That at least has been addressed since the dlask came out. Some members have chronied their 8.5's against longer barrels.
There is a loss of speed - as you'd expect. It takes about 12 - 14 inches of barrel to reach max velocity (depending on the load.)
However - it is VERY minor, and is not of any significant concern when looking at the gun's intended purpose. You can't legally hunt with it here in bc (there's a 12 inch barrel restriction for all hunting arms) but as a holsered bear defense tool while you're hunting it's awesome. Lots of people put down their rifles to clean game etc, and bow hunters might well appreciate it too. Hikers who don't want to shoulder a gun could find it the perfect answer - especially as the gun can fire flares and bangers as well, and could fetch a grouse or squirrel in a survival situation.