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LAKings22
10-10-2012, 10:19 PM
Over the weekend my brother in law was at the range and after aprox 150 rounds the bolt on his AR broke in half. What can cause that to happen?


173626
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FCOD
10-10-2012, 10:21 PM
Wowzers!

NewbieDave
10-10-2012, 10:25 PM
http://ar15barrels.com/tech/broken-bolt.jpg

http://i244.photobucket.com/albums/gg34/stealthyblagga/BrokenBolt.jpg

It happens more common then most people think. Improper heat treatment can cause stress at that point. Basic metallurgy stuff. What brand is it?

Usually name brand bolts that has been properly MPI tested doesn't happen as much if at all... the saying "You get what you pay for..." is very true when comes to bolts. That's why LMT, DD, etc charges an arm and leg for good bolts. Not saying it can't happen to those bolt, but bad batch are usually caught during the MPI testing.

tiechshlime
10-10-2012, 10:26 PM
That is where they crack and then get replaced. Usually after alot higher round count then 150.

LAKings22
10-10-2012, 10:27 PM
http://ar15barrels.com/tech/broken-bolt.jpg

http://i244.photobucket.com/albums/gg34/stealthyblagga/BrokenBolt.jpg

It happens more common then most people think. Improper heat treatment can cause stress at that point. Basic metallurgy stuff. What brand is it? Usually name brand bolts that has been properly MPI tested doesn't happen as much if at all...

I'm not sure what brand it is. Anything good you can recommend?

tiechshlime
10-10-2012, 10:30 PM
bcm

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

NewbieDave
10-10-2012, 10:38 PM
Good as in a brand? As stated above, BCM is good... Rainier Arms, LMT, DD, Spikes... all good MPI tested bolts. And they stand behind their products.

Was it off a complete rifle or parts kit?

hermosabeach
10-10-2012, 10:54 PM
Yes- curious as well who made the rifle and who made the bolt

If I had to replace a bolt I would look for one that is Nickle Boron coated...

Several company sell complete bolts that are coated and it is easy to keep carbon off of them.

hermosabeach
10-10-2012, 11:00 PM
Here are a few makes- I doubt my search found the best prices.
Look for a mil spec bolt with the gas carrier staked.

The biggest issue with the AR and reliability is carbon buildup on the bolt

If not NB- go mil spec from one of the big manufacturers-
LMT
Colt
Etc...

Wmd
http://www.brownells.com/.aspx/pid=54072/Product/AR-15-NICKEL-BORON-BOLT-CARRIER-GROUPS

http://www.marksarmory.com/Black_Rain_Ordnance_BRO_Nickel_Boron_BCG_p/bronickbcg.htm

Spikes tactical
http://www.joeboboutfitters.com/Spike_s_Tactical_Nickel_Boron_M16_BCG_223_5_56_p/sp-st5bg03.htm

LAKings22
10-11-2012, 12:00 AM
It's a parts kit, but he didn't build it. He purchased it complete so he doesn't know what brand the bolt is. I'm sure it's a cheap brand if it broke that fast.

The BC is nickel but he doesn't know who makes it.

LAKings22
10-11-2012, 12:16 AM
Here are a few makes- I doubt my search found the best prices.
Look for a mil spec bolt with the gas carrier staked.

The biggest issue with the AR and reliability is carbon buildup on the bolt

If not NB- go mil spec from one of the big manufacturers-
LMT
Colt
Etc...

Wmd
http://www.brownells.com/.aspx/pid=54072/Product/AR-15-NICKEL-BORON-BOLT-CARRIER-GROUPS

http://www.marksarmory.com/Black_Rain_Ordnance_BRO_Nickel_Boron_BCG_p/bronickbcg.htm

Spikes tactical
http://www.joeboboutfitters.com/Spike_s_Tactical_Nickel_Boron_M16_BCG_223_5_56_p/sp-st5bg03.htm

Thanks for the link. We're going to take it back to the guy who build it and have him change it out. I'll make sure it's something good.

When I purchased my first AR, I had never even shot one before and I didn't know anything about it. Now after seeing this on his rifle, I'm 100% convinced its better to build your own then buying it complete and risking the shop from cutting corners on parts.

klewan
10-11-2012, 9:07 AM
That would be the place for it to break; smallest cross section, so the weakest. This MPI is also know as magnafluxing. Put the ferrous part in a magnetic field and wash it with a liquid that has tiny iron dust and a fluorescent particle mixed in. Examine the part under a black light, any cracks will glow.

I worked at a Ford plant back in the 70s, I was running a machine that did the final machining on full size car front spindles. They had 3 women inspecting them under a black light for cracks. Each woman was responsible for a certain part of the spindle and had a paint marker to make that the part had been inspected and passed.

Munny$hot
10-11-2012, 10:24 AM
The heert of the ar is the barrel & bolt followed by the fcg.

WETP
10-11-2012, 11:15 AM
Bolt failures can happen. Yes buy good quality equipment, personally, I run LMT and BCM on my DI equipment. But more important IMO is to run your quality checks often. Chances are that bolt had an hair fracture before it failed.

supersonic
10-11-2012, 11:20 AM
If you can find one in stock, Genuine Colt AR-15 bolts are shot-peened, proof-tested, and MPI tested. The bolt they send to you will have 2 characteristics:

1. Near where the body of the bolt meets the lugs, there will be a stamp that looks like this: CMP or sometimes CMP HPT. Those acronyms stand for "Colt, Magnetic Particle Tested" and "Colt, Magnetic Particle Tested / High-Pressure Tested". (I'm not 100% sure if the "double stamped" one is in that exact order, but you get the idea).

2. The Bolt manufactured by Colt would still be in the rifle working as it should.


*Note: any bolt can have this happen with a highly-over pressurized load and it usually happens much further down the road (say, in the hundreds of thousands of rounds when a defective round is touched off). But bolts such as Colt/LMT/BCM, etc. are each tested multiple times with "proof loads" which are rated at/or above70,000 psi. after they are manufactured and are going into the rifle for the first time at the factory. The barrels on these same rifles have those same tests done to them beforehand as well (since the proof load needs to be shot out of a rifle - almost always the one that same bolt will be matched with - as the bolt takes the #1 hardest hit when firing, and the barrel is the only other part that takes that direct "stress hit" (though not as direct and hard a slam) from proof (and later standard) cartridge detonation.

EDIT: the "CMP" is actually usually stamped as "MPC"

m03
10-11-2012, 11:53 AM
If you can find one in stock, Genuine Colt AR-15 bolts are shot-peened, proof-tested, and MPI tested. The bolt they send to you will have 2 characteristics:

1. Near where the body of the bolt meets the lugs, there will be a stamp that looks like this: CMP or sometimes CMP HPT. Those acronyms stand for "Colt, Magnetic Particle Tested" and "Colt, Magnetic Particle Tested / High-Pressure Tested". (I'm not 100% sure if the "double stamped" one is in that exact order, but you get the idea).

2. The Bolt manufactured by Colt would still be in the rifle working as it should.


*Note: any bolt can have this happen with a highly-over pressurized load and it usually happens much further down the road (say, in the hundreds of thousands of rounds when a defective round is touched off). But bolts such as Colt/LMT/BCM, etc. are each tested multiple times with "proof loads" which are rated at/or above70,000 psi. after they are manufactured and are going into the rifle for the first time at the factory. The barrels on these same rifles have those same tests done to them beforehand as well (since the proof load needs to be shot out of a rifle - almost always the one that same bolt will be matched with - as the bolt takes the #1 hardest hit when firing, and the barrel is the only other part that takes that direct "stress hit" (though not as direct and hard a slam) from proof (and later standard) cartridge detonation.

No way. Everyone knows that you only buy Colt for the brand name.

:) :) :)

supersonic
10-11-2012, 12:23 PM
No way. Everyone knows that you only buy Colt for the brand name.

:) :) :)

You are 100% correct.:thumbsup::p

ar15barrels
10-11-2012, 12:40 PM
About 8 or 9 years ago, Bushmaster had a bad batch of bolts.
They were heat treated too hard, or perhaps not annealed correctly.
The picture of the one on the wood bench above is a picture of mine from one of those bushmaster bolts.

rojocorsa
10-11-2012, 1:07 PM
Here are a few makes- I doubt my search found the best prices.
Look for a mil spec bolt with the gas carrier staked.

The biggest issue with the AR and reliability is carbon buildup on the bolt

If not NB- go mil spec from one of the big manufacturers-
LMT
Colt
Etc...

Wmd
http://www.brownells.com/.aspx/pid=54072/Product/AR-15-NICKEL-BORON-BOLT-CARRIER-GROUPS

http://www.marksarmory.com/Black_Rain_Ordnance_BRO_Nickel_Boron_BCG_p/bronickbcg.htm

Spikes tactical
http://www.joeboboutfitters.com/Spike_s_Tactical_Nickel_Boron_M16_BCG_223_5_56_p/sp-st5bg03.htm

I thought that the biggest AR reliability issue was bad action springs, bad extractor springs, and bad mags.

At least that's what Mike Pannone said.
http://www.defensereview.com/m4m4a1-carbine-reliability-issues-why-they-occur-and-why-theyre-our-fault/

Sunday
10-11-2012, 1:15 PM
The problem is low quality parts and not enough lube. Keep it lubed and buh high quality parts and the AR will last and last. Guns are machines and machines do wear and break. Stay with the highest quality parts, Bravo company is a known source of high quality parts. Been messing with AR 15s since the early 70s and the ARs [Back then it was only Colt] with quality parts run and run.

Sunday
10-11-2012, 1:17 PM
You are 100% correct.:thumbsup::p
Can't go wrong with Colts. I like BCM for the Value. Colt quality, Bushmaster prices.

supersonic
10-11-2012, 2:12 PM
About 8 or 9 years ago, Bushmaster had a bad batch of bolts.
They were heat treated too hard, or perhaps not annealed correctly.
The picture of the one on the wood bench above is a picture of mine from one of those bushmaster bolts.

Wow! What's it been ..... about 2 years??? I never thought I'd see you back here. Well, it takes a real man to do what you had to do in order to lift that lifetime ban. In any case, welcome back, Randall. Frankly, I miss the extremely informative info you posted on here. Now we can look forward to more. BTW, how long have you been back?

JoeBobOutfitters.com
10-11-2012, 2:39 PM
Sorry to hear about the bolt blowup. It can happen, but obviously the higher end bolts "should" be less prone to failure.

We have some Kies bolts in stock that are both MPI tested & Carpenter 158 steel:

Kies AR15 Nickel Boron Bolt (http://www.joeboboutfitters.com/Kies_Nickel_Boron_AR15_Bolt_Carrier_Group_BOLT_ONL _p/kies-kbn.htm)-$98.95

Kies AR15 Bolt (http://www.joeboboutfitters.com/Kies_223_5_56_AR_15_BOLT_No_carrier_p/kies-223-bolt.htm)-$54.95

ar15barrels
10-11-2012, 2:43 PM
Wow! What's it been ..... about 2 years???
I never thought I'd see you back here.
Well, it takes a real man to do what you had to do in order to lift that lifetime ban.
In any case, welcome back, Randall.
Frankly, I miss the extremely informative info you posted on here. Now we can look forward to more.
BTW, how long have you been back?

All your questions are already answered here:

http://www.calguns.net/calgunforum/showthread.php?t=620369

Mail Clerk
10-11-2012, 8:03 PM
I'm not sure what brand it is. Anything good you can recommend?

LAKings22,

Most likely it was due to improper heat treating and so because it is considered a part they all can break. Just don't worry about it....get another that might be better. How about a hard chrone or a nickle boron one???

Mail Clerk

LAKings22
10-12-2012, 12:50 AM
LAKings22,

Most likely it was due to improper heat treating and so because it is considered a part they all can break. Just don't worry about it....get another that might be better. How about a hard chrone or a nickle boron one???

Mail Clerk

Well my brother in law is going to take it back to the guy this Saturday and work something out with him. I gave him all the information you guys provided and ill put out an update of what happened.

Mail Clerk
10-12-2012, 7:58 AM
Well my brother in law is going to take it back to the guy this Saturday and work something out with him. I gave him all the information you guys provided and ill put out an update of what happened.

LAKings22,

I'm sure the store will replace it since only 150 rounds were shot from it. Just in case be prepared to buy another as the store manage might make a biig deal out of it. I've had some of those.

In case he won't replace it just head out to Riflegear and get a nice Spikes nickle boron complete bolt. Since your a local boy the distance isn't too far for you.

Personally I've been buying AR's and bolts from Model 1 sales and so far never had any breakages at all but then again I don't shoot thousands of rounds per year like some people on this forum do. I'm glad AR15 Barrells.com is back.

Mail Clerk

Sunday
10-12-2012, 2:24 PM
Over the weekend my brother in law was at the range and after aprox 150 rounds the bolt on his AR broke in half. What can cause that to happen?


173626
173627173629173630
What is the total round count?
Who was the manufacture of the gun/parts? parts aren't parts.

LAKings22
10-12-2012, 2:40 PM
What is the total round count?
Who was the manufacture of the gun/parts? parts aren't parts.

He was at around 120-130 rounds before it broke that day. Total round count is under 500. His taken it to the range total 3x and cleaned it after every time.

In all fairness to the shop, he was having problems with couple of company's he was ordering parts from around that time. So I can't pin point what parts ended up in that rifle and since it wasn't my personal rifle I never really asked him.

Mail Clerk
10-13-2012, 6:24 AM
LAKings22,

Again most like the shop will replace it for you but if not just head to any store of your choice and get another. Since the bolt carrier appears to be in one piece all you need is the bolt and that can be up-graded.

Good luck,

Mail Clerk

Knife Edge
10-13-2012, 6:50 AM
Like I have said before, no firearm is proven until it has had 800 to 1,500 rounds down range (except maybe bolt guns). While I have never had a failure on this level, this is also the reason people carry spare bolts in their pistol grips.