I use a poor man's version of this....Franchi Affinity 20ga with hand loaded #8.5 TSS.
setting up the same thing. either my franchi 12 or 20 gauge. It depends how well the 20 gauge tss loads I bought pattern
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I used a Carlson extra full, non extended. 200 pellets in a 10" circle @ 40 yards. I backed off to the factory full, which is 160 - 170 pellets to be a little more forgiving on closer shots. Hoping to get a red dot mounted before this season and may go back to the Carlson since I can zero the center of the pattern.
Don't speculate when you don't know, and don't second guess when you do.