From Les Baer Custom... 6 X 45 Caliber
A Modification Of The 5.56 For Superior Down Range Performance

Who would have thought that simply necking up a.223/5.56 case to 6mm could have made such a huge difference in performance? Les Baer tested this dynamic new caliber until he proved to his own satisfaction that 6 X 45 is a logical (and in many cases a much better) alternative to the traditional .223. The ballistics and the performance are phenomenal!
The barrels for the Les Baer rifles chambered for this new caliber will be available in either a 1 X 8 twist for 100 grain bullets and up, or a 1 X 9.5 twist for bullets weighing less than 100 grains. All rifles will come with two magazines, but all magazines and other parts for AR .223 rifles will interchange with rifles chambered in the new 6 X 45 caliber!