I tried boiling one- it would not get any softer.
Other than black powder, or shooting milsurp commie ammo, hot water really does not do anything better. The crud you are trying to get out is not really water soluble.
Back in the day of the 03 Springfield and Garand, when you were going to have a "white glove" inspection, it DID remove every trace of oil or grease. The military finally realized this was a bad idea, and dropped the white glove insanity.