Hello, everyone.  I have been looking in the 2011 Huntington's RCBS catalog, and cannot find either dies or brass for the .255 Jeffery Rook ctg.
   I have read where it can be made from shortened & probably fire-formed .25-20WCF. brass?
   I know slugging is the final test..but I wonder what nominal groove dia. would be?
    Any information would be greatly appreciated!
Wishing each of you a Happy New Year!

Hello 22-5-40,

Your correct the case can be made from 25.20 Winchester cases. The nominal bullet size is 0.255". Bullets for 0.25 pistol cartridges will also work according to Colin Greenwood the author of 'The Classic British Rook and Rabbit rifle'. The Standard load was a 65 grain lead bullet in front of 9 grains of Black Powder. Smokeless powder may be used but keep the velocity of the bullet to 1200fps. These rifles do not take well to high velocity loadings. Greenwood also says that Berdan primed cases can be met with. (but they're real PITA to reload).

Rook and Rabbit rifles are a delight to shoot but their ammunition restricts them to a little over 100 yards for small game and vermin shooting.

Have fun,

Harry