gwp4ever the case is the 222 Rem mag necked down to 20 cal bullet,It's a reall world 4000FPS with32 gr harnadys and with 40 gr bullets it's a barn burner at 3800FPS.One berger bullet was crnografed at 3350 FPS.In an article in the american rifleman they stooked the 32 gr to 4250 FPS and 40 gr at 4000 FPS.Thats up loading a bit but the ruger and the cases showed no over pressure problems.The55 gr bullet has a catalog velocity of3900FPS but all feel that could be stooked up to 4000 FPS.We see,the pressure is supposed to be under the 220 swift which shoots out barrels kinda fast.They don't expect the same kind of barrell problems the 220 swift has,but we will see.Drop-Shot