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Posted: 7/13/2015 6:50:51 PM EDT
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Guys,
About a year ago I picked up one of these from PSA, a 16" model w/o a brass deflector or a dust cover. Got a really good deal on it and thought it would make a great range toy. The rifle seems well built and is very accurate. I'm getting slightly larger than silver dollar sized groups at 100 yards using a 1.5-4x20mm Leupold scope with bulk ball ammo. After a thorough cleaning I can get maybe 10-12 rounds through it before it FTLs. Once the problem starts the bolt carrier will strip a round off the top of the magazine, but won't load it. The round ends up lodged crooked in the upper behind the chamber lugs with the bolt about 3/4 of the way forward. I can pull the bolt back and lock it open, drop the mag, remove the stuck round, replace the mag, press the bolt release, and another round chambers. I fire it, the bolt cycles and I end up with another FTL. I've tried different mags (factory DPMS and Pmags) with no noticeable difference. Ammo is Federal Lake City XM80 150gr ball. Does it sound like the rifle it short stroking? Anyone with a .308 AR try this ammo and have a similar result? My next time out I'm going to try PPU 145gr and see if there is any difference. My next change will be to a heavier buffer spring. Does it sound like I'm on the right track? Thanks for any thoughts! ETA: The rifle has about 60 rounds through it. |
| It does sound like its short stroking. Check your gas rings and gas key first, make sure the key is not leaking. Then check your gas block to see if it has moved and while there, check to make sure no hole or crack has developed in the gas block and that the tube is still sound. |
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Does it have an aluminum gas block by any chance?
They are notorious for the CLGS aluminum gas blocks burning out and leaking gas. Look around your gas block and see if there is a lot of carbon leaking out. The first thing that needs to be done to any of the guns with a CLGS or MLGS and a cheap aluminum gas block is to remove that gas block, and replace with with a steel one that is well fitted, and correctly aligned to the gas port. |
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I checked and the gas block is aluminum. I didn't see any carbon around it, but the rifle has a low round count. I also wiped it down pretty good after I shot it, possibly removing any evidence, and
I haven't had it apart yet. So (assuming the gas block is the problem), when cold, the possible leak is less noticeable, but as the rifle heats up the tolerances increase, more gas leaks, and thus the short stroke? |
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Quoted:
It does sound like its short stroking. Check your gas rings and gas key first, make sure the key is not leaking. Then check your gas block to see if it has moved and while there, check to make sure no hole or crack has developed in the gas block and that the tube is still sound. Thanks for the tips. I'll check these things when I disassemble it for cleaning. |
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Those rifles like to run wet. Including the buffer tube! Yes! The buffer tube! If you look at the inside of the buffer tube, there are little ridges - it's not completely smooth. If it's dry, the spring will catch on the ribs, and it short cycles the buffer. Lube the hell out of the buffer tube, and the spring. Lube the hell out of the bolt carrier assembly. These are especially important when the gun is new. I'll bet this will take care of it. |
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