Marines and the XM8

Corps shouldn’t jump gun with weapons

My vacation continues, but I’ve got limited net access and I noticed this opinion-type article in Marine Corps Times about the Marines’ decision to stick with the M16 for the time being. That decision was noted on MO back in March. At the time I wondered what the specific reasons were, and I said that if the Marines were not jumping onto the XM8 bandwagon, that was good enough for me. This latest piece is an op-ed, not a specific press release, but the writer seems to be thinking along the same lines as MO and a large percentage of MO readers.

History is replete with instances of the Marine Corps jumping the gun (pardon the pun) and going with an untried weapon system. Perhaps the most stinging was the 1967 adoption of the M16.

The M14, which the Marines had at the time, proved to be a valuable asset to the Marine rifleman because of the rifle’s durability, functionality and power. Then the Corps decided to forgo the tried-and-true Garand action for the new ‘lighter-weight’ M16. The results of choosing this untested, black plastic ‘Mattel’ rifle were disastrous. Many Marines died at the hands of this rifle, due to the lack of a forward assist. If the weapon jammed, it had to be disassembled, cleaned and lubricated, often under fire.

It also should be known that the M14 was deemed “too heavy” for the average infantryman. An unloaded M14 weighs about 9 pounds. The original M16 was in the neighborhood of 7 pounds. By contrast, today’s M16A4 weighs 8 pounds (without any accessories, mind you). You do the math. And today’s pack as fielded by the individual Marine is the heaviest ever — more than 100 pounds.

Fast-forward to Afghanistan in 2001. Many Special Forces troops chose the venerable M14 over the M16A2/A3, due to the 7.62mm round’s ability to reliably kill targets at longer ranges than the 5.56mm M16A2/A3. Additionally, the M14’s ability to shrug off dust storms and keep running engendered operator confidence.

The biggest drawback of the XM8? The 5.56 round.

One reason to wait is the need for a replacement round for the 5.56mm. Among the possibilities is the 6.8mm SPC round, which has generated much interest in the firearms community as a successor to the 5.56mm service round. It offers 7.62mm punch in a smaller package.

Another possible successor is the 6mm/.223 round. The 6mm/.223 loading is merely a 5.56mm (.223 Rem) case necked up to a 6mm. It uses a 100-grain bullet at approximately 2,600-2,700 feet per second and has a ballistic coefficient similar to a 7.62mm round. The 6mm is the right round for 7.62mm punch in a 5.56mm package.


Let’s face it, the 5.56mm, especially in the M855 (green tip) loading, is lackluster against targets past 100 and 150 meters for the M4 and M16, respectively. There are many instances of infantrymen engaging targets three and four times with the shorter-barreled M4s, whereas the M16 has a slightly lower incidence of follow-up hits to stop attackers.

The Corps should campaign for the XM8 in either a 6.8mm SPC or a 6mm/.223 chambering. A bonus to the 6mm/.223 is that the existing M16 family of weapons would require only a barrel change. The bolt and magazines remain compatible. As for the M249 squad automatic weapon, the links and bolt may be retained, again necessitating only a barrel change.

MO readers seem to prefer the 6.8 SPC, with a small but vocal core of 6.5 Grendel enthusiasts as well. I haven’t heard much about this 6mm/.223 round, and am looking forward to MO readers speaking out about it. The author of this Marine Corps Times article certainly seems to be a fan of it, so let’s hear some numbers and opinions from the MO gun nuts. (That’s you guys.)


  1. You mean the 6.5mm Grendel. I’ve done a couple of ACE posts on it. The shell is shorter, thus allowing a longer bullet with a better BC. This makes the 6.5 a better long range (300-1K meters) round than the 6.8. It’s a daughter of the 6mm and 6.5mm PPC rounds which have shined in 1K competitions for accuracy in punching small groups in paper. Some say the 6.8mm is a better short range round, and studies have shown only military snipers shoot at targets beyond 300m often. I’d ask why a round which is better at a long range would not be better at a short range. To have a lot of retained momentum at 1K yards, a round better have a lot at 300 yards, as non-self-propelled bullets sure don’t speed up. But, the slightly bigger, heavier bullet might have a bit more punch at short ranges. Some argue going with the 6.5 would allow grunts and snipers to use the same ammo, but snipers are probably going to use .300 WMs or stronger (.338 LMs or .50 BMGs) anyway. But, all that said, if we’re going to an entirely new rifle, there’s no reason to restrict the length of the cartridge to the current length of the 5.56mm anyway, so we could have a 6.8mm cartridge (with its slightly bigger caliber and larger case capacity) AND a longer, streamlined bullet with a longer effective range. If we elect to stay with existing AR lowers and just replace the uppers, then either the 6.8mm SPC or the 6.5 Grendel would be an improvement over the 5.56 with only a slight penalty in magazine capacity and ammo weight load. If we stay with the AR design, but buy new rifles, the ‘AR-47’ (AR frame chambered for 7.62x39mm) is an option. The magazine well has to be designed slightly differently to to AK magazines, due to their curvature. Knight’s Armament and others already have such firearms. One commenter on the ACE blog says reports on firearms forums don’t support the claimed 2800fps muzzle velocity for either factory loaded or hand-loaded 6.8mm rounds, so the claim that the 6.8mm SPC equals the 7.62 NATO round at short ranges may be hyped, as expected. Just as there’s no substitute for cubic inches in dragsters, there’s no substitute for case capacity in rifle rounds. If a better powder can be used in the 6.8, the same powder can make the 7.62 even more powerful. If the 6.8 SPC doesn’t have the claimed muzzle speed, we can discount all the other specs we’ve been reading. I’ve called for some firearm magazine to do a complete comparison of the 6.8 SPC, 6.5 Grendel, and 7.62×39 AK rounds using test barrels of carbine, general, and sniper length (roughly 12, 16, and 20 inches), with the twist optimized for each of the three rounds. Let’s see flight ballistics and terminal ballistics, using the same gel medium, metal plates, pot roasts, or what have you.

  2. ACE, I’m just guessing at what he meant but a better short-range cartridge might be one that has less recoil, allowing better control of the weapon in a CQC situation. I read somewhere that the SEALs switched from MP5 to custom short-barrelled M4s for CQC because they needed the more powerful round (too many bad guys have kevlar) while retaining a light weapon with controllable recoil. It has the added benefit of reducing training complexity because they switch to standard-barrelled M4s for their primary weapon. SEALs still like larger calibers when they have reach out and touch someone, though.

  3. I don’t see a complete test of the 6.8 vs 6.5 in the first article — just some numbers (right out of the manufacturer’s pages) thrown about. I’ve read the 6.8 is not achieving those numbers in reality. I’d like to see independent tests. I don’t see where the 2nd article says 5.56×45 is equal to 7.62×51. Besides, anything you can do to make a 5.56×45 better can make a 7.62×51 even better than that. Defense Review is enamored with the LeMas blended metal ‘smart’ bullet but gel tests by another expert have all but debunked it. Standard gel tests don’t look nearly as impressive as the LeMas ‘pot roast’ demos. The idea of a magic bullet which can penetrate hard stuff but expands and does not penetrate soft stuff is hard to believe. I’ve read the report that the troops like the results, but I’d still like to see some comparison test data, from controlled tests. The comment in one of the two articles that a bullet manufactured with a hole in the center works better tickles me. The old fashioned name for that is a hollow point. Yes, I’ve seen that it’s a deep hole of a small diameter, but the effect on impact is essentially the same. I know it’s claimed to be part of the manufacturing process and thus not in violation of the Hague convention (something we never agreed to, anyway). We need to quit playing games and just declare we will use hollow points on combatants which don’t fight for a state-supported military. An optimized hollow point would make the 5.56mm a much better man-stopping round, if it turns out we’re stuck with it for another decade or more.

  4. That’s a very useful chart, Sam. Now that I see it, I seem to remember seeing it before. I’ll have to study it. I’d still like to see a gun mag do an independent study comparing all those rounds, however. Wish I had the resources to do it. (And the manufacturers would loan me the firearms, like they do the mags.)

  5. ACE: Yes, I meant 6.5 Grendel, not 6.8. D’oh. Fixed now. Thanks. Still on vacation, so didn’t get to check comments until now. But as I expected, MO readers are on top of the issue. You guys rock.

  6. Murdock, you might want to look at how your commnents are linking when you get home. I clicked on the comments under your Election Projection post and got the comments for the Marines and the XM8 post. I was going to comment that Chris Matthews ‘Horserace’ page shows a much tighter EV race. The Harris and Pew polls also show a very tight race. As long as Bush doesn’t really choke on the first debate (like Ford did with his Poland comment), I’m thinking we’ll see a solid 8-10 pt. lead the next week. Heard a Pundit say the key question is whether most viewers like Kerry more or less afterwards. I can’t see him looking like somebody most Americans would like, even if he were a good actor. Dick Morris said Kerry abandoned his right flank in taking a position that he’d find a way to withdraw US troops beginning in 3 months (replacing them with French and German troops – yeah riiight). 30% of his ‘base’ thinks we should stay in Iraq until we prevail, now that we are there. Sensing this, he’s since said he too wants to win there, sitting on the fence. Kerry has already pulled ads from 4 battleground states, while he’s spending lots of time in Ohio (his quagmire), trying to keep it blue. Florida, a state he needs, appears to be leaning red. Even states which were considered strong blue states, like NJ, are breakeven now. If Kerry comes across in the debates as the same ole stoggy, condescending, humorless, long-winded, incoherent, waffling, fence-sitting liberal; the floodgates will open, and many Dems (including the Blacks he’s pretty much taken for granted) will just stay home on Election Day. Gore got 11% more of the women’s vote, but the terrorists give Bush a big boost (through no intent of their own) with the atrocity in Russia. ‘Security moms’ are thinking Bush is more likely to keep anything like that from ever happening to their children. If the Aghan elections go anywhere close to well (and the 82nd is there to insure they will), that will be a huge PLUS for Bush. By inference, Americans will see every Iraqi will eventually be able to vote without fear of his/her life. The Dems may start fighting amongst themselves down the stretch, as they realize even the lawyers will not be able to send this election into OT. But, like Yogi said, it’s not over til its over. World events beyond the control of either candidate could tilt the scales either way. Bush is not perfect in my book. He’s gained lots of votes by moving closer to the big government philosophy of the Dems. But, my right-wing libertarian views would not appeal to even 25% of Americans.

  7. As a marine soon to be sent over to Iraq, I think that the brass should really consider adopting SOMETING NEW!! I have heard stories about 5 or 6 rounds of standard 5.56 being pumped into a bad guy and he still kept coming. I want to come home safe and serve my country and take down the badguys with a single round. Why the hell are we using such a weak round in the first place! We are the United States Marine Corps, we should have the biggest baddest metal flying at our disposal, not pea shooters! However I do have a question about the Grendal and others, are they tumblers? Like our M16 Ammo? Or what is their deal for stopping power? Thanks. Semper Fi

  8. Another series of posts with very good points being made all around. Anyone who’s read my other posts about the XM8/5.56 combo is aware I’m a proponent of further ‘real world’ testing of RBCD blended metal ammunition (distributed by Lemas). ACE (who I agree with about 99% of the time) is correct that reports of inferior performance of RBCD in test gelatin need to be investigated further. There has been some resistance by the military establishment (who oddly enough seems to have their own program they’d like to forward) to using RBCD. The only honest way to settle this issue once and for all is to stage a large scale test of RBCD by troops in the field (I’m sure there would be plenty in the Stan or Iraq who’d like the chance). People who’s lives depend on gear and weapons working properly aren’t going to be concerned about hurting the manufacturer’s chances of further sales, or of putting the lie to hinky claims by their services acquisition/ testing organizations; which sometimes have their own programs or agendas to further. If the troops in the field say RBCD has ‘minor’ problems, let’s give the manufacturer a chance to fix it, and if the troops say it’s junk let’s forget about it. The big attraction (for me)to this potential boon to our troops is the positive rap it’s received three years in a row at the Armed Forces Journal invitational shoot off. The testers are almost entirely active duty or recently retired Spec Ops personnel and/or senior firearms evaluators who know their weapons and ammo. The tests of RBCD against hard and soft armor, and against soft tissue BEHIND the soft armor are quite convincing. The AFJ testers have to no vested interest, that I can see, in touting the effectiveness of this ammunition. Additionally, I’ve read two annectodotal reports from former Spec Ops personnel, who’ve gone to the ‘independent contractor’ market, who’ve used RBCD under field conditions. Both reported stellar performance of RBCD against bad guys (it sucks to be them!). While two unconfirmed reports is hardly conclusive-it supports what the AFJ testers have said for three years in a row, and supports the advisability of large field tests by our troops. We should not give them an improved firearm without the improved ammo it and THEY deserve! God bless our troops!

  9. ***Quoted from: Field Report: Marine Corps Systems Command Liaison Team, Central Iraq USMC 20-25 April 2003 [MSWord 110 Kb], Page 5, 2nd header*** 5.56mm vs. 7.62 Lethality ~ 5.56mm ‘definitely answered the mail’and ‘as long as the shots were in the head or chest they went down’were typical quotes from several Marines; many who were previously very skeptical of 5.56mm ammunition. Most of the interviewed Marines who reported targets not going down and/or could still fight were referencing non-lethal shots to the extremities. There were reports of targets receiving shots in the vitals and not going down. These stories need not be described, but are of the rare superhuman occurrences that defy logic and caliber of round. Some Marines did ask about getting the heaver-grained 5.56mm rounds, up to 77 grain if possible. ***************************************

  10. I was just reading up onn the French FAMAS bullpup rifle (not a chautchat), and I am thinking that a bullpup weapon compatible with certain parts of the xm-8 would be a good thing for the U.S. Marines. Use the 20′ DM/AR barrel, with the carbine’s (?) handgaurd(s), magazines, and the common scopes adn other accessories. Be sure to make the ejection port switchable for the lefties. This would make it a more or less all-in-wonder (mostly) and a reduction in the amount of stuff an MEU has to haul around; with the drawbacks of having an awkward change of magazines and consequent retraining. While not going with a bullpup was an initial requirement by the suits, the Marines might be more amenable to a bullpup variant than the Army, especially if the two are compatible. Thoughts?

  11. While nice to have such a compact rifle with a full legnth barrel, current bullpup designs all have a flaw which makes them rather unsuitable for MOUT (with the exception of FN’s F2000). When working on urban terrain, when you fire around a corner you want to present as little a target as possible for the enemy to shoot at. What usually happens is the you shoulder your weapon on the side that’s closest to the edge of the cover and then just poke out a bit of your head, shoulder, arms and weapon. When shooting on your strong side that works fine but due to the ever changing terrain of urban combat, if you have to switch shoulders on a bullpup you get a cheek full hot brass. On a conventional design there’s already a brass deflector so cross shoulder transition and firing isn’t much of an issue. Not that terrible a flaw everywhere else, since you’re going to be firing from your strong side almost all the time. I just realized something. If the XM-8 bolt was designed so that anyone trained on the AR15 bolt could disassemble it, does that mean they kept the extractor the same piss poor design?

  12. Murdock: If you would like a demonstration of the abilities of RBCD ammunition, I can arrange with test parameters suggested by you or anyone else. I am the Master Distributor for RBCD Performance Plus in Texas, Washington and Oregon. The RBCD ammunition gives operators primary weapon performance from a SECONDARY weapons platform.

  13. The Cobb Muli-Caliber-Rifle would be a better choice to replace the M16 and the M14. I can handle over 50 different calibers/cartridges. With the MCR, the military would not be locked in to one particular caliber.

  14. I think the most cost effective way for us to adopt a harder hitting cartridge would be to switch to the 6x45mm cartridge. It gives a good 200 yard advantage over the 5.56 and also penetrates much better. As for being tumblers – the 5.56 fired out of a 16′ barrel has no ‘tumble’ effect once it passes 100 to 150 meters, because it has less velocity – it merely zips through the target – leaving no real cavity or damage. The 6×45 will probably extend this range by a good bit, because of greate bullet weight and energy on target. The Grendel is the optimum IMO. Unfortunately, it will cause a major re-fit and top brass will never go for that. With the 6x45mm, only barrels will be replaced, since it already fits in all mags and bolts and links. Thus, you now have one cartridge instead of 2 (5.56 and 7.62Nato), because the GPMG’s can use said cartridge as well.