I ordered my 300 whisper bbl form Shilen directly spec-ed out with 1:8 twist, however there is quite a bit of buzz lately regarding the 300 AAC blackout, or 30blk which is a standardized 300/221 that Remington is making loaded ammo for. Anyway.... there is some questions as to what minute differences there may be between the 2 rounds, other than .0004 (that's 4 ten-thousandths) difference in shoulder length& a slightly longer throat.
http://www.quarterbore.net/forums/index.php is a really good place for 300w info.
Bookmarks