Russia's Burevestnik Institute, a subsidiary of Russia’s state-owned defense contractor UralVagonZavod (UVZ, famous as the designer of the T-72 and T-90 tanks), has commenced serial production of the 2B25 82mm 'Gull' mortar. This mortar produces little sound and no flash because each shell has a captive piston in its tail to contain the propelling charge gasses. Captive piston cartridges in 12 gauge and .38 Special were originally developed for and used by U.S. forces in Vietnam, but American interest faded when that war ended. The Russians developed an interest in the technology and the 2B25 mortar is their first captive piston weapon to reach serial production:

http://www.thedrive.com/the-war-zone...ppressed-rifle

Russian Commandos Are Getting "Silent" Mortars That Are As Quiet As A Suppressed Rifle
The weapons use special ammunition to eliminate smoke and flash during firing and keep noise to an absolute minimum.
Joseph Trevithick - September 7, 2018


Personnel at a forward operating base are patrolling the perimeter after dark when they hear a muffled popping sound in the distance. Soon after, small shells begin raining down on them and there’s no clear indication where the attackers are shooting from. They’ve just been on the receiving end of a 2B25 “silent” 82mm mortar.

This might sound like some sort of unlockable upgrade in a video game, but it’s an actual weapon system that Russian special operations forces, commonly referred to as spetsnaz, began receiving in 2018. Jane’s was first to learn that the Kremlin had begun fielding the specialized mortars from an unnamed individual at Russia’s Army 2018 defense exposition in August 2018.....

.....From the outside, the 30-pound mortar doesn't look out of the ordinary and it functions in the same way as many other modern types. An individual inserts the mortar bomb into the tube and then pulls a handle-shaped trigger to fire it. The shooter aims the weapon by using an optical sight and adjusting the angle of the barrel.

Where the 2B25 is special is in its 3VO35 82mm ammunition. A traditional mortar bomb has a propelling charge in its tail and troops can generally attach supplemental charges to increase its range. The detonation of these explosives forces the projectile out of the barrel and sends it down range.

The Gull’s mortar bombs keep that detonation entirely contained in the very long tail assembly. The sudden, extreme force pushes a physical piston against the base of the tube, which launches the projectile.

This means firing the 2B25 produces no flash or smoke and helps contain any residual auditory signature of firing behind the mortar bomb’s own body and the tube of the mortar itself. It’s not actually silent, but Burevestnik claims that shooting the weapon isn’t any louder than firing an AKM assault rifle with a PBS-1 sound suppressor attached, which is substantially quieter than a standard infantry mortar.

The 3VO35 mortar bomb features a high explosive projectile encased in a fragmentation layer made up of dozens of small steel balls, making it well suited to attacking troops, light vehicles, and ammunition and fuel caches out in the open. Regardless of the target set, being able to catch those targets unawares and giving them little warning to try and seek cover would only improve the 2B25’s effectiveness.....
Photographs and more text at the hyperlink, above.