6.5mm MPC

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.

Read the whole thing at Defense Review, and also be sure to check out the SSK page on this offering.

Major hat tip to ACE.


  1. Infantry magazine had an article on possible alternatives to the 5.56 a few months back. Both the 6.5 MPC and it’s 6mm cousin were mentioned. Not sure if Google can find that article. The magazine’s home page isn’t accessable without a DA login.

  2. The M-16 will be replaced when: A) Colt goes out of business; B) Senator Dodd retires. C) Hell freezes over. D) We lose 50-60 men in a battle and the 60 minutes expose reveals that the troops died because of ineffective weapons being forced on the military by a corrupt politician(s).

  3. D) won’t happen, the media is too busy reporting rumors from hard-to-find Iraqi police captains to perform any real journalism. Sorry to be so cynical. P.S. Why did Murdoc bother posting about a replacement for the M-16/NATO 5.56mm? Surely he knows nobody is interested in discussing that 😉

  4. Let me slam the US Army in a constructive way. The M-16 was adopted in my humble opinion, by the Army because the Army had abandoned any hope of ever hitting a tartge with one round. I say this because of the sights on the M-16. Remember how much fun it was tryin to adjust them with a 5.56 bullet? There were also those psydo-intellectual studies on the common rifleman and how inept he was at one shot one kill. So the philosophy became … turn it on ‘sprinkle’ and let fly. More troops shot themselves defenseless with full auto fire on those poodle shooters than any rifleman ever did with a Springfield, M1, or M14. My son … who just recently was selected in the Army for Special Forces, noticed how when you turn the danged thing on ‘A’ you have in effect 10 shots with the M-16 family of weapons (10 three round bursts). Reading Col Coopers journals, it seems like it takes three rounds in the chest to effectively stop a bad guy. That means on ‘A’ the M-16 has in effect two more ‘shots’ than the M1 and a 10 less ‘shots’ than the M14. In my experience working directly with and in some cases for the US Army, I have been repeatedly disgusted with the psydo-intellectualism at such places as the Fort Leavenworth College of All Knowledge concering the nuances of effectiveness than I can mention. I would like to … once again… call ‘bullshit’ on all those who support the M-16 family of weapons. It is full of birth defects.

  5. jim b.. I think you mean ‘pseudo’, not ‘psydo’? Otherwise, you seem to be on the mark to me. The assumptions which justified the introduction of the M-16 are no longer correct. There is no more draft. Riflemen are highly trained and accurate. Either 7.62 or an intermediate calibre round seems like a far superior option at this point.

  6. m16 was kind of a kludge, being of civilian origin but it was the only game in town for an assault rifle in the early 1960’s. Springfield armory screwed the pooch and was disbanded in the late 60’s with the m14 debacle. Fine weapon but plagued with development/production issues and a 10+ pound 3 1/2 foot weapon was not what was needed for the future. Also uncontrollable on full auto by most troops. Worst of all worlds. Army adopted the m16 mid 60’s (only choice) and I think many of the 5-6 million m14’s went to the torch unissued in the 90’s. No way the Director of Civillian marksmanship was going to issue these like the Garands. (Easy to convert to full auto and congress went nuts) With loads of troops on foot and unmechanized in the jungle, you could not have fought the Vietnam war without the m16, and the loads of ammo you could carry and firepower. Precision was of less importance than firepower at night and close quarters. Were there the jamming issues ? Was it perfect ? Sure and No. But the only game in town. I know you guys in mech units and security forces loved the m14, but you may not have had to hump the ammo for it (nearby in jeeps and tracks hopefully) Interestingly enough the royal armory in Britan also screwed the pooch ‘royally’ with the Bullpup design. Almost 10lbs for a 2.23 rifle and plagued with reliability problems that make even the original m16 legendary like the ak. All to get a rifle shorter like the 6 lb m16 CAR with 10% more muzzle velocity. Looks like the m16 will be with us for awhile, although with body armor now with plates available to stop even the big 7.62 stuff becoming more commonplace, one wonders whether an intermediate round would be useful or considered for the future. Or just better training to ‘shoot around’ the thickest armor. M14 seems to have made a bit of a resurgence with the many mobile troops in the urban environment and the longer ranges in afghanistan and issued in modest #’s. (I think there are about 190000 left in stocks, more than enough for special use for many years) I think they offered them to other countries and they only managed to give about 50000 away. With a production of about 8 million (with civillian versions) the m16 ar15 has withstood the test of time. Please spare the 50 year conspiracies of the m16 being there because of profiteers etc. Even the CAR version of the m16, with its reduced power is a cannon compared to the m1 carbine. And this thing thrived in armies and raided from armories in bandit bands for over 60 years (production stopped in 1944, with 4 million produced, and I swear I saw a sawed off one in the hands of a phillipine guerilla on tv last year) It is arguably one of the most successful designs of all time, despite its drawbacks. –jjf

  7. The british actually stole the M16 action for their bullpup (SA80), it is slightly modified and they finally gave in and sent all of them to H&K to become the improved SA80A1 with short gas piston and some other minor mods to greatly improve reliability, shame they didnt come up with a simple way to convert from right to left handed (as in the french FAMAS) since lefties cant fire a right handed bullpup without brass hitting them square in the jaw every time they fire. The M16/M4 is a very light and very accurate weapon. But it fires a very underpowered round. The 6.5 Grendel and 6.8 SPC seem to be almost ideal cartridges given their vastly improved downrange power. The problems we in the military face are many; We have substandard body armor that weighs around 40lbs with all the extra plates and pads. For amost the exact same price we could go out and buy the 20lb dragonskin v2000 which still exceeds the protection levels we have now but increases mobility and maneuverability of the wearer. To keep your M4 in good condition in the sand you pretty much have to be OCD about cleaning it, im happy wih my SAW, much more reliable if you dont over lube it. SF gets the armor we need and the weapons we need because they can bypass the normal army beurocracy to buy what they need when they need it. the top generals are wearing dragonskin, but their men must make due with heavy and inadequate protection. These generals use privately contracted security, im assuming I couldnt do the job adequately. When was the last time you heard of a general getting killed by a roadside bomb or being shot over here? We need to change the way the military is run, we need better management.