I shot many heavy kicking rifles in my home made "sled". It weighed 18 pounds and I let it recoil... it had feet made for sliding on a bench.
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Never damaged any stocks nor any scopes.
Can anyone put forth a theory on how a sled could damage a scope? There would be less recoil on the scope. Shooting standing where the rifle has freedom to recoil the most, is the hardest force a scope is subject to. Adding 18 pounds to the stock with a sled reduces the forces on the scope, not increases it.
As far as damaging a stock the sled would have to be extremely heavy. A friend of mine used to crack stocks as he weighed 375 pounds and didn't move much on recoil, stressed the bedding to the max... almost like placing the butt against a tree.