I have seen 16" bull bbl,s at the range where they were shooting 100yds to 200yds and with target scopes,making 1 hole groups even at 200yds.(under 1/2").This was slow fire. But you are talking reddot,a hunting sight system so I take it you are going to do some fast shooting.(spray&pray).A bull bbl might help on barrel flip so you might do very nicely but the cooldown would be long I would emagine.A lighter bbl might get you back to shooting faster. sam.