US Patent 11428485 Firearm with field-replaceable blank-fire chamber preventing chambering of live rounds

A firearm for firing case-telescoped (CT) rounds includes a barrel configured for transit of a bullet of a live CT cartridge in a live-fire operating mode. The live CT cartridge is chambered and fired from a live-fire chamber installed in the live-fire operating mode. The firearm further includes a blank-fire chamber configured to chamber and fire a blank CT cartridge in a blank-fire operating mode, wherein the blank-fire chamber has a second diameter less than a first diameter of the live-fire chamber, to prevent chambering of the live CT cartridge in the blank-fire operating mode. The arrangement can enhance safety by preventing accidental firing of a live round during operation when it is assumed that only blanks are being fired.