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Posted: 7/20/2013 6:31:22 AM EDT
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Recently finished 1st complete build and having some minor issues picking round from mag to chamber. I was wondering if not enough gas pressure to bring the bolt all the way back. What is a little odd is that it mostly happens with some new pmag 20 round mags just purchased. Some of the older mags no problem, Lancer. If you look at the gas block where the tube goes in there is quite a bit of soot on the tube and barrel, is this normal? The block seems to be aligned properly when looking at the ring around the hole in barrel. Little new at this so forgive me for poor explanation.
20" BCM barrel BCM gas block BCM rifle length gas tube BCM bcg Marc |
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Put one round in the magazine and load the magazine into the rifle. Chamber that one round, shoot, and see if the bolt locks back on the now empty magazine. If it does, the gas system is fine. (and do this with both the older mags and the new ones) That's really good. I do remember the bolt not staying back a couple of times when I was having issues but don't remember which magazines and I only had a couple of mags with me. If it is not staying open consistently I suppose that would indicate not enough pressure, what next? Thanks Marc |
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What ammo are you using? Could be that as well. I am not the expert but here are some other thoughts: insufficient lube Too heavy buffer / spring losing gas (doesn't seem likely but could be) Rifle length buffer spring and have used quite a bit of rem oil, something better? Variety of ammo Thanks Marc |
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Rifle length buffer spring and have used quite a bit of rem oil, something better? CLP Variety of ammo Always use full power ammo when getting a new rig running. With a "variety of ammo" you have introduced another variable. Does the bolt lock back with one round of full power ammo fired over an empty mag ? Thanks Marc Quoted:
Quoted:
What ammo are you using? Could be that as well. I am not the expert but here are some other thoughts: insufficient lube Too heavy buffer / spring losing gas (doesn't seem likely but could be) Rifle length buffer spring and have used quite a bit of rem oil, something better? CLP Variety of ammo Always use full power ammo when getting a new rig running. With a "variety of ammo" you have introduced another variable. Does the bolt lock back with one round of full power ammo fired over an empty mag ? Thanks Marc |
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I was finally able to get out and try a couple of things. It appears to be an ammo issue. The steel Herters won't barely even ejects the case and the indipendence will cycle rounds but will not hold open the bolt on last round. Tried some better ammo and worked fine. I have not had this issue with other weapons. This is the first rifle length buffer spring i have used. Is it possible the spring is too stiff? If I wanted to shoot some of the cheaper stuff what would my next step be? I pulled the gas block and tube there seems to be no problem. Bolt is lubed and slides freely. I did try with about 8 different mags and same result with all.
Thanks Marc |
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Quoted:
I was finally able to get out and try a couple of things. It appears to be an ammo issue. The steel Herters won't barely even ejects the case and the indipendence will cycle rounds but will not hold open the bolt on last round. Tried some better ammo and worked fine. I have not had this issue with other weapons. This is the first rifle length buffer spring i have used. Is it possible the spring is too stiff? If I wanted to shoot some of the cheaper stuff what would my next step be? I pulled the gas block and tube there seems to be no problem. Bolt is lubed and slides freely. I did try with about 8 different mags and same result with all. Thanks Marc What type of gas block do you have? Are you sure it's lined up perfectly? This same issue happened to a friend of mine. Cheaper steel ammo would not cycle. "Better" ammo would work fine. His gas block was slightly canted and straightening it up solved the problem. |
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I am using a BCM low profile gas block and when taking it off it appears to have a perfect ring around hole in the barrel. Just got back from the range and it seemed much better, it cycled everything but there was an occasion where the bolt did not stay open after last round.
Thanks everyone for the input. Marc |
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