Ok. A .575 constriction, 20 gauge, would it be better with a #6 shot or a #4 shot? Thanks.

A number 6. No question. Take those extra pellets cause with a 20 you will need them. Spring the coin for hevi 13 #7s if you can. thats what I shoot out of my Beretta 391 20 ga.

Definitely go with the 6's. Personally I would go with Nitro #7's, Hevi-13 #7's, or even Federal Heavyweight #7's depending on what type of choke you have.