I have shot a 30-378 Weatherby w/a Magna Port brake, even with a round that big, you can still see your target through the scope after you pull the trigger. I was amazed at how much it reduced the recoil, but man, that @#$ was loud! When watching my brother shoot it, the muzzle blast blew my hat off from over 10 ft. Don't throw it across a truck hood to shoot unless you want to mess up the paint job.(yes, that's from experience, dad's truck, not mine).
I know a guy who threw a ported rifle (not Magna Port) across the top of his buddy's hood and when he pulled the trigger it cracked the windshield.
Jpt