Re: 7mm vs. 300 Win Mag
If it is a 7 rem mag, it will work. If it is a bigger 7mm all the better (7 STW, 7 RUM).
For Elk I would go with a 338 because of bullet weight, but the big 7s are more than enough to down a Elk with good shot placement and premium bullets 160 grains or larger.
Just my opinion
J E CUSTOM