First, get the "cyl" choke measured. Often enough cyl runs .001 or .002. Believe it or not, .002 will get you to IC with some loads.

Second, most cyl barrels (even .000 true cyl) do not throw true definitional cylinder (40%) patterns with modern shotcup ammo. I get a kick out of folks decrying the poor patterns they get with spreader loads. Usually, they are really just bashing a true cylinder pattern. My .000 12 ga M21 barrel would give almost LM patterns with B&Ps. So experiment with different loads.

I'm more of an IC/M or IC/IM fan, but cyl/full can work with a bit of ammo testing.

Sam