9x39mm Russian
        New in the USA in 2018: (Per Wikipedia, not me)
The 9x39mm is based on the Russian 7.62×39 mm round, but with an
expanded neck to accommodate a 9 mm (.356 caliber) bullet.
The cartridge was beginning to be designed in the 1940s by a team of a
supposed 27 unknown members, but was later finished by N. Zabelin,
L. Dvoryaninova and Y. Frolov of the TsNIITochMash in the 1980s.
The intent was to create a subsonic cartridge for suppressed firearms
for special forces units that had more power, range and penetration
than handgun and some rifle cartridges.
The 5.45×39 mm cartridge introduced in 1974 for the AK-74 lacks
sufficient bullet weight (at 53 gr to 80 gr) for acceptable energy at
subsonic velocities.
The bullet of the 9×39 mm is approximately 16 g (250 gr), double that
of the normal 123 gr 7.62×39 mm round, and is subsonic.
This slow velocity does not produce a sonic boom, but does limit the
muzzle energy and effective range of a weapon when compared to non-
suppressed rifles.
The round has an effective lethal range of 400 to 530 meters and a
maximum penetration of up to 10 mm of steel. Like the 5.45×39mm
cartridge, 9×39mm SP-5 features an airpocket in the tip, which
improves its capability to yaw after impact, and thus increase its effect
on soft tissue.
The 9x39mm cartridge and some of it’s weapons are currently being
banned in some war zones due to the unethical and “overpowered”
nature of the round. There is a bill being put in place named “The
Vladikavkaz 9x39mm Subsonic Round Restriction Certificate“ and is
unknown if it will continue to stay in effect. Not much is known of this
Military, Police & Sporting Cartridges