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Posted: 3/26/2009 5:22:05 PM EDT
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Hey folks, new to the forum but not to the weapon system. After searching the threads, I have a question regarding the expected friction for a older BCG in a new Upper receiver. I have a Bushmaster XM15-E2S with about 2000 rounds through it. Today I installed a new A3 flat top upper from Stag. I noticed that (and I know this is hard to describe in words) there is more friction with the BCG sliding forward and back in the new Stag upper than in my old Bushmaster upper. Is this expected? I would imagine so as the original setup was a matched set and it has at least 2000 cycles so I'm sure a nice groove has been worn in. But, I want to know how much is too much friction. I've tried the bolt w/out the carrier and its the same, and I'm sure its not friction from the gas key contacting the gas tube - I feel friction before that contact and the gas tube is nice and centered in the carrier. The friction is consistent the entire way, so it doesn't feel like a bur or a crimp in the metal - it just feels snug.
I tested the bushmaster with the BCG and when I tip the assembly up, the BCG just falls right out. When I tip the Stag assembly up the BCG stays put, but with just a little tug with my finger, it starts moving and keeps the same amount of resistance until it's out. I've inspected the inside of the new upper and I can see where the metal is being polished, so I can ID the friction point, so should I just let it go and put some rounds down range and see if it loosens up? Again, its not really TIGHT per say, just SNUG. It doesn't fall out on its own, but I can easily push it in and pull it out with a single finger. Thanks! |
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The bind is the sides of the key against the upper track.
If CLP lubing the key/upper helps, it may be enough to allow the key to mate to the upper track. If not, and run into short stroking problem, then you may need to lap the sides of the key to prevent binding. |
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