When you say load long 9mm, do you mean use 9x19 casing in the 9x21 chamber? If I'm not mistaken, the 9x19 and 9x21 bullets seat in the chamber on the case face. If I were to load 9x19 then the casing is only held by the extractor.... am I missing something? Is that what you do?
Right now my 9x21 rounds are loaded to 1.250", not sure if the gun will feed a shorter load.... I've never tried it before.