AR-15 buffer. Metal erosion?

[JonB]

Well ya'll got me curious so I took a look at mine as well. I have a 'ring' forming on the buffer, but it is different. It looks like a burr on the BC, but upon closer inspection, the little notch on the bottom of the BC is actually higher on one side. Just slightly, but I can feel it by running my finger across the notch and can definitely feel an edge.

So, what's the fix for it? Easy as filing it smooth, or a new BC, or one of the buffer pads, or ignore it?

 

[kcmike]

Hey coloradokevin,
good suggestions so far. If it is not the buffer retaining pin you may want to check the back of your carrier for a burr. I have seen a small burr cause similar damage to a buffer,
best
Mike

ETA: JonB beat me to it.
JonB, just use a little fine grit sandpaper and smooth it out.

 

[AR-15 Rep]

Looks like the problem is all around the BC to Buffer contact. When you assemble the rifle does the BC touch the buffer? it should be touching the buffer pushing it back slightly. If there is a gap then the BC slams against the buffer, it could be just a little bit and then you have a hammering effect between the two.

 

[coloradokevin]

Looks like the problem is all around the BC to Buffer contact. When you assemble the rifle does the BC touch the buffer? it should be touching the buffer pushing it back slightly. If there is a gap then the BC slams against the buffer, it could be just a little bit and then you have a hammering effect between the two.

Okay, so I checked closely tonight while cleaning the Bushmaster from some shooting.

Both the Colt and Bushmaster buffer assemblies appear to be composed of non-ferrous metals (neither will react to a magnet). This satisfies one possibility that someone raised in this thread.

I also checked the situation that AR-15 Rep mentioned... The bolt carriers on both rifles push ever so slightly into the buffer spring when the rifles are assembled. So, they do both have similar contact.

I also looked at the retention detent, and it appears far too short to have made the marks on my Bushmaster's buffer assembly... This mark also appears to match up nearly exactly with the back face of the bolt carrier (so I will assume that the bolt carrier caused the damage to this surface).

In examining the bolt carrier, there are no burrs on the metal, and nothing appears abnormal about this part (smooth and consistent).

So, I'm still sort of at a loss regarding the cause of my rifle's situation! Fortunately the etching appears to be fairly superficial at this point... It isn't deep enough to feel a difference in thickness between the marred surface and the rest of the buffer. Nevertheless, the area where the abrasion occurred does feel rough to the touch.


My guess at this point is that perhaps Bushmaster either:

1) coated their bolt carrier with a more abrasive finish than is used on the Colt rifles

or

2) Used a buffer made out of a softer and less durable metal (though I'm guessing both are some type of aluminum alloy).

 

[RevolvingCylinder]

Well just FYI no M16 or AR maintenance guide shows that to be a place for grease so just keep that in mind. Extra grease and the AR/M16 platform don't go well together.

Maybe not grease but extra oil won't harm a thing. Extra oil and the AR/M16 platform do just fine. It will shed any extra oil it doesn't need with cycling. It was designed as a combat weapon and functions like one. Too little oil on the other hand is not recommended(same could be said for any weapon really). I never use grease on AR15s or M4s or M16s.

I can't see the pics but,
I'd just continue to use the Bushmaster until any actual problems show. If it's just superficial it's just that. If it needs replacing, it's an easy part to replace.

 

[Ridgerunner665]

A few years back I read of some Bushmaster lowers being out of spec. The buffer retaining pin hole is drilled just slightly too far back. This causes the buffer to hit the buffer retaining pin. As it rotates around, it can create that. Also, if it is hitting the buffer retaining pin - that means it is not mating up against the back of the carrier flush and with contact. So when the carrier comes recoiling back - instead of going with the buffer, it first slams into the buffer. Even if it's a few thousandths ...it can make a difference.

There is the problem I believe.