Well, here's the thing. I am not quite sure about the hold over for the 7mm mag vs 300 win mag, although I would assume the hold over is less since the bullet is already lighter due to size. I am very new to long range marksmanship too, this is my first long range toy. 308 and 300 WinMag are both very popular cartridges for different reasons. The 308 is a great cartridge for long-range and it is also very cheap to shoot, that is one of its biggest attractions. The 300 WinMag is commonly used in military for long-range sniper's and is a beast of a cartridge. The 7 mm magnum and the 300 WinMag are both very, and I mean VERY, similar ballistically. I am giving a slight edge to the 7 mm magnum because the foot-pounds of energy, although possibly less by maybe 100 or 200 max compared to the 300 WinMag, is still very high but the bullets fly so flat in there trajectory that with the right round, it can't potentially be a 1,500 yard gun. Also, since this is going to be both a long-range tactical and hunting rifle, I don't need my mullet to just destroy the target in the end, and believe me, a 7mm mag definitely has the ability to destroy, just not to the extent of a 300 WinMag. Lastly, at some point in time if I ever get my press set up, I am going to be reloading for all of my firearms. Reloading for the 7 mm magnum is a little cheaper compared to the 300 WinMag and I can achieve almost identical ballistics with higher ballistic coefficient bullets in the 7mm mag. It's all about just figuring out the pros and cons in relation to what your needs and desires are.