Some folks ask about parts required. No parts are required to convert a 686 or a GP100 to .41spl or 10mm. All the good smiths send the barrel off to be rebored, and properly size and chamber the cylinder. Since the specs are controlled,as opposed to a long production run, they are tighter, and accuracy is more assured. EDIT I have been shooting 6grs Unique and 6.5grs Universal under a 215 commercial cast swcbb, but today I fired some with 7 grs of Power Pistol. I am pretty sure this will come close to 1,000 fps in a 4in.

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dd884
JMHO-YMMV