6mm Grendel Group Design Project

[stanc]

I consider the lack of 30 degrees to be simply hidebound, in-the-box thinking.

That could perhaps be true of some of the world's armies. Or perhaps military cartridge designers generally chose to err on the side of cautious conservatism in order to ensure reliable feeding.

In the case of 7.62 NATO developers, the evidence shows they were not hidebound in their thinking on this matter. When development started in 1945, instead of rigidly copying the 17-degree shoulder of the venerable .30-06 case, they elected to use a 30-degree shoulder. It was only after a few years of test and evaluation that shoulder angle was changed to 20 degrees, a fact which says to me that the 30-degree shoulder likely caused feeding or chambering issues.