AR Sponsor
Joined:
Mar 2023
Posts:
1
EE: 0% (0)
ID, USA
Posted: 3/1/2023 10:04:04 PM EDT
|
Is anyone familiar with parts that are most likely to fail on a Bushmaster XM15-E2S. I'd want to have parts on-hand in case they become unbailable. |
| https://www.ar15.com/forums/ar-15/High_round_count_AR_M4_s__over_100_000_rounds__and_how_they_have_handled_on_our_range/118-677135/? |
Can't never could 'til try came along.
|
This is common to all AR-15's, not just your Bushmaster. Cam Pin - if you can feel an edge with your fingernail in the worn shiny area it is time to replace. This is a high stress part. Firing Pin Retainer (aka "cotter pin") - If there is any curviture, replace it. This happens on older exposed firing pin bolt carrier groups when used with notched hammers. The notch drags over the head of the firing pin with every cycle, banging the retainer and bending it. This is why you should use "M16 style" bolt carriers and hammers without notch. Firing Pin - examine the tip looking for chips or wear. Keep a spare on hand. Extractor - remove it from the bolt every 500-1000 rounds and look for wear where it grabs the cartridge case. If any doubt, replace. At the same time put in a new extractor spring, buffer, and pin. Gas Rings - pull the bolt forward in the carrier and stand the BCG on the bolt on a table. The carrier should not fall down to the bolt. If it does, the gas rings need replacement. I would keep TWO sets of 3 rings on hand and replace as needed. The one-piece spiral "McFarland" gas ring seems to last longer. CMMG has a bolt parts kit for about $30 that has all the parts needed in one pkg. Except for the Ejector Pin and Spring in the bolt (and in the CMMG kit) all of the parts above are easily replaceable with very few tools, perhaps a pocket knife to pick the rings out. In more than 30 years of shooting AR's, I've never had a problem with a charging handle, nor any of the fire control group. I've had some worn gas rings, one carrier that would break a gas ring with every trip to the range (fixed by discarding that carrier), cam pins (replaced on two rifles just today), and one worn extractor. I have replaced lots of firing pin retainers in rifles with notched hammers and cutaway bolt carriers. Since installing un-notched hammers and M16 style BCG's on those rifles I have not had to change a single firing pin retainer. |
|
Originally Posted By OTDR: Thats SOTAR nonsense. Originally Posted By Embittered: Never made sense to me. This explains the reason for putting the cam pin consistently in the same orientation. I feel the logic here has some potential validity, yet I have no way to confirm one way or another. https://www.forwardcontrolsdesign.com/SCP-SOTAR-Cam-Pin_p_206.html |
|
Originally Posted By Against-The-Wind: This explains the reason for putting the cam pin consistently in the same orientation. I feel the logic here has some potential validity, yet I have no way to confirm one way or another. https://www.forwardcontrolsdesign.com/SCP-SOTAR-Cam-Pin_p_206.html I don't I think someone posted in another thread awhile back information that made me feel distributing the wear on both sides made more sense. But aside from that I have never had a cam pin failure, paying no attention to direction, in all the years I have owned an AR. I am old and been into guns since the 70's. AR's early 80's. If I was going to mark one it would be so I could rotate it 180 degrees each time I cleaned the BCG. 
|
|
Originally Posted By j3_: I don't I think someone posted in another thread awhile back information that made me feel distributing the wear on both sides made more sense. But aside from that I have never had a cam pin failure, paying no attention to direction, in all the years I have owned an AR. I am old and been into guns since the 70's. AR's early 80's. If I was going to mark one it would be so I could rotate it 180 degrees each time I cleaned the BCG. I've heard others state that they would assume spreading the wear to both sides would be better. The issue is that I believe the cam pin wears to a point and then does not get much deeper. So if you keep this wear on one side of the pin only, then the pin will always have a tighter fit into the bolt, opposed to a sloppier fit when both sides of the cam pin are significantly worn. And it makes perfect sense that a looser fitting cam pin if not ideal for the bolt. |
AR Sponsor