{TAIL ~ Each} of said walls defining a secondary receiver chamber sized to receive {HEAD ~ a magazine cartridge} of rounds a shorter length than otherwise provided for in a rifle 
{ TAIL ~ Each } of said walls defining a secondary receiver chamber sized to receive { HEAD ~ a magazine cartridge } of rounds a shorter length than otherwise provided for in a rifle
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH