any michael mann movie (heat, collateral, public enemies, miami vice) has good gun play. and by good i dont mean action heavy or tons of rounds, i mean realistic. as in the director clearly had all the actors take training prior to filming (in fact the special features of miami vice show some of the training)
way of the gun, as mentioned earlier in the thread, has some of the best gun handling i've seen in a movie. even wounded, one handed combat reloads. fantastic.
open range, if youre into western style stuff, has a real nice final shoot out (they aim!!!)
shooter, with mark whalberg, is actually pretty good gun ****, has a few room clearing scenes and AR stuff, and some nice bolt action ****.
tears of the sun, as mentioned above, is well done. starts slow but when the **** hits the fan, it really hits the fan, and the gun handling is done very well.
naturally, saving private ryan AND band of brothers are fantastic and, frankly, i think everyone should watch, if not own, band of brothers. its fantastically done miniseries.