How could or should the 6.5 mm Grendel be improved?

[LRRPF52]

c. If it is desired to match 7.62 performance, yes, a longer case is a must.

If you want to keep the peak pressure at 50,000psi, then maybe a slightly larger case or purpose-built industrial powder is needed to match 7.62 NATO velocity with a comparable BC projectile. The current Grendel case with a small rifle primer will exceed 7.62 performance quite easily if you want to ramp the pressure of the action up to be able to handle 58,000-60,000psi. The case itself will handle 62,000psi, but weapon longevity will suffer at the current configuration.

If I was in the UK, and had access to rapid-prototyping infrastructure, I would make several testbeds on the L85 and AR15 platforms, as well as the SCAR-16. The elongated longitudinal cam pin slot of the SCAR's bolt is central to its smooth recoil impulse, even though it has an off-bore axis reciprocating mass with the operating system. I would use an enlarged bolt head with beefed-up root area behind the lugs like on the .30 RAR, but use a standard-size AR15 carrier. It would be accompanied by an enlarged barrel extension, or one radiused like Knight's SR15E3 bolt and extension:



Do that, with a well-designed and manufactured extractor like the AA units, and you could run the pressures up with 123gr-130gr loads if you felt so inclined. A 130gr FMJ even will out-class even the Match 7.62 units in the 168-175gr class, when run at the same speeds, with much less recoil. You don't need to go crazy with the COL either. This would only be an appropriate DM Rifle and SASS (Semi-Auto Sniper System), as currently being filled with the L129A1 system, and would be much welcomed by the troops in those duty positions.

A 5.56 NATO will give you much better short-range performance, unless you had the assault rifle load in the Grendel with 85-95gr projectiles that would retain a substantial fragmentation range within close quarters, like the 85gr Sierra Hollow Point (non-land warfare compliant), or the 95gr AMAX (same). A 14.5" barrel M4 launching a 62gr NATO M855 is no freaking joke, especially at 2850-2920fps.

Here is an example of the recoil energy you will see with a highly-seasoned shooter with over 30 years behind rifles using a modern technique to mitigate the recoil and muzzle climb of a lightweight 16" Grendel with a 100gr polymer-tipped boat tail projectile on top of a stout load of Ramshot TAC powder, generating 2680-2700fps:

[video=youtube;qApXp7sH9QQ]http://www.youtube.com/watch?v=qApXp7sH9QQ[/video]
[video]http://youtu.be/qApXp7sH9QQ[/video]

That 100gr hunting load falls about halfway between 5.56 NATO and 7.62 NATO for downrange performance as to retained energy. A 108gr Lapua Scenar match-grade HPBT will very closely match 7.62 M118 trajectory and drift, but is a projectile that requires high standards of QC, and wouldn't be loaded into an assault rifle load.