7.92x57mm FN Armor Piercing Core


7.92x57mm steel core and jacket, greenish blue colored tip, headstamp FN/ upside down U/ 38
Don’t know anything on this! I love it when a primer hole is left.


Not a “U” but a Greek Pi (P in Roman), meaning penetrating;
Since Greece adopted 7,9mm in 1930, from FN, by acquiring 7,9mm FN M30 Mausers, and some 7.9 MGs ( Polish-converted French CSRG 15 done in the 20s to 7,9mm), the AP would have been part of the ammo contract.

Doc AV
AV Ballistics.


It might be helpful to identify the cartridge correctly. This is an Armor Piercing load, not just a “Steel Core”. Steel core can and often is used to describe a ball cartridge with a mild steel core as well. If someone were to use the search feature of this forum, they might not get a good or accurate result.

You should try to orient the flash holes in the case before you section it. The finished product is much better when both Berdan flash holes are visible. I learned this myself through trial and error since I was self-taught, well before I ever encountered this amazing forum.



That flash hole is a tough one, it all depends on case markings, headstamps, bullet size after cutting. On the M993, you have FFV on one side, take that off and its just a regular case, regarless of flash holes.
The Armour Piercing thing, well I’ve been corrected to many times to list. Not all steel cores are AP, and AP does not always have steel cores. To me anything with steel core that makes it a better penetrator is AP, but thats not true. Most will say it has a mild steel core, like a coat hanger metal. This will not penetrate steel as well as say tungsten ceramic carbide(M993). It would all come down to a hardness test on the steel to determine how much carbon is in the it, combined with what other metals that are mixed with it, like mangnanese, etc… to see if it has been hardened to a certain level. Could be as low as .25% for structral steel, or 1-2% in the ultra high strenght like knives and punches.
Now when the term for armour piercing was first used for bullets was during WW1 when British and Germans were sniping in the trenches. They were tring to defeat the sniper sheilds that the men were hiding behind. Not highly hardened armour steel plate, just steel plates. This was the British Mark V11S in 1915. The technology was just not there yet to make the hardened armor.
So, I just don’t know enough to be able to call it AP. To some it is, others its not! Thanks for bringing this up AKMS maybe we can take some kind of poll to see what everyone thinks in todays day and age.


In my opinion, you should not try to determine the purpose of the cartridge just by the hardness or performance of the steel core. The intent of the manufacturer and associated markings / color codes will tell you what it is. I have sectioned a number of steel core ball 7.62x39mm projectiles and found that most are similar in hardness. One Chinese specimen was notably harder, but still mild steel. All are still ball cartridges. From my own personal experience testing steel core projectiles against mild steel plate, the steel core did very little to improve the performance of the projectile compared to a similar lead core projectile. Certainly nothing about it would put it anywhere close to the “armor piercing” category.



I agree with AKMS. In fact, this applies to Pistol ammunition as well, and the constant referral to mild-steel cores in pistol ammunition as AP has led to laws governing importation and possession of ammunition that is ordinary ball, and performs no different than ordinary ball, but has been put on the “AP” list simply due to having mild-steel cores. In most cases, these rounds were never officially designated as AP ammunition by the countries and companies making them, and the mild-steel cores were simply done to preserve the supply of lead for other strategic purposes.

Aside from even that, we have ranges in our area (indoor types) that do not allow the use of any ammunition with a projectile that will attract a magnet, for fear it will punch their slanted steel backstops, which most of them will not. the do not diffrentiate between hardened and mild-steel cores, or even between a steel core and a steel bullet jacket over a lead core.

It doesn’t help the hobby to constantly use and publish wrong designations in these instances, especially for those of us who live in restrictive states.

John Moss


As a continuation of this thread, and because it is important for us shooters, are german 7,9 S.m.K. bullets considered AP or “just” improved penetration? Since they also made an S.m.K.H bullet, the AP designation would belong here* and not to the S.m.K.

*And to the rare tungsten bullet.


S.m.K. are considered armor piercing, as denoted by the red primer seal.

John Moss