As you are asking about "semi auto/tactical long range rifle" let's talk about what you consider "long range". There is one range in Ontario where you can shoot these calibers at 1000 yards, CFB Borden. Access to this range is available as a member of the Ontario Rifle Association but only on days the range is booked. Unless you have a large piece of private land somewhere, you are pretty limited for ranges.
Poking holes in paper targets at 1000 yards does not require a .338 or .50 cal. I have seen shooters using these calibers during practice, however I've never see these same guy shooting in competetion. During a competition you can figure on firing 50-60 rounds a day. Even if you could handload your ammo for $5 each (not likey with a .50 cal), one day of competition will cost you around $250 in ammo alone. I will let you do the math once you figure out the real price per round of ammo.