* UPDATE *

I got in contact with Dave @ DPMS customer service.  He had me send in the bolt for inspection and in a few weeks I had a new bolt show up in my mailbox.  It's nice to still receive customer service from a company.  All in all everything went pretty smoothly, thanks again for everyone’s input.

--NeedAclip




I just got back from the hills where my "16 carbine just had the bolt crack in half.  My buddy was shooting and all of a sudden he calls me over and the bolt is all jammed up against the carrier and the side of the receiver.  I managed to push the bolt back in place so I could disassemble the rifle and check for damage.  I checked the lugs on the bolt and the receiver with neither of them showing any shearing or abnormal wear.  The carrier also looks as if nothing happened.  Should I just buy a new stripped bolt and put her back together or could there be an underlying factor that caused the bolt to crack in half?  If anyone is curious it was a DPMS bolt and carrier.

Thanks,
NeedAClip

Your best bet is contact DPMS and let them look at the bolt.

I agree, if it is a defective part they will replace it free.
Also may indicate a QC problem that needs to be addressed.

It could be a headspace problem and not the bolt itself. If you are going to get the manufacturer involved, then insist on send the upper back and have them provide a new - properly head speced bolt.

It's nice to have a field guage to check your headspace every 1000 rounds or so. I have had one carbine go 8,000 rounds with no problems, but in another one after 4,000 rounds the headspace indicated a new bolt.

When ever you need to put a new bolt into any of your ARs, the headspace needs to be checked or you might cracked the bolt in just a few hundred rounds.

I learned from experience.

joe

 If it broke at the cam pin hole, then just replace it.  They do break from time to time, that's why you are supposed to check them for cracks per the TM.

Replace it with a Colt, military contract, bolt head.  The commercial makers leave the hole with sharp edges, and that's why the things break.  Colt, and the military contractors, as part of military specs, have to micro polish the part which minimizes the risk of this happening.  The only military spec bolts I've ever heard of breaking were very old pieces, with mucho full auto use.

The current commercial stuff is made out of good material. It just isn't finished off properly, 'cause they're trying to save a buck.  I'd rather have a used military surplus piece from Colt, than any of the new aftermarket bolts.

Oh yeah--that's right. I do have used military Colt bolts in all my ARs[:D]

I recently had a bolt crack as well, actually it broke right off and was still locked in the barrel extension.

I ordered a new bolt and have been toying with a thouoght, could the old one be migged or tigged and put back in service, at least for range work? It would seem that as long as the heat treatment of the face and lugs was not compromised that it should work, has anyone tried this?

Throw the old bolt away.  The reason that it snapped was that it was heat treated wrong, making the metal too brittle.  

By welding up one spot, it will just snap next to the weld the next time.

I've seen two law enforcement DPMS full auto guns break the bolts in half at the cam pin.  We might never know, but I suspect a heat treating problem as well.  DPMS promptly replaced them, with no questions asked.

I sent the bolt in to Dave at DPMS.  He's supposed to look it over and let me know what the deal is.  The guys at DPMS seem really customer oriented, so I don't think I have any thing to worry about.

-NeedAclip

Hopefully..
They don't replace out of spec lower parts kits, they basically tell you to piss up a rope.

I would add this to the broken bolt mess.

"shot peening"
"8620"

Now Google them. [:D]


[b]HINT[/b]
"milspec"
not "milspec"

During my years of reading posts in these forums, nearly every reported case of a broken bolt involves parts from DPMS.  It seems that DPMS should go have a serious meeting with their vendor after having a reputable materials lab analyze the failed parts.  Seems they have a real QC problem with their bolts.

Could someone enlighten me then on why the M4 has so many problems with bolt cracking in Afghanistan?  I would assume that the M4 used by the military is not made by DPMS, so I'm wondering what other possible causes there may be.

Troy, what you say here makes alot of sense.  My DPMS broke the bolt at the cam pin as well.  Mine is free floated with a superbull barrel.  It's not weight of crap hanging off the barrel but the barrel itself weighs about 14 tons.  I can see where that might be a problem.  In my case DPMS did replace the bolt free of charge as well.  I'm ordering 2 spare bolts soon, any place in particular I should order to get milspec new bolts?

Not sure who Troy recommends but I buy Colt [url=http://www.sawlesales.com]here[/url]. Tell 'em ARF sent ya.