Help with 20 ga for 3 gun

[BrianJ]

I will be using a semi-auto 20 ga in a steel match and likely another 3 gun match.
I know, get a 12 ga and be done with it. Bought a pistol this year so there will be no more shotguns for a while.
The 20 ga seemed to work very well in a 3 gun match a few weeks ago. It is an SA-20 with a 20" cylinder bore barrel that I added an extended IM choke to.
Most targets are steel knockdowns < 20-25 yards. I used 1 oz #6 shot high brass 1220 fps. #6 is the biggest you can use. Anyone know if I can use 7.5 target shot like Winchester AA? The #6 high brass is very expensive but I'm worried about the power. Is there a better choke to use with the lighter shot?

Is there some place that has a comparison of the foot pounds of energy or muzzle energy between shells.

Any help appreciated.

 

[zagmp03]

Brian, with that load, I'd try a Mod choke. As for power, load weight and FPS should give you a pretty good idea. Depends on what the targets are too...lot harder to knock them off a Texas Star than just break a clay or some standing steel plates.

 

[BrianJ]

There was a Texas star at about 10 - 12 yds. The #6 high brass had no problem. I have no ranges around here where I can experiment. Just the first stage of the matches to test.
Kind of like closing the barn door after the horse got out. I can get both types in #6 and both in 1 oz, the difference seems to be 1165 FPS for the target loads and 1220 fps for the high brass. I do not know if the relationship is linear or if other factors affect the power more. I may just try a mix and see which works. I do not know if I can get a modified choke in time but the improved modified worked OK.

 

[mingaa]

I have no experience with 20g but in 3-gun matches that require 7.5 shot I shoot 12g with full choke or X-full with universal Williams Fire sights on a 24" rail with very good results. It's a tight group with a bit of aiming for long shots.

If there are flying clays I open up a bit to IM or mod.