Modern Personal Defense Weapon Calibers 010: The 9x19mm and 9x21mm Russian Special AP

Left to right: 9x19mm ball, 9x21mm 7N28 ball, 9x21mm 7N29 AP, 9x21mm 7BTZ AP-T, 9x21mm SP-12 JHP. Image courtesy of Maxim Popenker

One potential solution to the problem of a suitable anti-armor pistol and submachine gun round is to take the existing ammunition system and introduce one or more new kinds of ammunition which provide additional armor piercing capability through higher muzzle velocity and tougher core material. This is the route taken in Russia, where in the mid-1990s was introduced several loads for the Western 9x19mm caliber, as well as a new but fairly conventional round, the 9x21mm, also with optional AP load.

Left to right: 9x18mm ball, 9x19mm ball, 9x19mm 7N21, 9x19mm 7N30, 9x19mm 7N31, 9x19mm FN experimental sabot round. Image courtesy of Maxim Popenker.


Three major steel-cored AP loads exist: In the 9x19mm, there is the 7N21, launching an 82gr bullet at a little over 1,500 ft/s. Also in 9x19mm, the 7N31, which launches a 65gr bullet at nearly 2,000 ft/s. In 9x21mm, the 7N29 which loads a 103gr bullet at about 1,350 ft/s. These three loads give us a very convenient cross-section of the ballistic possibilities for full-caliber 9mm AP rounds, so let’s take a look at how they perform:

Because of their lightweight bullets, these rounds also weigh less than standard 9mm. 9x19mm 7N21 AP weighs 9.3 grams per shot, the 7N31 8.3 grams, and the 9x21mm 7N29 weighs 11 grams.

The primary advantage of these AP loads is their low round weight relative to regular 9x19mm, good ammunition size and characteristics for use with pistols, relative to 5.7x28mm and 4.6x30mm, and backwards-compatibility with existing platforms, which also allows the use of proven JHP projectiles for use against soft targets.

The primary downsides are poor energy retention vs. 9mm ball, and poor armor piercing capability beyond 50m versus the 5.7x28mm and similar rounds. Recoil, as we’ll see later, sits in-between 9mm ball and 5.7x28mm. Therefore, I feel that this sort of ammunition should only be considered if armor-piercing capability is needed primarily in the pistol and machine pistol, and not if the round is also intended to defeat armor at ranges beyond 50m when used with carbines and submachine guns.


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


  • @nathaniel_f:disqus Is there any information on the material of the steel penetrators? I’ve always wanted to know how they manufacture the penetrating core via lathe or MIM/Sintering?

    • Giolli Joker

      I would be surprised if they were to cast or sinter such a simple shape.
      Given the size they could probably simply cold form it out of a rod/wire but I’m just guessing.

    • Flounder

      No military in the world is going to use either of those methods for bullet production. Those are small time machine shop or small batch production methods. Giolli probably has it right with the penetrator being formed from a steel wire that is cold worked into shape. At least I know some steel bullets are formed that way.

      • roguetechie

        That’s not even close to true. But thanks for playing

    • Maxim Popenker

      IIRC those cores are stamped and then heat-treated to proper hardness

      • roguetechie

        Thanks Max!

        I’ve been fascinated with SJ-ESC and other exotic handgun ammo since I saw the section you had about it on your site at one point

    • Kevin Gross

      Believe that they are Tungsten Carbide cores, and they are sintered with a nickel/ iron binder.

  • Giolli Joker

    Will we see also the 6.5CBJ?

    • 6.5 CBJ, yes. 7 Penna, maybe.

      • noob

        Has 22 tcm 9r been done?

      • mig1nc

        I searched the site, but didn’t find 9×39. If you haven’t done that one yet, any plans to?

        • I might throw it into MPDWC or MIC. It’s sort of an oddball round, not really intermediate and not really a PDW round, either. MPDWC won’t be the last series of these I do, however.

  • Edeco

    Generally I believe in straight walled pistol cartridges, even for AP; more tail cross section to soak up energy off of the propellant gas molecules inside the barrel hole.

    All else being equal though esp. pressure and bullet weight, I think a narrower bore/projectile will give less peak recoil. So if absolutely trying to squeeze out a little more ME at a given level of controllability, bottlenecks could still make sense. Maybe.