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Posted: 2/16/2016 4:09:49 PM EDT
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So I have a quasi-Mk18ish/CQBRish build (Colt 6921 barrel cut to 10.3, gas port sized at .070 per spec, Colt factory auto BCG, H2 buffer, stiff extractor spring with black o-ring insert, 3 gas rings instead of the McFarland ring though). Shooting M855 and M193, it extracts and ejects like you would expect; I can put a bucket on the ground at about 4 oclock maybe 5 or 6 feet away if I'm standing, and every piece of brass will land in it, reliably. However, when I put my suppressor on it - %75 of the time, brass ejects at around 2-2:30, which I would expect now that it's got more gas/blowback...but maybe 1/4 of the time, every now and again, a piece of brass will basically just sort of dribble out of the port. More than a few just fell out of the rifle's port basically, and there was a nice pile of 5 or 6 pieces of brass right next to the rifle after about a mag and a half, and it happened with both M193 and M855. Anyone have any ideas? Being that it's suppressed, any brass marks on the port or anything will be obscured, but I didn't notice anything anyway. The occasional just kind of flop out of the port kind of concerns me. I don't think it's TERRIBLY overgassed, but it's possible the occasional round just puts it just over the threshold? About the only things I haven't done are check/replace the main spring, and/or replace the gas rings on the bolt...and, I guess, replace the ejector spring; it's possible that it's just old or weak... |
| Well, just for shiggles I replaced the ejector spring. Old spring was quite a bit shorter/more compressed than the new one. At the range today, same extraction/ejection without a can, but with a can was night and day. Fairly consistent out at 2-2:30, and not one single piece of brass dribbled out of the port. It all sailed clear with some force. For years I never paid much attention to replacing ejector springs...now I'm rethinking that. |
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Quoted:
Curious how many round's on that bolt and manufacturer if you don't mind? I'm a 10.5" guy so i like to put all i can in my data base...... Colt Bolt...no idea how many rounds. I got it as surplus BCG from CDNN back in the early 2ks; if it helps date it, it had a red extractor insert in it when I got it 
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Quoted:
I would ditch the 3 coil spring and o-ring and get the proper gold extractor springs Colt issues for the guns. Also as you mentioned I would suspect the ejector spring. Extractor springs/gubbins had already been replaced with a BCM extractor spring upgrade kit; it was the first thing I did when I built this thing out, before it ever got close to the range. Extraction isn't an issue, it was just the slighly erratic ejection when suppressed...which seems to be cured now. Wish I had thought of replacing the ejector spring at the time I was replacing the extractor innards. Oh well. |
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Quoted:
Colt Bolt...no idea how many rounds. I got it as surplus BCG from CDNN back in the early 2ks; if it helps date it, it had a red extractor insert in it when I got it Quoted:
Quoted:
Curious how many round's on that bolt and manufacturer if you don't mind? I'm a 10.5" guy so i like to put all i can in my data base...... Colt Bolt...no idea how many rounds. I got it as surplus BCG from CDNN back in the early 2ks; if it helps date it, it had a red extractor insert in it when I got it Cool glad you got it going.... Seriously kicking around cutting my good 6920 and LMT carbine uppers. Since they are just broken in ~ I have beaters that took all the abuse they got to many rnds down them to be worth cutting
I just have no desire for 16 carbine anymore. |
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