I don' t know how well some autos would feed with the shorter rounds? I don' t shoot autos myself, probably never will again and never did a 20ga, always 12ga 3" er' s, but a buddy of mine shoots a winney if I recall correctly, and it doesn' t feed 2.75" rounds at all basically. I' ve heard of similar problems with .410 autos, trying to feed 2.5" er' s in 2.75" chambered arms. Something to consider?