I have small Martinis in 219 Zipper and 219 Improved Zipper, my friend George the Knifemaker has them in 5-6 different 30-30-based wildcats from 22 to 35 caliber and 44 Magnum. Neither George nor I load these cartridges past about 45Kpsi or slightly above the leverguns' original pressure specs. We both, and also several professional Martini-builders, agree that the 225 Winchester as factory-loaded past 50K is slightly too much for the little Cadet's small-shank barrel. The 7-30 Waters, OTOH, is ideal (~45K) except the rifles usually end up being so light that the recoil is fairly stout (G). An inexpensive way out would be to chamber short with a 225 reamer, cut the rim recess with the lathe tool and then grind off the bottom of the resizer and set the cartridge case shoulders & OAL back a like dimension. This approach would allow use of the relatively common and inexpensive 225 Winchester reamer, dies and brass while at the same time ensuring that high-pressure factory ammo won't fit. The 225 rim is unique, you may want to cut the rim recess for the 30-30 rim and use that brass as a basis although it's somewhat of a hassle. The Donaldson Wasp is anotheer splendid choice except for the greater expense and case-forming hassle. Been there & done that on several of these & similar and can give more details if wanted.
Regards, Joe
