Buckshot at 50 yards that is not flight control, buffered, etc is not going to have tight patterns. Brand matters, but you will just have to experiment. Usually, one can find something in IC to IM that will work decently enough.
Realize that the buffered and FC buck is intended to be shot through Cylinder bores for the tightest groups.
I shoot an M2, and some of the cheap buck, like Estate, will do okay with LM where the Fiocchi tends to prefer M.