can i shoot just about any factory ammo i wish? i went to wally world and bought up 500 rounds of pmc 115gr but didnt think about if it might have some recoil issues (lack of). also, how is the pmc ammo? got 250 rounds so far in my new xd9 and loving it. one more question, besides for the obvious barrel and slide lenght what is different on the inside of the 5 inch tac and 4 in service? thanks.