A friend gave me a bunch of .223 brass for my AR. I full length sized them and only checked a few for length as they seemed to be once fired. I commenced to load them. While seating the bullet , my press encountered a blockage. I immediately stopped pulling the handle and inspected the round which almost had the bullet seated. The case was a 204 Ruger. What! never heard of it. It is almost identical to the .223 Remington, but in this case the brass was about 1/10" longer in the neck department. Somehow this one odd brass got mixed in with the .223's. Had I attempted to trim or check all for length I would have discovered the problem. What would have happened if I had trimmed the case to the same 1.750 as my 223's and fired it??? After FL sizing the case looks almost the same. The long one is the 204 Ruger after FL sizing in the 223 die.