LanceS4803
Well-Known Member
Still no resolution to problem of failing to hold open after last round on empty mag. (Previously it also wouldn't load next round, didn't encounter that today.)
This is 1 of 3 rifles, all identical builds except the problem rifle has a 16" Hanson profile build barrel, while the other two are standard profiles.
Mid length gas, pinned gas blocks and carbine buffer setups, same bolt carriers.
Pulled pin and screws from gas block (non-adjustable) and checked barrel gas port which is free and clear, (gauging pin drops right through into bore) measuring a little over .070, which is spec for that barrel. Gas block lines up perfectly with gas port in barrel. Forced air through gas tube, it exited from around loose gas block. I didn't unpin the gas block from the tube and didn't pull the brake to completely remove block from barrel. Reassembled and forced air through gas tube, and it was exiting barrel.
Gas key tight and staked, no interference with gas tube when installed.
Checked carbine buffer weights, all 3oz. All springs are 11".
Range Testing
Put problem upper on known good lower from other rifle, still failure to hold open. (Problem lower worked fine with known upper.)
Put bolt carrier and charging handle from known upper into problem upper, still failure to hold open. (Problem rifle bolt carrier and handle worked fine in known rifle.)
Put spring and buffer from known good lower into problem rifle, still failure to hold open. (Problem spring and buffer worked fine in known rifle.)
Shooting M855 green tip. (Also tried a couple of different Federal SP loadings.)
Ejection pattern in 3 to 4 o'clock, about 8-10' away.
At this point it is obviously the gas system. I am wondering if I have an internal defect in either the block or the tube causing a slight obstruction. Am considering just ordering new ones.
Can't think of anything I am missing.
This is 1 of 3 rifles, all identical builds except the problem rifle has a 16" Hanson profile build barrel, while the other two are standard profiles.
Mid length gas, pinned gas blocks and carbine buffer setups, same bolt carriers.
Pulled pin and screws from gas block (non-adjustable) and checked barrel gas port which is free and clear, (gauging pin drops right through into bore) measuring a little over .070, which is spec for that barrel. Gas block lines up perfectly with gas port in barrel. Forced air through gas tube, it exited from around loose gas block. I didn't unpin the gas block from the tube and didn't pull the brake to completely remove block from barrel. Reassembled and forced air through gas tube, and it was exiting barrel.
Gas key tight and staked, no interference with gas tube when installed.
Checked carbine buffer weights, all 3oz. All springs are 11".
Range Testing
Put problem upper on known good lower from other rifle, still failure to hold open. (Problem lower worked fine with known upper.)
Put bolt carrier and charging handle from known upper into problem upper, still failure to hold open. (Problem rifle bolt carrier and handle worked fine in known rifle.)
Put spring and buffer from known good lower into problem rifle, still failure to hold open. (Problem spring and buffer worked fine in known rifle.)
Shooting M855 green tip. (Also tried a couple of different Federal SP loadings.)
Ejection pattern in 3 to 4 o'clock, about 8-10' away.
At this point it is obviously the gas system. I am wondering if I have an internal defect in either the block or the tube causing a slight obstruction. Am considering just ordering new ones.
Can't think of anything I am missing.