I had one cut to 20" and it would not reliably cycle anything other than high velocity magnum rounds. And it did NOT kick any more than it did with the 26" original length barrel so I would not worry about that at all. You will probably find he is selling it because it will not function properly and if you are set on buying it you need to run a few rounds of the ammo you plan to use thru it. I personally would stay away from it or you might be able to pick up the target gas piston designed for the light target loads and that might be just enough to make it run.
CPL holder since 1991, NRA Lifetime Member, DU Member, NICET certified
"For those who would give up essential liberty to purchase a little temporary safety, deserve neither Liberty nor safety.—Ben Franklin.”