Not so much scare as respect, Maybe the 20mm boys rifles from ww2, single shot anti aircraft rifle.
I would try the .577 but only standing up first, not off the bench.
Great guns I have sighted in for other people for pay.
1) .460 Weatherby Mag, ouch!!
2) 450-500 nitro express double rifle, not too bad, but not for very long.
3) My 6.5lb Rem 788 scout rifle in .308 with plastic butt plate. Ouch!! Don't notice it hunting though. Until you take your shirt off and see the pretty purple spot.
Did not bug me, but I had a contender in .444 marlin, that was a hoot, yes the pistol not the carbine.