So here is an update on my Marlin 336ER.
First of all I started over with slugs made from a mold using two blocks of wood. This gave me a better surface to measure than the egg shaped fishing weights I was using.
Turns out my barrel slugged at dead on .358 until the rear sight dovetail, which swagged the slug down to .3577. That is not a lot,…[Read more]