searcher
Gold $$ Contributor
If you intend to shoot brass that has been fired in other rifles (especially military brass), you will want to run it though a short-base die. While a lot of the brass you may size will not actually need the short base die, it is the few or more that do require it that will cause you chambering issues - so you size them all to be sure you are covered. Some chambers will dictate whether you will need to continue to use a short base die after the first firing, but it usually is not necessary - it depends on the chamber. I have a few chambers that require it, though most do not - especially if they are factory rifles. If you are using new brass, short base dies are rarely needed - though there are exceptions. Always best to work up several dummy rounds (no powder or primer) to allow them to be stripped off the magazine and loaded into the chamber. If you are able to get the trigger to fire and when you pull back on the charging handle, there should be no noted resistance to open the bolt and eject the cartridge. If the bolt is not closing all the way or the round does not easily eject, this points to the possible need for short base die. You do not need to crimp as long as you are getting enough tension on your bullet. Getting a sizing die that takes bushings allows you to control the level of tension on the bullet. If you load some dummy rounds off the magazine and let the bolt slam home, re-measure the OAL to ensure the bullet did not slip a bit into the case. It is a good idea to do this test at least a day after you sized your brass, as if the tension is marginally good, the necks tend to open up just a little after sizing - and that can continue for a day (sometimes a bit longer). If you anneal you anneal your cases, that "spring back" is greatly mitigated. If the bulet slips back into the case, you get erratic pressures and poor accuracy.
