I was cleaning and inspecting a buddies AR today, and noticed these unusual wear “stripes” on the bolt body ridge that contacts the inside of the carrier. I’ve never seen wear like this before on any other bolt. The inside of the carrier looks and feels normal. This rifle only has 200-300 rounds thru it.
Is this anything to be concerned about? What could be causing it to wear unevenly like this?
The ring area was cut slightly when the lugs were cut out, see how they line up?.
Interesting… I guess the real question is why would a manufacturer do that? Perhaps unintentional?
I replied to the same thread you started on " The Other Forum". 
From a machining standpoint it’s a bit easier to manufacture it this way. From a friction perspective it makes sense to reduce the surface area where it rides in the carrier.
Are you suggesting it was machined this way intentionally? I highly doubt it.
But it’d increase the rate of wear (however minimally) since there’s less bearing surface. I can’t imagine COLT breaking the spec on the bolt like this. It looks like some nonsense that LMT would try.
I’ve never seen a bolt like that. I’d ask S.A.W. if this is OK… or try contacting COLT directly.
I was referring to the “slots” in the bearing area. I’m not sure if it was intentional or not.
My brand new LMT bolt has a smooth band all the way around the bolt.
you and scotty must be buddies.
OP- that’s assuredly a fuckup. get ahold of colt or your dealer and get a new one.
See Colt’s response below:
Good Afternoon Mr. ____,
I have forwarded your picture to both the product service manager as well as our resident rifle expert. Both have agreed that your Bolt assembly needs to be replaced. I will send you a FedEx shipping label to bring the Bolt assembly back in so we can replace it for you. Which address would you like it sent to? Thank you for your pictures and your patience in this.
Sincerely,
Kara
The thing that I find to be odd about the wear marks is that they are perfectly in line with the feed ramps. Are we sure it’s a bad bolt and maybe not a problem with the machining of the feed ramps in the upper receiver?
This doesn’t make sense. For one, the feed ramps would line up with the other side of the bolt on the bottom, and two, this part of the bolt never travels for enough forward to contact the feed ramps
Feed ramps??? They are perfectly in line with the lugs…
Who is “scotty”?
He is referring to Scott Ryan in this thread
This is why I buy from tier-1, they may not be perfect, but they usually go above and beyond with CS
I’m sorry, I haven’t slept in two days and my brain isn’t functioning very well… Yes that is what I meant.
Looks like the operator didn’t seat the end mill all the way into the collet during a bit change and the CNC didn’t know any better.
Ah!! His name isn’t really Scott, but yes… I agree with him most of the time.
LMT is the “new bushmaster” in my opinion.