GMS-710 is a very unusual non-lethal submachine gun developed in the mid-’90s by a Russian company called Iceberg. This gun uses gas cartridges which shoot/spray a cloud of CS gas and are meant to be a close range non-lethal solution.
The gun does have a barrel, but instead of a conventional chamber, it has a block of split chambers. Three rows of eight cartridges (total of 24 rounds) are located vertically inside the receiver, pointing up. The second half of the chamber block is attached to the barrel and is located inside the upper receiver. In order to load the gun, the shooter needs to pivot the upper receiver, load the cartridges into the fixed half of the chamber block inside the lower receiver, then close the upper receiver thus connecting two halves of the chamber block. Upon firing the CS gas travels up from the vertically placed cartridges then goes forward into the bore.
The GMS-710 has an electrical primer ignition system which works in conjunction with proprietary non-lethal cartridges. The ignition control system is located behind the chamber block. On the rear wall of the receiver, there are switches controlling the rate of fire, fire mode selection and there is also a round counter showing the remaining amount of unfired ammunition. The whole system is powered by a 9-volt battery located inside the grip.
GMS-710 had no stock. Despite the very short effective range of gas cartridges’ and the lack of projectiles per se, they still equipped the gun with a set of iron sights.
Some sources say that the maximum rate of fire was 800 rpm. I think for such a multi-chamber gun with an electrical primer ignition the rate of fire can be infinitely high depending on the frequency of electrical impulses sent to the primers. Theoretically, such gun can shoot all the cartridges simultaneously, but obviously, that is barely anything practical and can also cause pressure related issues.
Reportedly, such an unusual layout was chosen to prevent any possibility of illegal conversion of the GMS-710 into a lethal firearm. Normally, in blank/gas firing guns there is a metal bar inside the bore preventing it from firing anything but the blank cartridges and CS gas ones. Another solution is the misaligned chamber and bore. However, such firearms pretty often become illegally converted into lethal ones by replacing the barrel or doing other modifications. In case of GMS-710, such illegal conversion is virtually impossible or at least too troublesome.