There was a guy that did some testing on .209 primers to see how they ranked from an explosive standpoint, using a bullet shoved against the breech plug without a load of powder. He'd drop in a primer, pull the trigger, then measure how far up the barrel the bullet went to determine how hot the different primers were. While the test isn't super scientific, it was interesting...

I can't find the darn link to that test now after much looking. Anybody?