Hi folks! Long time reader, first time poster here. I've been playing with smooth bores and cheap foster slugs for a few years now, with the predictable results that can be expected, and have dabbled in bpcr reloading, but due to an unexpected Christmas gift (mossberg 535 with a rifled barrel) I thought I'd start reloading slugs. I'm liking the looks of the lyman 525 in a waa12 wad and AA hulls, with any of the recommended powders, but should I be concerned about blasting that slug out of a 2 3/4 shell in a 3 1/2" chamber? The gun is used, and came to me with a goodly amount of lead fouling in the chamber throat/forcing cone area, and I'd rather not look for trouble in a shotgun barrel. My guess is that somebody shot foster slugs in this thing, and leaded it up either through powder gas blow by, or through misalignment of the slug as it travels through the extra 3/4" of chamber space.
Is there a load recipe for the lyman 525 in 3 1/2" shells that would mitigate this problem? Or perhaps it's not an issue because of the shotcup/makeshift sabot? I've always been told that too much free bore is terrible for accuracy, but maybe it just won't matter in this case. I thank you all in advance for your opinions.