophic failure of the entire bolt carrier group caused by an overloaded .204 cartridge, with no indication that the brand of equipment played a role in the failure. Here's a quotation from post #11 of the referenced link:

"Thanks for the photos. Looks like a typical case head structural failure from overpressure, followed by hot plasma tunneling back into the bolt through the extractor channel and exploding, bolt, bolt carrier, and upper housing from the inside out."

JP
 
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LMT, Daniel Defense, CMT and Bravo have good ones. Palmetto State Armory has 2, one milspec, one not, get the Premium.
Click to expand...

Per a discussion with the guy behind the counter at their store in Columbia, SC, the "Premium" and "non-Premium" BCGs sold by Palmetto State Armory are identical - one just has not been MPI/HPT tested. He had never heard of a non-tested, non-Premium PSA BCG failing. That said, the price difference for a little more peace of mind is only $10.
 
Fishbed77 said:
Per a discussion with the guy behind the counter at their store in Columbia, SC, the "Premium" and "non-Premium" BCGs sold by Palmetto State Armory are identical - one just has not been MPI/HPT tested. He had never heard of a non-tested, non-Premium PSA BCG failing. That said, the price difference for a little more peace of mind is only $10.
Click to expand...

Exactly right - the premium/non premium PSA carriers are exactly the same, and as you say the only difference is between the bolt testing, one being MPI/HPT tested, the other not.

I picked up a non premium BCG when they were on sale and its been great.

As an aside, after extensive research I am finding that these days it seems that the MPI/HPT testing is becoming somewhat redundant - can't remember where I saw it, could have been m4carbine, but it seems that bolts never seem to fail the test these days. That being the case, I'd personally sooner save some money and have one that has not been stressed by an overpressure round. I always carry a spare bolt regardless of whether the one in use is HP/MP tested or not.
 
I should have made myself more clear that I was talking only about the bolt carrier failing during normal usage

which some of us seem to have completely missed.

Apparently "bolt" and "carrier" aren't part of some people's comprehension in reading.

While there appears to be a lot of agreement that milspec bolts have certain features and testing that ensure they meet a contractual standard, those who use batch tested 9310 alloy or Crane SOPMOD bolts aren't too worried about meeting that minimal standard. If anything, the D-ring extractor mod is specific to service carbines because of their early timing and use of milspec ammo. Sticking cases aren't as much problem in midlength gas semi autos.

And they can use the same carrier, no worries at all about them in carbines.
 
The big issue is low-quality bolts and barrels. Barrels and bolts from many manufacturers are not high-pressure-tested and magnetic-particle-inspected, incorrect steels are used, manufacturing processes are not in spec, etc. It is very unlikely that you'll bust a bolt carrier in your rifle. A bolt is much more likely to break in service as you push a higher round count and run the weapon harder.

For a replacement bolt, I'd advise a bolt from a reputable manufacturer which is confirmed to HPT/MPI/shot peened, etc. The best way to get this is when your current bolt is showing appropriate wear or it fails you, you buy a BCM bolt and check it's compatibility with your barrel's level of wear via a no go gauge from Brownell's.

Barrels from Daniel Defense and BCM are confirmed mil-spec steel and manufacturing processes, so if your barrel wears out, get a BCM or DD barrel, they aren't much more expensive than a DPMS or Bushy barrel of inferior quality.

I've sorta branched off on a tirade there, but on the bolt carrier: If it's from a decent mfg'er, it should be fine, just make sure the key is staked. Eventually, your BCG will wear out. When it does, get a good one from DD, BCM, etc.
 
These comments were definitely in reference to the bolt carrier. I can't recall exactly which forum(s) I saw them on.
Click to expand...

as was stated repeatedly, this question was about the carriers, NOT THE BOLTS

to the OP, when you remember which forum you found the highly unlikely reports of carrier failure, send me a PM and i'll reopen the thread
 
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