First off the 7mm Rem Mag will most likely hit harder at 800 than the 300 WSM. Why? the 300 is bigger? yeah. but the 7mm has a way better BC. It retains energy and hits harder at longer ranges. If you reload your 7mm with a 180 VLD it will leave a 300 WSM in its tracks. Especially since they both start off at a similar velocity. That load is more than capable of killing anything in North America a lot farther than almost anybody has business shooting. If your 7mm is a shooter I say go for it. Being comfortable with your rifle and knowing you can make the shot is the most important aspect.
if it is a factory rifle, then loading a 180 vld will most definitely not work. The twist rate will not even be in the same ball park and the bullet will never stabilize.