The shorter the barrel, the better the pattern and greater the effective distance. I use mostly from J frame 2" barrels, my own load with #12 shot built on John Taffin's load, and .44 spec from a 3" Mod 24.

Within 10 ft both work well. I think the reason they caution against use on ported barrels is the danger of tearing the plastic shot capsule in the ports and/or plugging up the ports.

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H Richard
SWCA1967 SWHF244