Sal Fanelli On Mk. 318, M855, And Future USMC Small Arms Ammunition

SADJ has posted an excellent interview with Donald Roebling Award winner Sal Fanelli, a supervising engineer for Infantry Weapons Systems at MCSC. Fanelli commented on the creation of Mk. 318, its modification into the Mk. 318 Mod. 1 “Silver Bullet”, and even the potential for a new caliber for USMC rifles:

Why did the USMC decide they needed a new round of 5.56mm ammunition?

USMC determined that the performance of the M855 was inconsistent. Firing into a block of ballistic gelatin, we determined the M855 had yaw dependency. What we mean by that is from high speed videos of one round from an M4 we observed the path of the projectile doing exactly what we expected. It provided adequate terminal effects, but this didn’t happen every time. Other rounds went straight into the block and straight out of the block – no yaw, no enhanced terminal effects. We considered this inconsistent performance and confirmed that the M855 was impact yaw dependent.

We needed a round that gave consistent terminal effects from round to round, ammo lot to ammo lot and gave the exact terminal effects every time. We needed this performance at ranges from 0 to 400m.

Interestingly, while Fanelli does not give a reason for the inconsistent performance, Major Glenn Dean, US Army, did present one in his paper Small Caliber Lethality co-written with David LaFontaine.

Fanelli also commented on the possibility of the USMC seeking a round intermediate between 5.56mm and 7.62mm:

We did have an ulterior motive. There was a pending requirement for a new intermediate caliber. If we could improve the consistency of the terminal effects of our current 5.56mm round and use it as a temporary solution, it would bridge the gap until we could get the requirement going for an intermediate caliber. The intermediate caliber requirement remains in the discussion phase. Instead, our development resulted in a round that equaled the performance of the current 6.8mm round. Remember the Belgian SS-109 ammunition? It was selected as the NATO standard in the U.S., and was designated the M855? Well, that ammunition outperformed the Vietnam era M193. In a similar way, our improvements have now given us a 5.56mm round that gives us the performance of the current 6.8mm round. Of course, with the same technology approach, we know today that we can get a better performing 6.8mm round and 7.62mm round than the NATO standard 7.62x51mm M80 Ball.

This is one of the few government sources referencing a requirement for an intermediate round between 5.56mm and 7.62mm that I have seen. Even so, as he says the requirement “remains in the discussion phase”.

The Mk. 318 Mod. 1, an improved, lead-free variation of the Mod. 0 round with a higher ballistic coefficient, is competing against the M855A1 round developed by the US Army, according to Fanelli:

The original round was adopted as Mk318 Mod 0. This is a copper jacketed, open tip match, 62 grain projectile. If you don’t know ammunition well enough you might confuse it with the Mk262 which is a 77 grain projectile. The Mk262 is an open tipped match round used by the Special Ops community. Since we were worried about confusion with the Mk262, we had to take another look at the color of the tip. Every color was taken except for solid silver so we decided to nickel plate the entire projectile. As we now jokingly say, “All Marines will have silver bullets.” That round hasn’t been fielded yet, and a potential production contract is in the future. I can just see the Marines out there polishing bullets.

There is some additional testing that needs to be done. The USMC has type classified, adopted, and issued the Mk318 Mod 0 as an interim solution until formal testing has been completed on the Army’s M855A1. The decision on which round (Mk 318 Mod 1 or M855A1) will be fielded will be made within a year.

He also provided one of the only pictures of the Mk. 318 Mod. 1 I’ve yet seen:


Nickeled for identification, the Mod. 1 bullet has somewhat predictably been dubbed the “Silver Bullet”.



Fanelli’s interview is one of the first major pieces of information about the USMC’s enigmatic rifle ammunition program. While the story of M855A1 is fairly well characterized, the requirements and research that led to Mk. 318 has not been.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Vitsuas

    … but… but… I thought there was nothing wrong with the 5.56 ammo… I thought it was all shot placement that mattered… I thought failure to drop bad guys was the soldier’s fault…

  • iksnilol

    Nickel plated bullets? Isn’t that really bad for the bore?

    • Steve Truffer

      When combined with cosmoline, yes, as you’re essentially creating a high pressure solder setup.

      • iksnilol

        Yeah, but isn’t nickel really hard? Especially when compared to copper or lead.

    • marathag

      Hopefully it was just shorthand for Nickel Silicon carbide plating

  • Nicks87

    I wonder how it compares to a 62 gr Barnes TSX projectile?

  • tony

    Chances are the Marines will adopt the M855A1 for logistics reasons.

    • Dave

      it’d use the currently existing army-marines supply train and the brass would like it because it’d be a single cartridge across the board for both services.

  • CommonSense23

    I have first hand experience with the 318 and it is absolutely amazing. Have got to see it used in control setting in live tissue labs, and about the closest thing to a controlled setting in combat, and it is nice having a round that bridges the gap between 255 and 262.

  • Lance

    Always supported Mk-318 over M-855A1 HP ammo has better performance and wounding powers. Portland Police had use 55gr TRU ammo and had good performance with in in defense against criminals. Never was impressed by 62gr ammo, made to shoot threw none existent Soviet body armor in the 80s never preformed as it was suppoasted to be in urban combat against jihadis. Troops who still used 55gr M-193 had much better kill ratio per hit. So the USMC going half way with a 62 gr HP got a good balance going.

    As for new rifle/caliber dont get your hopes up Mr. F! When went threw this 3 to 5 years ago NATO standarization and fact 6.8 and 6.5 ammo was too expensive made a modernized 5.56mm the only real sultuion to the problem I doubt after ICC bit the dust and the Army spending millions on there new M-855A1 round will make a new round possible for the next decade.

    • I typically fall in on the other side of the caliber debate, actually.

  • nobody

    >In a similar way, our improvements have now given us a 5.56mm round that
    gives us the performance of the current 6.8mm round. Of course, with
    the same technology approach, we know today that we can get a better
    performing 6.8mm round

    Huh, the first thing that popped into my mind was to attempt a .17-.19 caliber round that could perform similar to current 5.56, and when combined with the polymer cased ammunition that the LSAT uses (which leave the bullet as the heaviest part of the round) would push the weight savings over 50% when compared to current ammunition.

    • Jay

      yeah. that’s what they need. A .17 caliber round. Like the .22 they use now is not anemic enough.

  • john4637

    A bit off subject…..but is the Colonel in photo a qualified Marine marksman? First time I saw a Marine officer or any Marine for that matter in uniform, with ribbons displayed, and no shooting qualification badges, unless that Marine was unqualified with current rifle and pistol! Just curious!!

    • Shaun Yancey

      He has a combat action with V device, Purple Heart, and what looks to be a Bronze Star. He at least knows combat. Shooting badges aren’t worn in that uniform.

      • Matt

        Shaun, badges are worn with that uniform, just not all the time. Also, combat action ribbon does not get awarded with a “V”. That is a gold star, meaning he earned the combat action ribbon twice.

        • Shaun Yancey

          It’s been a while since I wore my service bravos and shooting badges just aren’t required unless command specifies. It’s all coming back to me. And glad it’s a star and not a V. Wasn’t sure if thing have changed. Thanks Matt for the walk down amnesia lane!

          • Matt

            Happy to help, brother! S/F

      • john4637

        Been some changes since I left the Corps 50+ years ago.

    • Matt

      You must not spend much time on a Marine Corps base. We very rarely wear badges with ribbons anymore unless you’re in service alphas or part of the Marine Corps shooting team.

      • john4637

        Been a lot of uniform changes since I left the Corps. 50+ years ago!

        • Matt

          Yes, sir, I am sure there has been.

  • Shaun Yancey

    Powder??? Current loads have a built-in copper fouling reducer, are insensitive to temperature extremes. Greatly deters copper fouling and contributes to longer periods of top accuracy with less barrel cleaning time. Nickel plating fouling reducer available or even developed?

  • Shaun Yancey

    New weight requires new twist rates too. New barrels for everyone I guess. I’m going to invest in a barrel manufacturer.

    • CommonSense23

      You know that the 1:7 twist handles this weight perfectly fine right.

    • Joshua

      Barrel twist is not related to weight but length. That is why M855A1 needs a 1:7 twist and why M856 needed a 1:7 twist. Both are sub 70gr bullets, but both are long bullets.

  • Shaun Yancey

    Didn’t realize that.

  • RealitiCzech

    This question might be stupid, but why develop a new round when the 77gr Mk262 job supposedly does things quite well indeed?

    • CommonSense23

      262 is expensive, and it’s terminal ballistics are not the same. And the 318 has far better capabilities thru barriers aren’t the same.

    • Mk. 262 is not yaw-independent. It suffers the same problem as M855.

  • Esh325

    My understanding is that the biggest reason for lethality issues with the 5.56 were because of the m885 and the gradually tightened rifle twists. If expanding bullets were legal and they went back to a rifle twist like 1/10 it would make a new round unnecessary I believe

    • The twist rate doesn’t really have anything to do with it. See the article I posted above on the fleet yaw problem.

      • Esh325

        In the book the worlds assault rifles by Gary Paul Johnson it actually mentions that the Belgian designers of ss109 went to a tighter twist rate partially because there were concerns that the m193 and 1/12 would produce very horrific wounds that might violate Geneva or Hague conventions. I can pull out the section of the book if you want

        • CommonSense23

          Does this book have interviews and actual sources for that. I have reason verbatim in military training manuals, seen curriculum in the service academys for what is a violation of rules of war, things, that turned out to be dead wrong. That came from misunderstanding that came from playing the telephone game.

      • Rob

        Nathaniel – I thought that a slower twist allowed a larger yaw orbit in flight and thus improved the chance that the bullet would not hit perfectly perpendicular and just poke a hole.

    • Alex Nicolin

      The twist rate of 1/7″ was adopted in order to stabilize tracer rounds like the M856, which are longer and less dense than the M855 because they contain a powder instead of lead in their bottom side. Gyroscopic stability factor is proportional to density and inversely proportional to bullet length (see simplified Greenhill’s formula). 1/9″ is sufficient to stabilize M855 in every climate and barrel length. 1/10″ just barely works with long barrels that increase the velocity, at normal temperatures. If shot from carbine barrels and it’s cold and dry outside, they will keyhole.

  • CavScout

    Are they retarded? That’s the point of 855! Penetration. That’s why the core has a steel tip. To prevent yaw. For when you want to shoot doors, through people I guess, glass, light cover, unarmored vehicles, etc.
    If you want yaw again, that’s what the M193 did… DUH.