I cannot find anybody locally that has one of these for my son to try out. Can someone give a comparison of the recoil of a 7mm-08 to a 20 gauge deer slug?

I'm want to get him a a 7mm-08, but don't know if I need to spend the extra $100 for the adjustable muzzle break that they claim reduces recoil by 30%. Any imput would be appreciated.

Thanks!