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Posted: 2/16/2009 8:33:14 AM EDT
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Hi guys, scanned through the forums a bit, but I couldn't find anyone else with the same problem.
I recently bought a brand new Olympic Arms K3B M4A3 TC, given the election results. I've put several hundred rounds of Federal, HSM and Winchester Varmint through it, and there have been no problems so far, except that the Bolt catch seems to have stopped working. The bolt catch will not hold the bolt open neither after firing the last round, nor when I manually cycle the action. Also, it won't hold the bolt reliably if I pull back the charging handle and manually push in the bolt catch either. On one of my PMAGs, the bolt appears to actually have cut a small notch through the follower, completely disabling the BHO function. It seems to work ok with USGI mags, but maybe that's because I haven't been using them much. Either way, it still doesn't explain why the bolt won't hold open if I manually push in the release lever while the bolt is manually released, having been retracted prior to pressing the catch. I've examined the bolt, bolt carrier and the catch, all show minimal signs of wear. I was planning on taking it to a gunsmith if the problem doesn't resolve itself, just wondering if anyone on here had the same problem. |
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Shotgun the upper open, and insert a empty USGI mag into the mag well. Does this raise the catch catch all the way up with the empty mag follower tension?
If no, the lube the hell out of the bolt catch, and work it by hand until it no longer binds in the receiver slot, then try again. When you can get the empty mag to lift the catch with the lower alone, then lock the upper back down, and try again. Now this time, confirm that the face of the bolt is stopping about 1/4" to 3/8" in front of the back of ejection port, and the catch can rise up in front of the face of the bolt. If the bolt face will not retract that far back when you pull the Charging handle all the way to allow the catch to clear/raise in front of the bolt face, you have a screw up in the receiver extension somewhere. Could be that the recoil spring is too long (carbine springs should be about 10.5"), or just something has found it's way behind the buffer, and the buffer can no longer full stroke and touch the back of the receiver extension like it's supposed to do. |
| Thanks for the help. Followed your instructions, it appears to work fine with USGI mags, not so much with pmags though (used to work fine). I examined the buffer and recoil spring (10.5 looks about right), everything is nice and clean. Both types of mags raise the catch (excluding the worn pmags). Sometimes the bolt closes when I drop the mags out, though. At first I thought there was too much lube on the bolt catch, and the bolt was slipping off, but removing some of the lube didn't help. The catch does seem a bit wobbly when I move it around with my finger, there seems to be too much tolerance with the pin that secures the bolt catch, and the catch itself. Maybe there's some sort of aftermarket catch I can install that will function more reliably? |
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