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12/21/2016 9:11:29 PM EDT
My 11.5 pistol has been short stroking recently on poly Wolf 55 FMJ.  I don't recall it having trouble before, but I've made some changes recently and I'm trying to locate the issue.
The barrel is a non-chrome lined 556 chamber Shaw from 2005 when I first built a pistol. Bolt carrier group is standard FA. I recently switched to a Sig pistol Brace kit.  Various GI mags. Standard carbine buffer. Gun will run brass ammo, including my reloads, but chokes on poly Wolf. This wolf ammo clocks at about 3000 fps out of my 20", so I don't think its underpowered.
I've tried replacing all the gas rings, checking the buffer spring length, comparing the buffer tube length between the pistol tube and a carbine tube, still short stroking.

The newest change was the Sig brace, but it looks to be no different internally to a carbine tube.
any thoughts? Thanks.
12/22/2016 1:34:24 AM EDT
[#1]
what's the ejection pattern like? when i put an adjustable gas block on my 10.5 suppressed upper, i found that as i turned down the gas my cases went consistently from 2 o'clock all the way to about 5 o'clock. might be helpful in diagnosing your issue.
12/22/2016 8:34:01 AM EDT
[#2]
Seems you already diagnosed it to the ammo. But, if it ran Wolf before without issue, why the issues now?
Assume chamber is clean? Would suspect this ammo you ate running is of a different lot number and it's a tad bit underpowered.
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