There is an option to bushing firing pins and offsetting liners. I chose to sleeve a pair of .22 barrels into the monoblock that I created from the .410 barrels, chamber for .22 Hornet, and load 50 grain cast bullets, driven at 1500 fps. The result is rimfire pressures, no need to offset the bore or the pins, etc. Also, a flat-nose cast bullet hits MUCH harder than a regular .22 rimfire.