I had to clamp my upper in my vise blocks to get the flash hider off. Mine was on tight I could not hold on to it with one hand and turn the wrench with the outer.
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...