Range safety is always our main concern as a company for our employees as well as for our customers. Additional safety concerns can arise on the range when AR type weapons of different calibers are being fired at the same time at the same location by multiple shooters. Extra care must be taken when this situation occurs as chambering and firing a cartridge the weapon was not designed for can have catastrophic results, which can easily result with the many different calibers now available for the AR15 weapon system. If you are only shooting .223 Remington / 5.56-mm NATO and the 6.8 x 45-mm UCC cartridges at the same time on the range and happen to load the weapon with the wrong cartridge the results may be as follows:
Chambering a 223 Remington / 5.56-mm NATO into a 6.8 x 45-mm UCC chamber; a 223 Remington / 5.56-mm cartridge will chamber normally into a 6.8 x 45-mm UCC chamber and the bolt will close and the weapon will fire. The sound / report from the weapon will be much quieter than normal, almost no recoil and the bolt carrier will not cycle. You have just fire formed a 223 / 5.56 case into a 6.8 x 45 case, which means the case neck was expanded from a .224 diameter neck into a .277 / 6.8 diameter neck, It can be easily extracted manually. Be sure to check the bore and chamber after firing if this happens to make sure the bore and chamber are clear.
Chambering a 6.8 x 45-mm cartridge into a 223 / 5.56 chamber; the bolt carrier group will stop short of chambering the cartridge by approximately one half inch as the larger 6.8 diameter projectile will not fit into the smaller .224” diameter neck of the 223 / 5.56 chamber.