Article Update Notification 11-25-2021: This article was originally published about a year ago. Recently (11-17-2021) CMMG announced the release of an AR style build chambered in 4.6x30mm. This has spiked a renewed interest in the 4.6x30mm and I have thus made some updates and edits to this page from when it was originally published.
If you spend a lot of time in the shooting world, you begin to get bored with the Vanilla. For example. it’s hard to get excited over an AR build, unless someone really does something that bucks the norm. The same can be true for ammunition, everything that is released, has been released in some form or fashion in the past.
It is for this reason I really do not get overly excited about new cartridges. I like to see what they have to offer, and do comparisons, but they have to offer something uniquely different then what is otherwise available for me to consider making the investment in a firearm and reloading equipment.
A duo of cartridges fit that bill for me, to where I will likely own a firearm chambered for one or both of these cartridges in the future. These are the Heckler and Koch’s 4.6x30mm and FN Herstal’s 5.7x28mm. There is an interesting backstory to both these cartridges, while most people have likely heard of the 5.7x28mm, comparatively few people know much if anything about the 4.6x30mm.
The Backstory
In the 1980’s the North Atlantic Treaty Organization more commonly refereed to a NATO, put out a request for a replacement to the 9×19 Parabellum. Much like the 45 ACP, this round had been developed in the early 19th century, using 19th Century technology. NATO felt that the 9×19 lacked in a few key categories, mainly the ballistics were not all that great, the ability to pierce armor was very limited, and the terminal ballistics of the ball ammunition was relatively poor. The organization put out the call to develop a replacement round.
It seems like there were few competing entries. Domestically, Colt introduced a 22 caliber cartridge that was more or less a shortened 223 Rem called the 5.56×30 MARS. MARS is short for Mini Assault Rifle System. Reportedly this cartridge would lob a 55 grain projectile a tad shy of 2,600fps. Despite a few patents being issued in 1998 the concept never made it beyond a few prototypes. FN, did take the challenge and developed the 5.7x28mm cartridge. While rumored to be based on the 30 Carbine necked down to 5.56 (.223) caliber, the reality is the case was a completely new case designed from scratch.
This new cartridge was introduced in the early 90’s as part of the the FN 5.7 Pistol, and the P90 Carbine weapon systems. The P90 and the FN 5.7 Pistol were designed to be companion guns, shooting the same ammunition. The Five-seveN Pistol (No joke that’s how it’s spelled) came standard with 20 round magazines while the P90 had 50 round magazines.
The 5.7×28 cartridge is more akin to a miniature rifle round then it is a straight wall pistol cartridge. The service pressure is 50,000psi, compared to the service pressure for 9×19 or 34,000psi. The projectile is light typically 40gr, compared to the 9mm’s 124 or 115gr projectile. This means in order to generate sufficient energy the bullet velocity needs to be high. The test barrel for the 5.7×28 is 10.3in, and a 40gr Hornady V-Max bullet is propelled to ~2000 fps imparting ~340ftlbs of energy.
In testing the 5.7x28mm performed better then the 9mm on armor penetration. These tests, performed on soft Kevlar body armor stopped the 9mm slug, but were defeated by the much higher velocity and smaller cross sectional area of the 5.56 caliber slug. The recoil was notably less, the 9mm pistols, allowing quicker and more accurate follow up shots. The ballistics of the 5.7×28 were more favorable as this round had a greater effective range then the 9mm.
For all of these reasons and a few more, the 5.7×28 was set to replace the 9×19 parabellum until the Germans got involved. Their entry of the 4.6x30mm came six years after the introduction of the 5.7x28mm. They had developed the MP-7 submachine gun to fire the round, and were working on a companion (H&K UCP) pistol, which to date, has never came to fruition.
The 4.6x30mm utilizes an .18 caliber bullet, and has a service pressure of ~58,000psi, and utilizes a 7in test barrel. The bullet weights range from 30gr (2.0g) to 41gr (2.7g) and have a reported muzzle velocity of ~2,350fps to ~2400fps depending on load.
Both the 4.6x30mm and the 5.7x28mm were tested and compared to the 9x19mm extensively. Not just by NATO, but also by NATO member states, including France, United States, and Germany. When all the dust was settled, the 5.7x28mm really shined, it was the superior round. However it was not adopted by NATO, Germany protested and refused to accept it.
Thus it seemed doomed until a certain TV show came along that forever memorialized the P90, and the 5.7×28 round….Stargate…..ok, maybe not, but that show introduced a lot of people, myself included to the P90, and the concept of Personnel Defense Weapons (PDW). Even had the aforementioned TV show not aired, the cartridge would have surely continued it’s slow but steady gain in market share since it’s introduction. While the conclusion of the NATO trials it was not clear as to what the future would hold for the 5.7x28mm or the 4.6x30mm this did not limit either round from enjoying limited success. Both cartridges have been adopted by agencies both in the United States, and abroad.
Because HK’s primary market has always been LEO and Military Contracts, the civilian market plays second fiddle, and there has not been much of a push to market the 4.6x30mm to the civilian market. Part of that has been because of the legalities restricting the MP7 given that no semi auto version has been offered by HK. For this reason the 4.6x30mm was almost exclusively used in H&K’s MP-7. However that has began to change as it can be found as an option for many European based bolt action firearms, and most recently (and notably) as in an AR platformed now being offered by CMMG in their FourSix.
There may some question as to what the 4.6x30mm might be useful for, personally I think it would be a pretty handy pest control cartridge. Likely exceeding the performance of the .17 Cal rimfire magnums, and likely coming close to many of the larger .17 Caliber centerfire offerings. There will be an write up in the near future looking at the ballistics of the 4.6x30mm to some of the other .17 caliber cartridges of prominence (yes, 4.6 is technically .18 caliber).
Unlike the 4.6×30 the 5.7×28 has been steadily gaining popularity and market share in the United States civilian market basically since it’s introduction. FN is caters more to the civilian market then it’s German Rival. 5.7x28mm AR Uppers are available through Atlantic Arms, that utilized standard P90 magazines. CMMG offers an AR build that uses modified AR Mags for the 5.7x28mm, and Ruger introduced a new 5.7x28mm pistol last year. Federal and Speer are currently producing 5.7x28mm ammunition for the civilian market, and it hasn’t even been adopted into SAAMI yet.
(To be fair, unless a cartridge is sponsored by a SAAMI Member company, it won’t be adopted, and here in the United States, companies are free to produced ammunition as they please without specific adherence to SAAMI guidlines unlike CIP Markets).
Why did the 5.7x28mm Win Out to the 4.6x30mm?
There are some logistical reasons as to why the 5.7x28mm made more sense then the 4.6x30mm. The first being, that the 5.7×28 has both a tested and somewhat proven weapons platform and H&K did not. They had the MP-7, but they did not have a companion pistol. In the six years between the launch of the 5.7x28mm and the 4.6x30mm, FN moved forward developing the infrastructure for the testing and production of it’s ammunition. There was virtually no support for the 4.6x30mm outside of Germany, and likely, outside of the H&K facilities.
There was also the logistics of manufacture. All of your major bullet manufacturers offer a .223 caliber bullet, and most in the 30 to 40 grain variety. This meant that it was far easier to source at least a capable bullet from any one manufacturer. Virtually no one makes a .18 cal bullet. There are many manufacturers of a .17 caliber, but .18 was a bit of an odd ball size. Manufacturers would need to tool up and develop bullets.
Both cartridges were ground up designs, which meant any new tooling to make brass would need to be developed from scratch. Sure their might be some interchangeability with existing production lines, with the 5.7x28mm being introduce 6 years prior manufactures interested in the contracts had already done the leg work.
Then there there was the performance. All of the aforementioned points could have been overcome if the 4.6x30mm was substantially better then the existing 5.7x28mm but the test results didn’t bear that out. This wasn’t as much a test between the P90 and the MP-7 but rather a test of the round itself.
We can take a look at a few basic metrics to see the merits of the 5.7x28mm and the 4.6x30mm.
As you can see from the charts you two very similar cartridges in terms of Muzzle Energy and Muzzle Velocity. The much slower, and much heavier 9x19mm wins out in muzzle energy, but has other limitations which will will discuss. Based on these metrics alone, it is very hard to determine which would be the better round, which is why some of the other logistical issues may have ultimately favored the 5.7x28mm over the 4.6x30mm.
If you came away thinking that the 9x19mm is looking like a clear winner you are likely not alone. Remember the data was taken from a 4in SAAMI Test barrel. The moment we start shooting this from a 8.5in MP-5 barrel length we are going to completely outclass the other two cartridges in all but a few metrics.
For all of it’s virtues, the 9x19mm is roughly ~25% heavier, and magazine capacities are limited when compared its potential predecessors. As mentioned before, it tends to produce more muzzle flip and recoil then the contending offerings. This becomes especially important during sustained automatic fire, something most civilians are not concerned about. The last big thing that cuts against 9x19mm is it’s inability to penetrate body armor, even when fired from a carbine.
These last few metrics hard hard to put hard numbers to, but there’s plenty of research out there talking about the 5.7×28’s ability to pierce Kevlar vest especially when loaded with rounds designed for the purpose. Sporting rounds, which are copper jacket/lead core have dismal performance against body armor, but their AP counterparts do a fairly good job.
As I mentioned the data between the 4.6×30 and the 5.7×28 is very similar, to the point where I’d call them virtual ballistic twins. Given that, there is no question why NATO and most of it’s member countries came to the conclusion that the 5.7x28mm was a more viable candidate to replace the 9x19mm as a NATO standard round. Had Germany not objected, we would likely have seen it happen in the early 2000’s.
Touching on Terminal Ballistics
We did not touch heavily on terminal ballistics, and while it played some role in the decision between the 4.6x30mm and the 5.7x28mm it is hard to draw a comparison between what NATO member states use and what we would use as civilians. Most military’s, including the United States, use ball ammunition, designed not to expand. In both the 4.6x30mm and the 5.7x30mm the ammunition was designed to tumble within the target. The tumbling action destroyed tissue and dissipated energy much like a hollow point, but less efficiently.
If we were to test these cartridges to civilian self defense standards we’d load them with premium expanding bullets. Given both cartridges and the 9x19mm have muzzle energies that are solidly within the “Pistol” category we honest would expect them to all perform very similarly. At which point we would be left with the argument that we’ve had for decades regarding the 45 ACP and the 9mm, is bigger better or is more better?
My sense is that bullet quality has become so good in the last 25 years that energy dissipation within a target is quite efficient. Animals, two legged or otherwise, are not going to notice a difference of 50 or 100 ftlbs of muzzle energy either way. The thing that seems to stop a bad guy from doing bad things, is how many shots are promptly and properly placed on target. With that said, there becomes merit to having a cartridge (and a firearm) that provides more opportunities for proper shot placement, and the reduced recoil/muzzle flip increases the odds of subsequent properly placed hits.
5.7x28mm vs Other Cartridges
While we focused on mainly the 9mm vs 5.7x28mm vs 4.6x30mm they are not the only high velocity small caliber pistol rounds out there. It is also not a new idea, the 8.5mm (.334) cal Mars was a cartridge developed for the Mars semiautomatic pistol in the lat 1800’s. It produced a screaming (for a semi auto pistol) 1750fps and people reported it being quite unpleasant to shoot. It was a limited production firearm that never saw widespread adoption or success.
There are also examples like the 7.62×25 Tokarev, 22 TCM, and the .22WMR some of which have been around for near a century. All more or less trying to make a light bullet, go really fast. It may be warranted to take a closer look at the 5.7x28mm and compared it the likes of the 22 TCM, or perhaps the 357 Sig, but neither of these cartridges seem to be gaining market share like the 5.7×28 is.
Concluding Thoughts.
Both cartridges are tricky to reload for, as they can be particularly sensitive to variations in charge weight and cartridge overall length (COAL). In the case of the 4.6x30mm it is difficult to find components and ammunition. Since the MP-7 is only sold to LEO and Military contracts, and .18 cal is an atypical bullet caliber, you are kind of stuck, unless you know someone with an “in”.
If you are like me, and have big meat hooks for fingers, I am sure you’ll find the .18 cal bullets rather unpleasant to pick up and try to seat. Probably slightly better then .17 cal, but only slightly.
The 5.7x28mm has it’s own challenges, as it has a fine layer of lacquer applied to the outside of the case to aid in feeding. Any sort of abrasive tumbling will remove the lacquer and will cause feeding issues. Most people will try and rinse the cases in a mixture of mild soap with warm water in order to preserve the coating. The small shoulder, and the thin brass at the case mouth can cause issues if things aren’t lined up perfectly when loading.
There is no such coating on the 4.6x30mm cases. It is not needed as the case has a proper taper, unlike the straight walled 5.7x28mm. Sources of 4.6x30mm brass and loaded ammo can be hard to find at times, but supply is likely to be better given CMMG’s introduction of the FourSix.
This is all to say, if you are new to hand loading or reloading in general, these are not the cartridges to learn on. However I believe either cartridge would likely make a for a somewhat splendid little varmint cartridge. I would need to run the numbers, but I envision a small little SBR bolt action with a 10.5in barrel….a light handy little thing. Would it it be better then any other cartridge out there designed for varmints? No, but I could have the rifle and my pistol chambered for the same round, and there’s something neat about that.
If the 4.6x30mm was ever to take off, I suspect we will see a flood of “Micro” wildcats being developed. The obvious one would be to neck it down to .17 caliber. However why stop there? Why not answer the question “How low can you go?”. That’s a topic for another day.