The choke I use to get 55% patterns at 30 yds depends on the shell that I am shooting. Which means that I match the choke to the shell, after pattern testing. No single choke will shoot all shells to the same pattern density. I have proven this many times. One of my favorite recipes to get a 55% patt. at 30 yds is...Rio Star Team shell, 1.125 oz. No. 7.5 shot. in a 26" barrel, with a SKB modified choke in my SKB XL1900, 12 ga. shotgun. The Rio Game Load shell shoots the same pattern, with 7.5 shot. Another good combination in my gun is the Federal Field-Target shell, 1.125 oz. No. 8 shot, 1200 fps. with a Carlson .690" dia. choke. This combo gives exactly 55% at 30 yds. even though I'm using a full choke.
Its productive to remember that shotguns do not shoot the same pattern density, even when using the same barrel, same choke, and same shell, at different yardage. If a certain combination shoots 60% at 30 yds. it is almost for certain that the same combination will not shoot 60% at 40 yds. More like 45%-55%. This is known as excessive linear dilation.
It takes a lot of time and patience to do shotgun pattern testing. But I feel the benefits are worth while. Even if I never use the knowledge gained, I will know that some Joe-Blow at the local gun store is blowing smoke when he says that his Benelli shoots all shells the same. B. S. on that!
Proof enough that a guy can't predict how a gun/choke/shell combination will pattern is in your following statement:
"Another good combination in my gun is the Federal Field-Target shell, 1.125 oz. No. 8 shot, 1200 fps. with a Carlson .690" dia. choke. This combo gives exactly 55% at 30 yds. even though I'm using a full choke."
If I got those results the first thing I'd do is pattern about four more rounds. Measure the choke, pattern four more. Then call Carlson's.
