450Bushmaster.net

I have a upper from Bushmaster and this has been the second time that I have had a “tweaked” bolt cam pin....

The first one I had I didn’t think anything of it. I had fired several boxes of ammo through the rifle and I wrote it off to a cheap factory pin.

But this weekend I fired only 5 shots through it and after the 5th the bolt wouldn’t fully seat forward. I split the rifle to again find another bent pin.

What could I have going on here? It shouldn’t be a dirty rifle because I cleaned everything really good prior to these last 5 rounds....

Well, something is seriously out of spec. You didn’t feel anything binding up?

Check inside the upper receiver for marks from the cam pin. Check the bolt and carrier for damage or excessive wear, especially around the cam pin.

Is this a Bushmaster factory upper?

Bmt85 wrote:Well, something is seriously out of spec. You didn’t feel anything binding up?

Check inside the upper receiver for marks from the cam pin. Check the bolt and carrier for damage or excessive wear, especially around the cam pin.

Is this a Bushmaster factory upper?

You didn't say how the pin looked other than bent which is hard to envision. Did it show any unusual wear likes its binding in the raceway that it travels in. How about the bolt lugs? Do they look worn on the mating surfaces that face rearward? I put over 2k rounds through my original bushmaster upper and the cam pin while having some wear where it contacts the raceway, was otherwise good to go. I grease that area of the bolt is MoS2 grease. I'd expect that kind of behavior from reloads that were too hot but not factory rounds. Do the factory rounds pass the Thunk test? If you're unfamiliar with the coined term, it just means will all of them drop freely, all the way into the chamber. I ask out of concern that your chamber might not be cut to spec.

Hoot