There is also the matter of the .300 Whisper designed to have cases formed from .221 fireball, with the original .22 cal neck opened up to .30, whereas the Blackout was designed so cases could be formed from .223 Rem, by cutting them off at the shoulder and necking the result down to .30. Forming .300 Whisper from .223 usually requires turning the necks, the Blackout was designed to avoid this additional step. This has the effect of the Blackout potentially having thicker case necks (.334 maximum diameter per SAAMI) and some Whisper chambers may have neck dimensions too small for the thicker Blackout necks to release a bullet without excess pressures.