06-06-2021, 06:00 AM
My understanding is that the goal was a particular amount of energy delivered at a particular long range, using EPR (Enhanced Performance Round) bullets. These bullets are made with steel and copper, similar to M855A1, but with higher BC. The lower density of the EPR design vs a lead core bullet drove the need for a diameter larger bullet to meet whatever goal they had set. I know that Textron was working on a 6.5mm cased-telescoped cartridge that utilized a lead-cored bullet prior to the NGSW project.
Of course, the actual relevance of the Army's chosen goal is up for debate.
The switch to lead-free bullets has affected other projects. I had contact with the fellow developing the .277 Sidewinder round for potential military approval a few years ago. It was actually a cartridge based on the 30 Remington that his father had started on several decades ago. He had based the round on achieving a certain amount of retained energy at something like 800 or 1000m. When the Army switched away from lead-cored bullets, the BC's on bullets that fit his cartridge dropped to where he could no longer reach his goal.
Of course, the actual relevance of the Army's chosen goal is up for debate.
The switch to lead-free bullets has affected other projects. I had contact with the fellow developing the .277 Sidewinder round for potential military approval a few years ago. It was actually a cartridge based on the 30 Remington that his father had started on several decades ago. He had based the round on achieving a certain amount of retained energy at something like 800 or 1000m. When the Army switched away from lead-cored bullets, the BC's on bullets that fit his cartridge dropped to where he could no longer reach his goal.