Gunsmithing FAL tearing up caseheads

[Ishallbie O'Cullkillin]

I couldn't log on at FAL Files, so I thought I'd cast my line here, until I get that sorted out. My FAL carbine is leaving a deep vertical mark on the case head. Viewed from the side, it appears that the rim is being bent back towards the bolt by the extractor. I adjusted the gas open to the point of barely cycling, but it still deforms caseheads. This rifle is a metric rifle kit built on a new Imbel receiver & 16" para barrel. The kit components were original parts, designed for a 21" barrel. This gun is accurate and fun to shoot, but is destroying my brass, and I'm just trying to get an overview of what could be the problems.
I just pulled the aftermarket gray plastic recoil buffer out. Maybe that's the problem. Also looking at different sized gas plug, or different recoil springs. Thanks for any feedback.

 

[sniper]

Re: FAL tearing up caseheads

I don't know FALs (we cant own them here) but to me it sounds like your rifle is over gassed. It is starting the extraction process before the bras has shrunk (its still clinging to the chamber). Like you said the gun was designed for a 21" barrel and you are running a 16".
That's my two cents

 

[Ishallbie O'Cullkillin]

Re: FAL tearing up caseheads

I took the recoil buffer out and shot the LC brass, 44gr Varget-168gr Smk load yesterday, with slight improvement. Some cases look good, while others get the rim bent. Gas setting is one click past minimal. Word at the Fal forums is to run Nato brass, but my 168gr Amax-43.8gr H-4895 load using Winchester brass never shows bent rims. Faster powder, roomier brass, or stronger brass composition? I want to use the L.C. brass and the 168smk combo for the Fal, because I'm sitting sitting on a modest stash of this stuff. I'm going to try H-4895, Tac, W-748, & may even try a light load of X-terminator.