Pete,
The 410's total energy is pretty low. While the pressures may be fairly high, the guns are typically not scaled to strength required, but rather are much stronger than necessary...most of the time. Maybe you can post what types of guns you have and a better eval of your concerns might be forthcoming from the members.
My Nitro Specials are very strong considering the size/pressures/recoil of the 410. As such, I feel no concern shooting modern factory standard and 3" mag shells in one of them. My chambers had been elongated poorly to 2 1/2 or more. The cones were a mess, so I had a friend custom grind a long forcing cone reamer that fit the original chamber cuts and reamed them to 3" to clean them up. Wall thicknesses are very generous.
