you're comparing 243 ammo to 300 mag ammo? ie 300 win mag? I think those are 2 different categories, and 17-20/box doesnt sound all that cheap for .243 ammo, i know prices have been going up, oh well still is cheap compared to 50-70/box ammo. but ya if you want it/like it, get it. buying a dead or unpopularround would definitely way in on my decision making...I'd buy a 6mm rem I think before a .243 wssm, but I'm going with a .243 win over both.