I thought of that myself as well, unfortunately this would add unnecessary complexity (added parts and close tolerances) as well as added manufacturing costs which would have to translate to the product price or face low margins or lower mass interest if price were to be 'too high'. Plus, I don't think it would be too fun having to spend 30 seconds loading/unloading each cartrige/casing from a closed adapter.The adaptor could be two part. Unscrew the base, insert cartridge and screw it back on. That provides the support. The base contains spring loaded firing pin.