The DSA unit does not FF the barrel. It also requires the removal of the handguard cap. Most just cut them off, and if you change your mind DSA makes a two piece cap to replace it.
Grenadier Precision was/is going to produce a FAL version of their ARM-R railed handguard, which would FF the barrel, but so far thats only vaperware. I don't know if theirs use's the handguard cap or not.