The .260 Remington is a niche long-range rifle cartridge, that lacks something the .308 has in strides: barrel life. While the .260 Rem has great barrel life compared to 6.5x284, .300 WM, and .338 LM, it is still too short for a military general issue weapon, and is still in the battle rifle size class, since it is a necked-down .308 Win.
The performance of the .260 Rem is definitely advantageous for a sniper or DM, but way more than a rifleman needs. It is possible to get .260 Rem performance from an AR15 action, but you need a fat case in excess of the diameter of the .308 Win., which is a non-starter for military use. I also don't want a 140gr high sectional density projectile exiting a rifleman's muzzle at 2700fps within close quarters from a high pressure chamber. That is a bad thing from a practical perspective in my opinion, for a number of reasons:
* disorienting effects of muzzle blast and overpressure
* muzzle climb and recoil on a lightweight weapon
* effects of high pressure on barrel, bolt, receiver, and reciprocating parts life
For COAL, once you start getting to 2.500", you're pushing the limits of the intermediate cartridge concept towards something that is significantly heavier, and will occupy more space on the soldier's load.
With what I've observed of the existing 6.5 Grendel's performance with 123gr OTM, I see no need for more velocity. The question then becomes how to mass-produce a military projectile with a BC of .510, while still being able to achieve 2350fps from carbines, and 2500fps from a Light Machine Gun.
Even a 12.5" Grendel carbine can push a 123gr to 2300fps, if not 2350fps with canister powder and the right components. I think Variable is able to get 2179fps with the 123gr A-MAX from his 10.5" Grendel.
The real area that needs improvement is the current status of our belt-fed, Squad Support weapons, and the decision has to be made whether or not a new caliber should be exclusive to it, or should it share a chambering with carbines/rifles. I personally think the performance requirements of the LMG are different enough to warrant a separate chambering, but one that could be common with Semi-Auto Sniper Systems (SASS), as well as DM carbines, but that goes against the General-Purpose Cartridge concept, which prioritizes logistics over performance.
The performance of the .260 Rem is definitely advantageous for a sniper or DM, but way more than a rifleman needs. It is possible to get .260 Rem performance from an AR15 action, but you need a fat case in excess of the diameter of the .308 Win., which is a non-starter for military use. I also don't want a 140gr high sectional density projectile exiting a rifleman's muzzle at 2700fps within close quarters from a high pressure chamber. That is a bad thing from a practical perspective in my opinion, for a number of reasons:
* disorienting effects of muzzle blast and overpressure
* muzzle climb and recoil on a lightweight weapon
* effects of high pressure on barrel, bolt, receiver, and reciprocating parts life
For COAL, once you start getting to 2.500", you're pushing the limits of the intermediate cartridge concept towards something that is significantly heavier, and will occupy more space on the soldier's load.
With what I've observed of the existing 6.5 Grendel's performance with 123gr OTM, I see no need for more velocity. The question then becomes how to mass-produce a military projectile with a BC of .510, while still being able to achieve 2350fps from carbines, and 2500fps from a Light Machine Gun.
Even a 12.5" Grendel carbine can push a 123gr to 2300fps, if not 2350fps with canister powder and the right components. I think Variable is able to get 2179fps with the 123gr A-MAX from his 10.5" Grendel.
The real area that needs improvement is the current status of our belt-fed, Squad Support weapons, and the decision has to be made whether or not a new caliber should be exclusive to it, or should it share a chambering with carbines/rifles. I personally think the performance requirements of the LMG are different enough to warrant a separate chambering, but one that could be common with Semi-Auto Sniper Systems (SASS), as well as DM carbines, but that goes against the General-Purpose Cartridge concept, which prioritizes logistics over performance.
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