Shockproof? There are many guide guns with banner scopes that work flawlessly. One fellow has in the neighborhood of 15 scoped bigbores with the same banner scope on each.
I've got one on my 444 that I'm pleased with, although admittedly I've put less than 200 rounds through it since mounting the scope. I've also used a banner on a M305, which has a rep as being tough on scopes, without any problems.
Banner would be the way to go for sure, I don't consider the sportsman as being equal to it at all.