bad advice, if you try and shove .020" of brass into the case you will crumple it. Not only that, but you can't run a loaded round into a sizing die, it won't fit with a bullet. The die makes the neck very small, then the expander opens it back up to seat a bullet.
While this may chalk one up in the annals of lethal curiosity and bad ideas, I decided to test these assertions by running some fully loaded 223 (77 SMK over 25 grains of Varget) into a Forster sizing die, screwed down a touch more than usual (I size to SAAMI max length) with the decapping pin removed. The sizing process was uneventful and seemed no different than with an empty case. The resulting rounds were SAAMI minimum as measured in my case gauge and dropped in and out of my AR's chamber without difficulty. Pulled a round and saw no signs of over-crimping and the seating depth of the projectiles was unchanged from prior to the sizing operation.
Shot 5 of these at the range today taking some precautions in case of the big Kaboom and pulled the trigger with a heavily gloved hand and......the gun went bang in a totally uneventful manner. The same happened with all other rounds.
Now I'm not going to say sizing a fully loaded round is a good idea nor am I trying to dismiss other folks' experience but thought this was an interesting experiment. Of course, differences in equipment, components and technique might result in completely different results and the risk of igniting a round while sizing while small, would likely be catastrophic. Not planning on doing this again.


















































