7rem mag for competition ?

Typically it's gonna be a bit overkill. Recoil will be rough, powder consumption will be rough, and barrel life isn't great for tactical matches. On faster stages a long bolt throw and heavy recoil can hinder you. With that said you could still compete quite competently with it and hit all the same targets.
 
IMO, too much gun for tactical matches where most of the steels are inside 700Y. I tried one for a few matches but it didn't work for me because of the recoil and sight picture upset. I was shooting 176's at 3045 fps. I sold it but if I were to ever try again I load down some 168's.