New Ammo for British Troops: UK Develops More Effective 5.56mm and 7.62mm Ammunition

It’s not just the Yanks that are getting improved ammunition: Our friends across the pond have developed their own firepower upgrade for 5.56mm and 7.62mm weapons alike. Jane’s has a modest article on the subject, while The Register provides a quite good overview of exactly what the new rounds are and what they mean for today’s Tommy:

The two new designs of cartridge, known as the Enhanced Performance (EP) round in 5.56mm and the High Performance (HP) round in 7.62mm, feature new – and, in the HP’s case, heavier – bullets. In addition, the HP round switches from single-base propellant powder to double-base, to give the heavier bullet the same flight characteristics as the old one. The EP also discards the age-old NATO SS109 bullet design, which incorporates a steel tip in front of a lead core, for an all-steel bullet, cased in the same gilding metal jacket as before. Its profile is similar, though.

BAE Systems’ new 5.56mm Enhanced Performance round, also known as the L31A1

The biggest change for the 5.56mm round is the switch from a two-part bullet, made up originally of a steel tip and a lead core, to an all-steel bullet. While it continues to have a gilding metal jacket (an alloy of 95 per cent copper and five per cent zinc), the departure from the standard SS109 bullet design is relatively radical.

Simon Parker, a project manager at BAE Systems Radway Green, spoke to The Register about the new rounds and the decisions behind the changes in their makeup.

“We wanted to see if we could improve performance against hardened targets. Having a solid hardened steel core improves performance above that of the steel tipped round,” he said. The new 5.56mm round, which will be known as the L31A1 in British service, retains a bullet weight of 62 grains (4g), meaning its ballistic performance will be very similar – an important similarity for soldiers firing it down their SA80 rifles.

For the 7.62mm round, known as the L59A1 in British service, the biggest change is to the weight of the bullet, from 144 grains (9.3g) to 155gr (10g). This increased maximum weight allows the new bullet to incorporate a steel tip, similar to the 5.56mm NATO SS109 design, giving it more mass with which to punch through a light target. Graphs from BAE claim that the HP bullet can penetrate an 8mm steel sheet out to about 400m, whereas its predecessor could only manage it at half that distance.


The British Army’s new L31A1 5.56mm round, sectioned to show off its solid hardened steel core. Image credit: Anthony G. Williams.


These new developments from the Isles come on the heels of multiple American improved performance loads for the two calibers, including the US Army’s 5.56mm M855A1 and 7.62mm M80A1 Enhanced Performance Rounds, and the US SOCOM and USMC’s 5.56mm Mk. 318 and 7.62mm Mk. 319 Special Operations Science and Technology rounds. The Australians, too, have introduced their own improved load, the 5.56mm F1A1, which features a much more modest redesign of the projectile from the NATO-standard SS109 round. All of these rounds sport improved propellants derived from the much more thermally-stable design created by St. Marks Powder, Inc, a Florida-based  subsidiary of General Dynamics.

The primary difference between the US developments and those abroad is how the configuration of the jacket is interpreted in the context of international law. American military legal counsel holds that a reverse drawn jacket does not constitute “incisions” or “piercings” that would violate the Hague Convention, while British and Commonwealth opinion tends to be that a traditional front-to-back drawn full metal jacket envelope is necessary for true Hague compliance.

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


  • Riot

    The MOD actually did something that considered ammunition, I’m surprised, pleasantly surprised.

    • Kivaari

      They were looking to punch holes in steel, and steel pokes better holes. The Brits used aluminum 110 years ago in the Mk VII. Brits used both fiber and aluminum, and the Italians used aluminum in 7.35mm WW2 ammunition. They did that, not for increased penetration, but for increased tumbling.

  • Major Tom

    Why Berdan primer? That stuff eats barrels and chambers. Even the vaunted 7.62x54R is getting rid of it.

    • Anonymoose

      I too find that quite odd. You would have thought they would have gotten rid of it when they adopted the 7.62×51. Was .303 back then even Berdan-primed?

      • FarmerB

        Seems like (I haven’t done an extensive survey) that ammo for most modern armies is Boxer primed in 5.56, but still Berdan in 7.62.

        • Ken

          The Swedish Carl Gustav made 5.56 that was available two or three years ago surplus from the Norwegian military (the non-lead primer made soldiers sick with other heavy metals and hydrogen cyanide) was Boxer primed. That was good for trolling brass vultures at public ranges (the kind that take your brass without asking and before you even know it).

          • squareWave

            I have a case of that Carl Gustaf ammo but haven’t used any of it yet. It also has a reputation for pierced and popped primers. Evidently the problem was the all steel core being harder than lead, which caused the copper jacket to resist the rifling more than a conventional projectile, which in turn resulted in copper vapors in indoor training environments. The Norwegian soldiers were experiencing metal fume fever, also common with industrial welders.

            I wonder if these other copper jacketed steel bullets will have similar issues.

          • Ken

            It’s also a really long bullet, longer than a 77gr even. That will result in high pressures, especially when trying to push it as fast as regular SS109.

          • Kivaari

            The trade off is it is using new powders and is only 62 grains win weight. I suspect that there is no increase in pressure at all, not even compared to the SS109 load it is replacing. We have seen dozens of new powder isn the last 80 years. Keep in mind that IMR (Improved Military Rifle) powder is now 80 years old. We’ve come a long ways since then.
            I suspect that before long there will be a powder that will lower the pressure in the M855A1 to a more reasonable level without sacrificing velocity. Either that or they will simply accept the increased wear on the rifles.

          • jcitizen

            Plus, maybe the twist rate of the barrel rifling may help – not sure though.

          • Kivaari

            I suspect the Brits are using the same 1:7 twist rate that we do. That way the new load should be every bit as stable as the existing load.

          • jcitizen

            Well, that is what all my buddies are buying, because they wan’t to use the M855, and hopefully the M855-A1 later, as we all prefer military surplus ammunition, and will even pay a slight premium for it, because of the packaging standards.

          • jcitizen

            You would think it would be cheaper to use soft steel jackets, but I suppose it is still desirable to resist corrosion, from storage.

      • Baggy270

        It was

    • Nebelwerfer

      Modern Berdan primers don’t ruin the barrels/chambers any more than regular Boxer primers, but the old corrosive stuff does indeed rust out your barrel. Steel cased Russian/Soviet milsurp. ammo often uses corrosive primers, even if produced way later than the 1950s (when most western countries switched to non-corrosive primers).

      Unfortunately, Berdan primers are still quite common in some European ammunition brands (e.g. RUAG and MEN LE/military ammo). Some claim that Berdans give a more even ignition due to the two flash holes, and are more tolerant to excessive pressure, but I (and all other reloaders) hate the effing things. The whole concept should have been scrapped ages ago.

      • Ken

        Berdan primers are a lot cheaper to make than Boxer primers since there isn’t a separate anvil to have to not only make, but also install in the primer cup. In a country that has been making Berdan primers for military use for over a century, it makes sense to stick with it. In addition, the two flash holes of Berdan brass are supposed to increase reliability in case one of the punches breaks or wears out on the cartridge casing stamping machine. I’ve seen postwar Czech 8×57 with only one flash hole before, and it still went off fine. I’ve heard of German WWII 8×57 sometimes only having one flash hole too. In both cases, they were probably running the equipment until it wore out, and then some. I’ve also seen Boxer primed ammo with no flash hole, which of course did not ignite. One was actually a round of American Eagle 9mm just last year, the other was a round of Greek .30/06 dated 1980.

        I suppose reloading Berdan primers isn’t a huge deal if you have a ready supply of them. While imported Berdan primers are reasonably priced in the US, you basically can’t find them. They seem to get imported once every few years and are sold out instantly. I know a lot of European shooters do it. They mostly decap with a water piston.

        • Kivaari

          Forty years ago 7.62x39mm ammunition was quite uncommon and I could only find Lapua brass cased Berdan primed ammunition. After finding special reloading tools from RCBS and several thousand FREE Norma 5mm primers I did all I could to capture that “unreloadable brass”. Once the spent primer was pulled from the case, using the bench mounted RCBS tool and then a custom made shell holder the new primers seated easier than Boxer primers. Yes, it was extra work but the results were well worth the effort. We grouse at having to pay $0.30 to $0.40 cents per round for AK ammo today and I was spending $0.33 per round over 35 years ago. reloading was an economical route to go even though Berdan primers were needed.
          The gun store where I got those several thousand Berdan primers simply was happy to give them to me as I was the only customer they ever had for them after they had sat on a shelf for over a decade.

      • UKShuggy

        It’s a little ironic when you consider that Colonel Berdan was an American, whereas Colonel Boxer was a Brit.

    • squareWave

      It’s not the primer type that causes chamber and barrel problems, it’s the chemical compound used in the primer. Non-corrosive priming compound can be used in Berdan primers just as readily as in Boxer primers. Lots of European ammo still uses Berdan.

    • Ed

      I don’t know why they list a berdan primer. Most UK surplus 5.56mm ammo I’ve encountered was boxer primed.

      • Kivaari

        Look at the images as they show Boxer primers. There is a central flash hole in both images. The 5.56mm shows an anvil quite clearly.

    • Kivaari

      Berdan primers, if old stock corrosive, wont ruin a barrel if you simply clean the rifle. Just like corrosive boxer primers in use by the US well through WW2 (except for the .30 carbine) would chew up barrels if the rifles were not cleaned. As a kid in the 60s we fired thousnads of round of corrosive ammunition. After learning what corrosive primers were at the expense of an Argentine Mauser rifle, I never had a problem again. Even after shooting thousands of rounds of corrosive 7.62x39mm, I learned that water is a really cheap bore cleaning solution. Even with non-corrosive ammunition I often clean using water. The key is to dry the weapon once the bore is flushed and then use common and inexpensive gun oil. I have not had a problem since the early 60s.

  • FarmerB

    Waiting for the hate to come down on the move to double-based powder for the 7.62.

    • RocketScientist

      Oooooooh, is this a piece of firearms drama I’m not familiar with? Are their conflicting and strong opinions on double-based powder? Are people going to get way too invested and start name calling? I can;t wait!!

      • FarmerB

        “Barrel Burner”

        • Kivaari

          Perhaps the issue with the new powder is is doesn’t foul or burn barrels. We have seen dozens of new powders come and go over the last 80 years. I suspect that is why they switched to the new formula.

          • FarmerB

            Not sure if it “burns barrels” or not – but many claim it does because the NG burns hotter. Primary reason may be power – getting the same velocity in the 155gn as in the older 144gn – which double based powders are good at.

          • jcitizen

            Also possibly more stable at high chamber temperatures.

    • ostiariusalpha

      robble robble robble… temperature sensitive… robble robble robble!

  • Wolfgar

    The British at least had the good sense to keep one munition plant running unlike the French who have to outsource their munition needs.

  • LazyReader

    Lead, what a revolutionary material I’ve never heard of it

    • Nebelwerfer

      It’s a quite popular material. Some places (e.g. Flint, MI) they have even started distributing it through people’s faucets!

  • ostiariusalpha

    So, they dumped the SS109 bullet design for their 5.56mm weapons… and decided it was good enough for the 7.62mm ones?

    • DIR911911 .

      the steel part of the 7.62 probably weighs the same as the whole 5.56 bullet does, giving you the penetration with some lead left over for expansion/fragmentation.

  • 40mmCattleDog

    You get a new enhanced performance round, and YOU get a new enhanced performance round! EVERYONE GETS A NEW ENHANCED PERFORMANCE ROUND!!

  • gunsandrockets

    Yep, Enhanced Performance “ball” ammunition, now with a hardened-steel solid-core!

  • Ed

    Just hope the UK’s news round won’t have pressure and fowling issues like-855A1 round does.

    • Zachary marrs


    • ostiariusalpha

      With that longer shank on the bullet, it doesn’t look promising for either one.

      • Kivaari

        With powder switching and load adjustment, there is no reason it would suffer from over-pressure issues. Every lot is loaded to be within the mil-spec limits.

        • ostiariusalpha

          You can adjust the powder load to avoid issues, but joule for joule, a lighter bullet with a longer shank is a very inefficient design compared to what it replaced.

          • Kivaari

            Except in the 7.62 you will see greater wounding performance. The lightweight steel tip will encourage tumbling to a greater degree than a solid lead core. Much like the Mk VII .303 with the aluminum or fiber tip from 110 years ago. The 5.56mm if you notice is still a 62 gr. bullet so the longer bullet should sail just fine. Since the rifle twist rate is fast for the longer tracer loads the slightly longer 5.56mm bullet should do well.
            If the 7.62mm bullet uses a thin jacket like the FN load, which is thinner than the USA load, the wounding should already have been greater than the M80. Testing of the FN v. M80 showed the 0.05mm FN jacket v. 0.08mm US jacket to deliver bad wounds, well worse from a victims point of view.

          • ostiariusalpha

            That is all well and good, but there are better designs out there. If we compare M80A1 to M80, the lighter EPR bullet keeps the shank length under control by extending the ogive and boattail lengths instead.

          • Kivaari

            I just find it another approach to the same end. Both will kill. I’d like to see Nathaniel F. do a comparison if he can get enough data. I suspect the extended range performance wont be that much different. Guessing is the most aerodynamic bullet will get a few more meters of performance, but will it be enough to matter? I like the Brit round since it is rather conventional and uses cheaper materials. Until I see BG tests and some ballistics charts I can with hold judgement.

          • ostiariusalpha

            It is cheaper, but you get a lot of bang for your buck with the EPR bullet design.

          • FWIW: FN once offered a SS109-equivalent in 7.62mm NATO, designated the SS123.

  • This seems like a very Cold War projectile to apply to the GWOT.

    A hardened steel core is generally used against a military force wearing body armor, with penetration being far more important than wounding effect.

    But the only issue in the GWOT has been wounding effect, due to the Fleet Yaw Effect + high fragmentation velocity required for M855.

    At first glance this seems a step backwards even from M855- it does not appear to solve the Fleet Yaw Effect, and with the core being made entirely of hardened steel, it may not fragment at any velocity. That leaves tumbling, which is great in the 7n6, but this lacks much of the air pocket in the nose, so whether it rapidly tumbles is unknown.

    Meanwhile, in terms of it’s goal for enhanced penetration of steel, that also seems rather dated. Although it can punch through quite a bit of steel, current hard armor is made of ceramics – Russia is fielding ceramics, and China has an entire industrial ceramics industry capable of pumping out low cost Level IV rifle plates – you can buy them on Alibaba for less than $200 a pair. That will either require Tungsten, some novel new super alloy, DU, or magnum rifle rounds such as .300 win and above.

    This really only seems optimal for fighting steel drones and robots.

    • Tom

      “This really only seems optimal for fighting steel drones and robots.”

      You know the British MoD has a satellite called Skynet. So until we get the plasma rifles into the forty watt range this will have to do in case it all goes horrible wrong.

      • Actionable Mango

        40 watts? Like the light bulb in an E-Z Bake Oven?

    • FarmerB

      Lead-free man, Green, ROHS, made with windmills, recycled, carbon neutral, etc etc

      • There’s no reason lead free has to be less effective; the M855A1 being a fantastic example. An OTM with a copper sintered frangible core would also have worked fine, and would likely have a very low fragmentation velocity, greatly extending range.

        • FarmerB

          I don’t agree. Density matters. Can you design something effective with most materials? Sure (depending on how one defines ‘effective’). But with less dense material, it’s harder and you give something else up in the compromise.
          But (esp in some parts of the world) they see lead-free as being more important than any other characteristic of the ammunition – including wounding/killing power. In fact, some countries changed the design of the SS109 since they considered it “inhumane”.

          • Some of the most effective rounds out there are lead free – Barnes TSX, M855A1, Lehigh Controlled Chaos, 7N6 (not technically lead free, but mostly). In the case of the TSX, it’s available all the way to 70gr’s.

            So at least for 5.56, unless shooting 77gr SMK’s is essential, really nothing is lost by going lead free so long as the bullet is well designed.

            As far as density goes, Tungsten is 1.7 times denser then lead 😉

          • FarmerB

            The most effective rounds out there? Sorry, that’s a wildly far-fetched claim (I load the TTSX for hunters, but…) and the jury still hasn’t been empanelled on the 855A1 yet (and I remember the first time around when it was claimed the 855 was wonderful).

            But you don’t address the short comings. Yes, you can have a 70 gn copper projectile in 5.56 instead of a lead 69 gn SMK (say). But it’s 1.036″ long and the Sierra is 0.9″ – how do you deal with that in an AR?

            Tungsten density – absolutely, pity it’s so hard to work and pricey.
            Disclaimer: I work with a bullet producer in Europe on very large copper alloy solids for extreme long-range shooting, so I’m not anti-Cu per say.

          • The 70gr TSX is loaded in 5.56 and shot out of AR’s, so clearly the length is not prohibitive.

            Have you seen the gel tests of the M855A1 and M80A1? They’re very impressive, as is the data sheet and backstory on them from the DTIC.

            Lead Free rounds really don’t seem to be giving up much if anything in terms of wounding, while also offering superior barrier penetration.

          • FarmerB

            No length is not prohibitive – but you lost .1″ of powder column. That has consequences, esp. for a military setting. Now, you need to reformulate your powder – a smaller charge of a faster burning powder. So gas port pressure changes. Pressure increases. Wear increases. The bullet is much more expensive (lead is ridiculously simple to work and form) and difficult to form (and it’s much harder and tougher on the barrel).
            Yes, I saw all the tests – but I remember the same blah, blah 40 years ago from the same organizations. I’m waiting to see how it works in the real world.

          • majorrod

            M855A1 has been in use for going on six years. How long does it take to put a jury together in Europe?

            The feedback from the field is outstanding. It is delivering on increased lethality.

    • John

      >This really only seems optimal for fighting steel drones and robots.

      Which should give you some indication of what future wars are gonna be like.

      • Right, but even at the most ambitious level, masses of ground based killer drones working together/independently of infantry are a decade out in terms of logistics and production time. And it’s hard to imagine 5.56 steel core being all that decisive against an ATV drone with a GPMG on top.

        Meanwhile, the GWOT is still very much in effect, and enhanced wounding effect is still required much more then penetration.

        • Kivaari

          That new 7.62mm round will be a good performer, since it will tumble quite well.

          • It’s basically a larger version of the SS109/M855, which was shown to have inconsistent tumbling depth due to the “flee yaw effect.”

            Essentially depending on the bullets wobble in flight, it can either tumble 2-3″ into the penetration as it was designed to, or as late as 8-9″. In the case of the latter, the result is a complete through-n-through against the thin, combat age males.

          • Kivaari

            If you notice it seems to be a larger, proportionally larger, than an SS109 style insert. It appears larger like the MK VII, and that was a good performing round. The larger plug will give two advantages, larger penentrator and larger and lighter in relationship to the lead core, so it should go end over end reliably. These two rounds need to be tested in BG to give us a good comparison.

    • Kivaari

      Did you know that Cold War ammunition puts holes in the lesser GWOT targets just fine. With all the trouble in Eruope it just makes sense to add better armor defeating technology into use. Sooner or later that third world fighting force wont be wearing pajamas to fight in, as armor will continue to be found in greater number. How much ANA and ANP body armor has fallen into enemy hands?

      • Well putting holes is the problem – when the rounds either fail to fragment, or yaw too late, then that’s all they do – poke a hole. Ideally they should be tearing/shredding, not poking.

        We’re fighting very thin, low body fat men, and that non-fragmenting / late tumbling performance results in through-n-through’s that have resulted in 5.56 being viewed as an unreliable stopper.

        Body armor is the future, and rounds absolutely should be developed for that.

        But these rounds (barring being of an unusual tungsten-like steel alloy) are not “Armor Piercing” in any modern sense, as they are designed to pierce steel, and body armor is not made out of steel, it’s made out of ceramics. Level IV Ceramic plates are actually cheaper to produce and purchase then steel plates now (check out Alibaba.)

        Based on Armor testing of the M855A1 and M80A1, steel cores can defeat steel plate, but cannot defeat ceramics. The only ceramic defeat I found was when a M2 black tip was fired out of a .300 Win Mag at 25 yards.

        So what you have is the worst of both worlds – the suboptimal wounding of an AP bullet, without being AP against actual body armor.

        • David Harmon

          AR 680/AR500.

          Take a step back from the problem. This solves something the governments are more worried about. Dissidents in reaction to their current behavior of letting these animals in. Remember the government invited these savages to live there. Not the people. The people are very obviously mad about it.

          • AR 680/ AR 500 is popular in the US, but it’s not nearly as much the case in the rest of the world. Nor do most of the locals have armor in their closets.

            If they were going to buy armor in preparation for some sort of uprising, they could just order it from Alixpress / Alibaba. There are Norinco and other defense industry manufacturers there who ship Level IV ceramic plates worldwide for around $200-$300 for front + back plates.

            Honestly the most plausible explanation is that they wanted a lead free round that was as cheap as possible to produce while offering some gain in performance, and was fully in line with the Hague’s limitations. The only problem is they picked enhanced penetration instead on enhanced soft target performance.

          • David Harmon

            You’re not thinking far enough out. If a civil war starts in the US, the UN will be called in. The UK will be the primary forces for the UN to take the lead to assist the government forces.

          • So the UK is switching to steel core in order to prepare their 153,000 man force to re-take the colonies along with a coalition of blue hatted troopers, with the goal of countering the threat of budget minded preppers wearing AR500 plates.

            Sounds legit.

          • David Harmon

            Far more plausible than trying to assume a military cares about lead in their projectiles.

            Militaries plan for the worse scenarios.

          • majorrod

            You’re ignoring the improved soft tissue performance.

          • Does the new steel core 5.56 offer improved soft tissue performance? And if so, through what mechanism (fragmentation, rapid tumbling, yaw independent, etc.)

            Because at least from that diagram, there’s nothing to indicate why it would be more effective then standard M855/SS109, and might actually less so, as hardened steel is less likely to fragment. Nor does it show any mechanism for solving the “Fleet Yaw” problem that created the unreliable performance of 5.56 in the first place,

          • majorrod

            Sorry, I wasn’t clear. I was referring to M855A1. It has actually devastating performance against soft tissue vs. the “suboptimal wounding” you characterized it of having.

            BTW, who in official channels is characterizing M855A1 as AP? They do make a big deal about its superior penetration capability because the bad guys do hide behind things that include thin skinned steel barriers/vehicles and cinder block. One round of M855A1 will penetrate cinder block, something M855 won’t do.

    • James Young

      Well, someone should be prepared for the robot issue when it arises

    • David Harmon

      Seems like it would also be pretty good at fighting against civilians with cheap access to body armor as well.

  • Vitor Roma

    The US went lighter with the 7.62 (130gr), UK went on the opposite direction (155gr). It would be fun to see a compariso between the two.

    • Kivaari

      I suspect they wanted the sights to remain pretty much the same calibration.

  • Kelly Jackson

    They should just get some of those exploding AR15 bullets Michael Moore was yammering on about last month

  • Kivaari

    The primer illustrated is not Berdan but Boxer. If you notice there is a central flash hole and an anvil in the sectioned case of the 5.56mm. The image of the 7.62mm also shows a central flash hole.

  • georgeIIII

    I would like to order 5 cases please !

  • Warren Ellis

    Any idea on how these two rounds compare to the M80A1 & M855A1?

  • GNTownsend

    May I point out that it is totally unnecessary for US ammunition manufacturers and the US Dept. of Defense to comply with the Hague Accords. The US Senate never ratified that treaty, so the USA is not bound whatsoever to its tenets. Why don’t we just field the best battle ammo on Earth and free our troops from the stupid rules of engagement which hamstring their effectiveness???

    • jcitizen

      That would horrify the greenie weenies, because they can’t stomach the slightest spot of lead upon their worshiped earth. I’ve read US directives for the new ammunition guide lines that literally stated that was the main trust for going non lead in the new bullets. Thankfully the developers took penetration and bullet yaw into perspective while obeying this ridiculous rule.

    • majorrod

      What many seem to forget is a spontaneous announcement that we will not follow the international standard opens up our troops to legal prosecution the world over.

      Working against us is we have adhered to the convention for a century. Yes, according to our constitution we don’t have to honor that treaty. The world doesn’t follow our constitution. BTW, there are a slew of other treaties that are unratified that we follow. (Look at nukes) The world of unintended consequences is real.

  • Arathar

    Wow seem to completly suck compared to the A1 EPR construction…