Page ".300 Whisper" Paragraph 6

# Cases for the. 300 Whisper can be formed from common and plentiful. 223 Remington brass by sizing and trimming to length.

However, J. D.

Jones has recommended against this, citing the difference in case thickness at the neck ( compared to the. 221 Fireball ) as a potential issue.

This problem can be exacerbated when military 5. 56x45mm cases are used.

( The Whisper name is trademarked thus: the only firearms with a. 300 Whisper chamber are those from J. D.

Jones and Thompson Center, which licensed the name.

All other guns are cut to. 300 / 221 which has different chamber specifications than the Whisper, particularly in neck wall thickness.

Because the. 300 Whisper is a wildcat cartridge there were no established Sporting Arms and Ammunition Manufacturers ' Institute ( SAAMI ) specifications for the chamber reamers, and the necks were cut to allow for standard. 308 neck thickness, which is approximately the same thickness as produced from forming. 223 brass.

Typically only guns with Whisper chambers will have problems with. 223 brass —. 300 / 221 chambers work very well with. 223 brass, and the. 223 brass is considerably stronger than. 221 brass.