devil dog

So the rest of this will make sense, the following dimensions are all based on an overall cartridge length that will have a Sierra 80-grain MatchKing bullet just touching the lands when the round is chambered. We don't all shoot Sierra 80-grain MatchKings, and we don't all set them to touch the lands, but most competitive High Power Rifle shooters do both. At the least it's a "standard" that gives us a point to work from. What I call the "Derrick Chamber" (Derrick Martin of Accuracy Speaks) needs an overall cartridge length of 2.442"; the "Wylde Chamber" (for competition-use AR-15 pioneer Bill Wylde) is 2.445"; the "AMU Chamber" (for U.S. Army competition team) is 2.500". There are others, but these are the most popular among competition rifle builders. A SAAMI chamber is normally about 2.410"; a NATO chamber is normally about 2.550". Those are huge differences, and I counted five different reamers just mentioned here.
Ridge Runner, here is just some info on some chamber sizes, I'll try to find a website I was on befor, it showed the different chamber sizes in blueprint form. As you can see, the Wylde chamber is in fact .105 shorter than the NATO chamber.