I see your -20 and -5's and raise you a -10.
AC/10 with 10 rounds sound more like an onslaught, verse a 20 that an miss. Whoops, I missed and ruined my shot... meaning you should 'EEk! Kills it! Kills it, NOW!' vs. 'Oh look, we got a sniping AC/5 downrange, lets close in to make its life miserable.'
Say that to my annoying AC/10... and watch as I make you pay for the ground you just crossed.
TT