say you don't want to go to all the trouble of fabricating cases just so you can make the "jj's brit?" ™ you have no wish to have such a trick little cartridge in an ar-15 sized package.
well, then, were i you and still interested in a nice little cabin gun, i would simply buy a little lever gun in the 7-30 waters cartridge. a marlin 336 would work quite nicely, especially with hornady's "leverevolution" ammo. (that may not be spelled correctly, who cares? it is a contrived word in the first place. the thing is, the ammo has a soft plastic tip that protects primers in live ammo. that's good. trust me.)
my little brit and the 7-30 cartridge have very similar case capacities, when "chopped" off at the case shoulder. that means they can achieve relatively similar levels of performance, w/ similar powders and bullets. the edge goes to my little brit because of its far more robust case construction, and resultant ability to handle higher pressures.
a 150 to 200 lb mammalian simply won't notice the difference.
john jay @ 11.20.2012
p.s. i'd outfit the rifle with a nice little weaver scope, 1.5 to 2 power would be just about right. such a combination would be very serviceable to about 150, to 200 yards, or so. and, yes, it will go farther, if you figure out how to direct the rifle's fire.