Depends on the hunting conditions. If I'm getting mostly longer shots, 40 yards or more, I'll use 7 1/2's. If I'm in a spot where the birds are coming in close, say, inside30 yards, I'll use 8's.
same as hunter said, i use remington 2 and 3/4 low brass,1 and 1/8 oz shot,7 and 1/2 on size,velocity is 1255,drams are 3 and 1/4..the code for this load is r12hd75,SHURSHOT HEAVY DOVE..