Short fat seems to be the way to go to cheat more power out of the standard pattern. Those are pretty impressive results Greg. I've often wondered how much merit there would be in designing and "intermediate" AR pattern. One that didn't have the size and weight of a large frame, but gave a longer magazine to develop nice effecient intermediate rifle cartridges that would give rounds like the 6.5 Grendel a bit more clout. I reckon if done right with smart cartridge design it could make both patterns obsolete.
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