Defense Review points out another option for those looking to replace the 5.56x45mm NATO round with something a bit beefier: SSK 6.5 MPC: Best Assault Rifle Cartridge for 21st Century Warfare?.
The 6.5 MPC (Multi-Purpose Cartridge), based on a standard 5.56 NATO case wit a modified neck and shoulder, has a number of benefits over the 6.8 SPC and the 6.5 Grendel:
Ease and cost of conversion (weapons conversion), ammo capacity, and ammo weight (ammo carry capacity at a given load weight). The 6.5 MPC utilizes standard AR-15/M16/M4/M4A1 magazines and bolts, and will function in both the SOPMOD M4/M4A1 Carbine and belt-fed FN M249 SAW/LMG, provided you switch out the barrel(s). No further modification is reportedly necessary. Mag capacity for the 6.5mm MPC is 30 rounds (although you might still want to down-load it to 28, as many do with 5.56mm ammo for reliability purposes). The 6.8mm SPC doesn’t stack properly in standard 5.56mm M4/M4A1 mags, and the magazines that have been developed for it limit ammo capacity to 25 rounds, as opposed to 30 rounds, so the 6.8 SPC mags will fit inside current military mag carry pouches. You can also use 5.56 NATO stripper clips to load 6.5 MPC rounds into the mag. At present, there are no 6.8 SPC stripper clips.
6.5 MPC ammo will reportedly feed as reliably as 5.56x45mm NATO ball ammo can utilize standard M27 links (belt links) with no modification, so it will feed reportedly feed reliably through the M249 SAW. You only have to switch the barrel to 6.5mm caliber. Not so with the 6.8 SPC, which would require modification to the M27 link.
While there’s apparently a lot of resistance to switching calibers at this point in time, at least the 6.5 MPC addresses a number of the points brought up by critics of the 6.8 SPC and 6.5 Grendel. Murdoc must admit, though, that he doesn’t see any hope for any real change coming any time soon.
Major hat tip to ACE.