Whew! I didn't realize that this thread was still going on! The small Martini is a strong action and many have been converted to high intensity cartridges, up to and beyond the hot centerfires. That's too far in my opinion. I know of a Cadet, different but about the same size as the 12/15, that was barreled to a 5.6X50R Magnum. The chamber bulged but the action held up to stiff handloads. I don't know the charges. It was rebarreled to a more sane caliber and is still in use. My earlier point about rechambering the 22LR to 22 Magnum is about extracting the long straight case. I have no doubt that the .22 Hornet would extract perfectly.