Why Oh WHy

[LRRPF52]

Because the military procurement procedure has more to do with the correct application of hookers/blow + nepotism than with the actual need or merit of a given product.

The Pentagon has "lost" how many trillions of dollars lately - plus the disaster that is the VA - should show you how little they think of the actual soldier and his/her needs.

From all of what I've been able to study over the past 4 decades, it's a little simpler than that when it comes to small arms, especially LMGs, and the OP's premise is a false one.

There have been several clean slate approaches to cartridge design based specifically on stated performance requirements, with a lot of engineer and ODT&E involvement, to include man-firing and testing in the hands of both new and salty soldiers alike.

The SCHV Rifle concept is one that actually gained traction and became the standard service rifle cartridge, despite all the odds stacked against it within Army Ordnance.

Institutional resistance based on logistics is a very real concern with many valid points, especially considering that our allies will be pulled into the selection of a new service rifle or machine-gun cartridge.

The .276 Pedersen, .224 SCHV, and 6mm SAW were about as clean slate as you'll ever see. Only the .224 SCHV rifle cartridge, the .222 Remington Special/AKA 5.56x45mm, was adopted en masse.