Grendel as a Universal Infantry Cartridge

[Trooper]

Why?

The 6.5 x 55 with a modern 140 grain bullet would greatly outperform 7.62mm at long range, but there would be no saving in size or weight and not a lot in recoil. The Army would never go for that - not enough advantages. A c.6.5mm round which matches the 7.62 x 51 M80's long-range performance while achieving significant savings in weight and recoil would be a lot more attractive (and even that won't be an easy sell).

I am going by Arthur Browns comments as he is one of the big proponents of the 6.5mm in the US. http://www.eabco.com/6.5_mm_cartridges.html
In their opinion, the 6.5mm is the perfect round. But it does not gain in advantage if pushed more than 2700 fps. In their comparison, using the 6.5x55 Swede as the standard to measure against, it goal was to match a bullet weighting 140 gn going 2500 to 2700 fps out of the barrel. With those features, the 6.5mm easily matches the .308 with a 192 gn bullet out to at least 700 meters. Rounds that meet that standard are the .260 Rem, the 6.5mm BRM (based on the .30-30 cartridge), the 6.5mm Creedmoor, and maybe the 6.5x47 Laupa. With a 140 gn bullet the Grendel comes out of the barrel at 2000 fps, giving about 80% of the .308 energy at 700 meters.

The point is that if we would want to match the .308 then it is going to take a much larger casing. But if we are willing to do most, but not all, of what the .308 (7.62x51) does then the 6.5 Grendel is a good candidate for the GPC.

For long range shooting at magnum velocities, the .338 family of rounds (8.6x63NM, 8.6x70LM) give similar BC of .600 (like the 6.5mm) with less barrel wear.

Maybe it is time to move to the 6.5mm for GPC for the common infantry rifle and designated marksman with one lite MG (SAW). But move to the 8.6mm (NM?) for long range sniping and the medium MG (M240).