10x26mm Stranian

Overview:
The 10x26mm is a powerful and versatile cartridge developed from the rimmed 10x30mmR cartridge used for decades by the Stranian Empire. With advances in self-loading firearms, experiments with downscaling the round into a semi-automatic cartridge were made, including 7.8x24mm, 10x10mm, and 6.5x16mm.

However all of these cartrides and firearms would be surpassed by Koltarov's design and the M1930 firing the 10x26mm autoloading cartridge. Soon replacing the 7.6x24mm cartridge in Stranian service at that time.

The 10mm cartridge is immensely powerful by semi-automatic standards. Firing an 80 grain projectile at 2400 feet per second (731 mps). Which earns the cartridge a reputation for a significant kick, but this only adds to the charm for many operators.

This power also manifests itself with it's ballistics and effect on targets. With the humble cartridge far outpreforming most other pistol cartridges in use, making it particularly effective with carbines and PDW weapons.

Design and preformance:

The most basic round is the 10P6 cartridge. Being a traditional lead core jacketed with copper-plated steel. An advancement was the 10P6M which uses techniques similar to 5.45x45mm 7N10 rounds. With a pocket of air near the tip and a hardened steel core surrounded by lead. This provides good penetration against armor and causes significant wounds against unarmored targets. But this comes at the cost of inferior preformance at range as the cavity produces a tendency to yaw at range.

The 10P6N armor-piercing cartridge is an advanced cartridge for defeating hard and soft body armors, while maintaining effect against unarmored targets.
The 10P6N utilizes a sub-caliber core contained within a steel plated lead sleeve. Seperated between the core and the rest of the projectile is a thin layer of  polyethylene.
If the bullet strikes an unarmored target, it holds together to produce a wide wound channel. If the bullet strikes an armored target, the sleeve is stripped away and the core penetrates alone.

Variants:
10P6N AP.
10P6M FMJ
10P6 FMJ.
SP-10 Subsonic.

Specifications:

Place of origin: Strania
In service:    1930–present
Designed: Late 1920s

Cartridge specifications:

Parent case: 10x30mmR
Case type: Rimless Straight
Bullet diameter: 10.20 mm
Neck diameter: 10.45 mm
Base diameter: 10.80 mm
Rim diameter: 10.80 mm
Rim thickness:   1.80 mm
Case length     26.40 mm
Overall length 36.00 mm

Case capacity: 2.00 ml (30 gr H2O)
Primer type Large pistol
Maximum pressure: 248 MPa (36,000 psi)

Ballistic performance:
Test barrel length: 116 mm (4.6 in).
-Bullet mass/type-                -Velocity-            -Energy-
80 gr  10P6 FMJ                731 m/s (2400 ft/s) 1387 J (1023 ft.lbf)
150 gr SP-10 subsonic            323 m/s (1060 ft/s)    829 J (611 ft.lbf)
84 gr  10P6N AP hardened steel core 731 m/s (2400 ft/s) 1457 J (1075 ft.lbf)


Here are some charts against real world rounds.
shooterscalculator.com/ballist…