Winchester super x shotgun ammo

[jungleboy]

I have some older Super X 28ga shot shells that came in the grey box, I have been using this fall. I have never seen shot shells leave so much residue in a barrel. I have to clean it and I mean scrub it after each outing which could be anywhere from 3 to 5 shots at birds. It builds up almost like black powder in a muzzle loader. It does seem to affect the pattern it gets so bad. has anyone experienced this ? This is my first year with this little 28 it's a break action Turkish made gun with a 20" barrel.