AR-15 bolt carrier assembly

[tigercole21]

I just recently got a dpms sportical from my uncle that has been fairly used. The bolt looks pretty worn down. How do I know when to replace the bolt?

 

[TEAM101]

Does it run? If so, it should be fine. Most rifles will run for thousands and thousands of rounds before needing parts replacement. You can check your gas rings by pulling the bolt forward until it stops, then standing the bolt carrier assembly on the end of the bolt. If the bolt slides back into the carrier under the weight of the carrier, first check to make sure the gaps in the gas rings are not lined up with each other (if they are, spin them so they are staggered and repeat the test) if they are not, you should replace the gas rings.

 

[rcmodel]

I'd carefully check the bolt locking lugs for cracks using a magnifying glass.

If you find no cracked lugs, and the cam pin hole is not all wallowed out oval, it is good to go.

I second the gas ring check & replacement if it fails the test outlined by Team101.

rc

 

[walking arsenal]

It's a "plug and play" part. You just pull it out and slap a new one in. A new bolt is about $50. If you question it, you might as well buy a new one and keep the old one as a spare.

Learn to strip down your rifle for cleaning too. I recommend Pat Sweeney's book of the AR-15 1st edition for instructions on that. It has other info in it too that is a fun read for AR owners.

 

[OPtac5]

When I inspect the bolt of my M4 I check for unusual wear marks, concentrated pitting on the bolt face, burrs, and cracks. Some pitting is okay, but if there is any concentration, the bolt should be replaced. I also check the rings by placing the bolt in the carrier without the cam pin and hold it with the bolt side down. The bolt should not fall out. If it does, the rings should be replaced. The rings themselves should be free of bends and spurs.

 

[taliv]

Does it run? If so, it should be fine. Most rifles will run for thousands and thousands of rounds before needing parts replacement. You can check your gas rings by pulling the bolt forward until it stops, then standing the bolt carrier assembly on the end of the bolt. If the bolt slides back into the carrier under the weight of the carrier, first check to make sure the gaps in the gas rings are not lined up with each other (if they are, spin them so they are staggered and repeat the test) if they are not, you should replace the gas rings.

if it is a plinker/training gun, i would run it until it breaks, even if it starts to have some cracks. (of course, i keep several spare bolts around...)

if it were a duty gun or match gun etc, I would replace the bolt itself around 5000 rounds. you might be able to see cracks developing and you might not, but odds are, they are there. there are two places bolts typically crack: 1) in half, around the cam pin hole, 2) the lugs will sheer off. usually the first lug to go is opposite the extractor

you may or may not need to replace other parts in the bolt assembly earlier:
the extractor is a wear part, as are the gas rings (you do not need to mis-align the gas rings when you perform the standard test described in post 2), and the springs and insert for extractor and ejector

 

[mastiffhound]

I hate to reopen this old thread but I need help. I have a crack that is 3 quarters of a circle around and the same size of the primer. First is the rifle, Ruger SR-556. Next, 200 rounds have been through this rifle. Next, no I have not shot reloads through this rifle. Just Pmc bronze and fiochi 69 grain sierra mk.

I clean the rifle after every outing, I'm anal retentive that way. It is a perfect circle the size of a primer. No, there are no blown primers I checked. Can someone please give me some answers. I have little expierience with this platform. I would like to know if anyone else has had these problems with any other rifle or this one?

 

[Mad Machinist]

It is highly unlikely that a crack would propogate in a perfect circle......if it is in fact cracked....call Ruger.....they'll be VERY interested and eager to solve your problem. I would say slap a new bolt in....but I'm not extremely famaliar with an SR556 and unsure if a milspec bolt will fit or headspace correctly......but if you have a circular crack in the bolt face it is probably due to the firing pin hole being machined incorrectly. Take a sewing needle and run the tip across the suspected crack....if it the problem I described above.....then the needle point will hang most likely......DEFINITELY call Ruger and report the problem.

I'f you are near Macon Ga stop by the shop...I'll be happy to inspect for you to include magnaflux magnetic particle inspection.....and measure to see if a standard bolt will work.....as well as check headspace with a new bolt.