Free: Contests & Raffles.
I guess I'm curious as to"Why" you don't like a modified choke? I use nothing tighter than modified in a flush mounted choke in my guns and in my O/U's, I use improved cylinder / modified. With steel, you should be getting a lead-like, full choke pattern with your modified choke.I think your problem in killing ducks maybe in the shells / shot size you are using and not the choke. I would pattern your gun on a target sheet at 40 yards.
As T-Bone said, you should get a full choke pattern with a standard modified choke. If you pattern your gun, and get 70% of your shot inside a 30 inch circle at 40 yards, that is a full choke. No matter what your choke tube says. Your problem in killing ducks could also be that you are shooting too far.
I don't hunt waterfowl much anymore so I'm not really up on the aftermarket chokes. But with my 870 I used to use the improved cylinder tube most of the time. The improved cylinder choke tube gave me an 85% pattern, which is tighter than a full choke pattern. You really should try an improved cylinder choke, especially with larger sizes of steel shot. You might be surprised at the patterns it will throw. Also, take a rangefinder with you when you're duck hunting. You might find the shots you thought were 40 yards are more like 60 yards.
also, try to stick with the same speed shells. a couple hundred FPS can really throw off your shooting.
Dont shoot BB's through a full choke