The 7N1 bullet

I recently purchased some 7.62x54R ‘7N1’ ammunition and pulled a few bullets to sample them.
Here are the three I pulled, one whole, one partially sectioned, and one disassembled(lead core, steel core, and jacket).

I was surprised to find bullet construction of this type(small air pocket, then a short steel core on top of a lead core). I have always heard comparisons which lead me to believe that the 7N1 bullet was basically and enlarged copy the 7n6 bullet(with a rather long air pocket over a lead sleeve covering a steel core that extends to the base), while it actually appears to have more in common with the SS109 projectile. …Or perhaps, to some degree, even the FN P80 .30caliber AP projectile.
Maybe someone more knowledgeable can enlighten me about this bullet design and its origin/influences.
For instance, which projectile type was designed first, the 7N1, the P80, or the SS109?
Were the designs of either of the later two projectiles influenced by the one that was designed first?
Were any of them influenced by the composite core of the .303 MkVII bullet?

Two ideas pop to mind, both of which may be wrong. First, the Russian 5.45mm bullet has a steel core behind an air pocket and is designed to cause the bullet to tumble on entry.

The design of the steel core is interesting with the blunt tip and sharp corners. I remember some work done with aircraft unguided rockets designed to penetrate hardened concrete runways and buildings. The penetrator warhead had a blunt tip and sharp corners like this bullet core. The purpose was for an oblique impact, the corner of the warhead would catch turn the projectile into the target for better penetration. Frankly, I don’t remember if it actually worked, or if I ever saw firing results of oblique impacts. I can see where an air pocket ahead of this core could simplify impact dynamics.

Again, I offer this as a completely uninformed input.

Cheers, Lew

The 7N1 projectile got developed after it was found out that simple “LPS” projectiles manufactured as precise as possible were still not accurate enough due to the lead sleeve between the jacket and the core which was varying in thickness and caused more dispersion than wanted. So the designers had to shorten the core to get it out of the projectile section which was guided and compressed by the lands and fields.

Originally Finnish projectiles were evaluated because of their precision but the new sniper projectile had to have the weight of the regular 7.62x54R projectiles in order to be exchangeable in case no sniper cartridges were available. So the Finnish design could not be adopted since lighter projectiles were required.

The 7N1 got adopted in 1966 and the core is made of “Steel 10”.

The “new” sniper cartridge is the 7N14, adopted in 1999 and has a hardened core of “Steel U12A” what makes it into an AP. The internal construcion is basically same as 7N1 just the core has a different shape.