Blowing the pattern?

[Double Lab]

Well good luck with your 28 Dylan. Unfortunately it seems your barrels are fixed choke which is not a bad thing. What is bad is them being choked as they are. Keep experimenting and you may find the right ammo for your gun. Open chokes don't belong on a 28 or .410.

[Drew Hause]

Randy: re the Super Fox loads. You are no doubt aware that the velocities listed are the "average velocity" over 40 yards, not muzzle velocity.

In a 1927 Western Cartridge Co. flyer “Super-X The Long Range Load” by Capt. Chas. Askins the 12g “Duck Load” (not specified but presumed to be 1 1/4 oz. Super-X “Field”) is described as 3 1/2 dram (38.5 gr. DuPont Oval Powder = 11 gr. / Dr. Eq.); at 1400 fps (at the muzzle rather than 3 feet) and 1000 fps average over 40 yards, with a breech pressure of 3 3/4 tons or about 8,400 psi + 10-14%
3” Super-X “Record” with 1 3/8 oz. at MV 1400 fps with 4.25 tons = 9,520 psi + 10-14%

Super-X 10g 1 5/8 oz. “about 4 1/2 Drams” No. 2 shot Full choke 32” barrel, average velocity over 40 yds. 1030 fps; “up to 13,000 psi” by crushers = about 14,500 psi by modern transducers.
In 2025 Tom Armbrust tested 3 vintage 2 7/8” Super-X 10g 1 5/8 oz. ‘Maximum Load’ at an average of 1300 fps. And 19,166 psi.