Pinning a barrel to a receiver is done for the sole purpose of keeping the barrel and receiver from moving independently of one another. If you have a receiver mounted scope, pinning the barrel to the receiver keeps it from moving and screwing up the zero of your scope. Barrel moves, scope doesn't = no more zero. If you have a scope mounted to a cantilever mount, it moves with the barrel even if the barrel moves inside the receiver. There is absolutely NO need to pin a barrel if a scope is mounted to a cantilever rail. This exact problem is why cantilever barrels were designed in the first place. Pinning the barrel was the first solution to accuracy problems with receiver mounted scopes, cantilever mount barrels were the upgrade to pinning. Instead of pinning the barrel to the receiver and making it a dedicated gun, you could buy a slug barrel with a cantilever mount and still use interchangeable barrels.
I shoot a Mossberg 935 with a cantilever slug barrel for deer hunting, as my home area is shotgun only. Every spring, I take the slug barrel off and replace it with a turkey barrel. The slug barrel goes back on before deer season. I have not had to adjust the zero once in the 4 years I've used it this way. As long as the scope stays on the barrel, your zero/accuracy will not suffer.
