What brand of .580 you going to be testing? If you are not set on the .580, you might try a Carlson .575. According to others on OG, it seems to open the pattern up for perfect coverage in the 10" and 20" with TSS. Great pattern either way.
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I got the TC extra full that came with the gun. This pattern is great I just think it would help at closer yardage to be more even. This is Hal's recipe. Great guy who knows his loading and helped me out alot ( this was my first time loading).