Lyman 525 slug: Rifled vs smooth bore

[littlejack]

megasm:
I realize that by the time the wadded slug gets down to the choke, the psi has dropped considerably. So, I will continue to try different recipes.
Thank you all for all your suggestions, experimental R&D and information.

[megasupermagnum]

An I/C choke is nothing to worry about, it won't be harmed by the slug. In that HCD wad, sizing is fine, but you will want to use the unsized slug In the AA wad. The sizing down will hurt accuracy unless you have a very tight bore. The wads being pinched off are likely not in the choke. When you fire, the slug expands. This is made worse if your wad tries to force into the hollow base, but they do expand just from the inertia of being fired. The goal is to get the slug and wad through the forcing cone, and into the bore without ruining the wad. Too loose, and you get no accuracy. Too tight, the petals fail, and you get no accuracy. At 25 grains of Herco, you are likely near the top of the pressure range. It's safe, but appears to be the wrong combo for your gun. Back off to 20 grains, and work up in 1 grain increments. Stop right where the petals begin to shear off.