The 12.5 where a nice gun, the 8.5, work fine, but I think too short, your hand is out the end of the barrel, and have to watch your fingers, but as a pack gun of just bad ass ,O.K.
Neat as hell at night.
Only thing I did not like with the mag models was they are harder to carry as the balance point is right at the mag housing.
One of my guys made a 10 round mag for one, just because.