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Posted: 9/7/2009 12:12:23 PM EDT
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So I FINALLY shot my MEGA build today. MEGA upper and lower, Noveske 18" SPR bbl.
On slow fire, the bolt locks back when the mag is empty. On rapid fire, it doesn't. This started about round 80, after I'd finished sighting in my scope, and began some rapid fire (i.e. fast controlled fire, maybe 1.5 shots per second). Using Magpul 20 round mags that work fine in other rifles. XM193 ammo, same lot has worked fine in other rifles. It locks back fine using the charging handle. I ran out of ammo before I could do much more testing (like putting the upper on another lower, trying different ammo, etc.) Thought: Is it possible that this being a new barrel that somehow the gas port got clogged and is just barely short stroking? There's no problem with extraction and ejection. Any ideas? |
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99.9% sure that had you pulled the B/C and re-lubed it with CLP (read a healthy squirt of such inside and out, then the B/C back in the upper worked a few time to allow the CLP to migrate), the problem would have gone away (read being a break in problem with the new/rough inner surfaces fouled out from self polishing and powder fouling causing too much drag as the rifle was cycling).
In slow fire mode, the little amount of lube in the rifle has time to do a tad self cleaning to allow the rig to full stroke correctly, while in rapids, the little amount of remaining lube did not have time to so the same, and the rifle was fouling out faster than it could handle. With fresh lube, this would not have been a problem. Also, in a few hundred rounds, the amount of lube needed will much less since the parts will have mated by then (parkerizing against anodizing). Also, might want to check the gas block as well. If the barrel is heated up high enough/fast enough with a loose block, you going to get more of a gas leak the hotter the barrel gets (same as the gas key as well). |
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Quoted:
99.9% sure that had you pulled the B/C and re-lubed it with CLP (read a healthy squirt of such inside and out, then the B/C back in the upper worked a few time to allow the CLP to migrate), the problem would have gone away (read being a break in problem with the new/rough inner surfaces fouled out from self polishing and powder fouling causing too much drag as the rifle was cycling). In slow fire mode, the little amount of lube in the rifle has time to do a tad self cleaning to allow the rig to full stroke correctly, while in rapids, the little amount of remaining lube did not have time to so the same, and the rifle was fouling out faster than it could handle. With fresh lube, this would not have been a problem. Also, in a few hundred rounds, the amount of lube needed will much less since the parts will have mated by then (parkerizing against anodizing). Also, might want to check the gas block as well. If the barrel is heated up high enough/fast enough with a loose block, you going to get more of a gas leak the hotter the barrel gets (same as the gas key as well). Good info. I gave it a normal lubing, which for me is not too wet. I did notice that's the action isn't as slick as, say, a rifle with a couple thousand down the tube. I'll be sure and squirt some CLP on the BCG during my next range trip. |
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