02-14-2013, 03:17 AM
I started out wanting to slightly improve the cartridge, thinking about expanding case capacity, increase COL, ramp up pressure, etc., but I've come to realize that it is quite awesome the way it is, and it doesn't need a lot of tinkering really.
We tend to look at the requirements of fitting in the AR15 receiver set as a constraint, but it really is a blessing in disguise: For the dismounted infantry soldier, smaller, lighter, compact ammunition configurations go a long way, as you already know. One of the biggest suck factors of the 7.62 is that the projectiles are far away from the cartridge base, so they displace weight in pouches further away from the soldier, creating an offset weight distribution scheme in length and width.
As we keep the COL low, within the length of the 5.56mm, carrying capability becomes more user-friendly for the dismounts. If you narrowed it down to a certain projectile length/weight, you can play with the gas system length and optimize it for the bullet and load you're shooting to get the most velocity. For example, you will get more velocity with a 123gr from an 18" barrel with a rifle-length gas system, with the gas port cut for running that load well, but most of the production 18" barrels have mid-length gas systems so they will run the full gamut of projectile weights reliably, from 85gr-130gr. The lighter weight bullets need more dwell time to cycle the action fully.
The biggest challenge is in making links for the Grendel case, but I think an enlarged M27 link would work fine, with the feed pawls arranged to pull the neck and base.
The other thing to tackle is bolt geometry and the barrel extension if you wanted to increase the pressure. Currently, the system runs fine when kept at 50,000psi or under, and barrel accuracy life is longer than a 7.62 NATO. While seeking downrange performance from 400-800yds, you lean towards a projectile that doesn't do what 5.56 NATO does well within 125yds, namely fragmenting or rapidly expanding.
From the big picture logistics perspective, you have to convince bankrupt nations that the 11 years of logistical capacity they currently have needs to be replaced, and can be replaced while currently engaged in a high OPTEMPO posture, in multiple theaters of the globe. The .338 Lapua Magnum and HK mini mouse guns are employed in very niche sectors of the small arms spectrum, so that feeding them isn't as large a logistics challenge as replacing the main service rifle and LMG cartridge/system.
We tend to look at the requirements of fitting in the AR15 receiver set as a constraint, but it really is a blessing in disguise: For the dismounted infantry soldier, smaller, lighter, compact ammunition configurations go a long way, as you already know. One of the biggest suck factors of the 7.62 is that the projectiles are far away from the cartridge base, so they displace weight in pouches further away from the soldier, creating an offset weight distribution scheme in length and width.
As we keep the COL low, within the length of the 5.56mm, carrying capability becomes more user-friendly for the dismounts. If you narrowed it down to a certain projectile length/weight, you can play with the gas system length and optimize it for the bullet and load you're shooting to get the most velocity. For example, you will get more velocity with a 123gr from an 18" barrel with a rifle-length gas system, with the gas port cut for running that load well, but most of the production 18" barrels have mid-length gas systems so they will run the full gamut of projectile weights reliably, from 85gr-130gr. The lighter weight bullets need more dwell time to cycle the action fully.
The biggest challenge is in making links for the Grendel case, but I think an enlarged M27 link would work fine, with the feed pawls arranged to pull the neck and base.
The other thing to tackle is bolt geometry and the barrel extension if you wanted to increase the pressure. Currently, the system runs fine when kept at 50,000psi or under, and barrel accuracy life is longer than a 7.62 NATO. While seeking downrange performance from 400-800yds, you lean towards a projectile that doesn't do what 5.56 NATO does well within 125yds, namely fragmenting or rapidly expanding.
From the big picture logistics perspective, you have to convince bankrupt nations that the 11 years of logistical capacity they currently have needs to be replaced, and can be replaced while currently engaged in a high OPTEMPO posture, in multiple theaters of the globe. The .338 Lapua Magnum and HK mini mouse guns are employed in very niche sectors of the small arms spectrum, so that feeding them isn't as large a logistics challenge as replacing the main service rifle and LMG cartridge/system.