If the barrel bore diameter of your Parker Mountain Machine barrel is a just a little on the larger side, 0.0003\” just MAY be enough to exacerbate the fouling.

I actually prefer 0.356\” diameter 9mm bullets when shooting lead bullets, because I have a few barrels that slug a little on the large side. They shoot much better with the 0.356\” bullets, and have less fouling than 0.355\”. Copper jacketed bullets don\’t seem to be as sensitive to my slightly larger bore diameters. Perhaps it is the same with the Zinc jackets.

Also, the barrel – cylinder gap MAY escalate the fouling issue in your Ruger LCR.

I have to add: I have NOT personally tried RMR\’s Silver jacketed bullets myself – yet! I am offering this advice, coming from my experiences with lead bullets, and since the zinc jackets are known to be softer than copper jackets, well…

If you want to slug your bores, Meister Bullets sells slug kits: