cdb
It can be a little bit of a shock going from once fired to new brass. Ulvjaeger is right; check length, and size. You may also have to chamfer the case mouths. The condition of new brass is variable. I have had more work to do with the bulk pack brass; it seems as though there is a little less QC.
Be sure any used brass is clean. Often it is thrown into a box or bag, and it can get contaminated with primer residue. If the cases are not clean, you will score the brass, and possibly the sizing die.
