Army and Weapons | Deadly Quiet Special Purpose Revolver (QSPR) | Quiet Special Purpose Revolver (QSPR, also known as 'tunnel gun' or 'tunnel gun ") evolved from a 1967 U.S. Army requirements for a silent, multi-projectile based weapons for use by' tunnel exploration personnel '(called' tunnel rats'), which was active against the Vietnamese communist forces in the many tunnels dug by NVA and VC personnel. The gun concept was developed at the U.S. Army Land Warfare Laboratory, Aberdeen Proving Ground, in collaboration with AAI Corporation, responsible for the establishment of internal silence ammunition, based on the "gas piston seal" concept (similar concept at that time worked in a number of Soviet Spetsnaz weapons, ammunition shooting PZ sort of internal silence). The whole concept of the internal silenced ammo is quite old and starting in the pre-WW1 era, but concrete results were achieved only during the years 1950 and 1960, when the chemical and metallurgical technology finally allowed the production of real ammunition.

Quiet Special Purpose Revolver (QSPR) were based on commercially available Smith & Wesson Model 29 .44 Magnum revolvers, rebuilt by AAI their special integrally silenced ammunition to handle. Earliest prototypes new very short smooth-bore, equipped with 0.40 "/ 10mm bore and cylinder chambers reamed to QSPR ammunition represented externally metal cased .410 gauge shotgun shells Internally, the QSPR ammunition was very different to accept. Had an edited steel case with screw-in base. Primers were deep down put in the cartridge base by screw-in socket and additional anvil, the bang of the gavel over to the primer (cartridges manufactured for the tests in 1971 had no intervening anvils). The small amount of gunpowder was enclosed on the front and sides of the cup-shaped steel piston, which dismissal was safe at the mouth of the case was stalled by the internal thread.

The QSPR ammunition fired fifteen tungsten balls (loaded in plastic sabot), each weighing about 7.5 grain / 0.5 grams, at muzzle velocity of about 730 fps / 222 m / s, resulting in total muzzle energy of about 135 ft-lbs / 185 Joules. The nature of the round (tungsten shot), was mortally practical range is estimated at about 30 meters / 10 meters, which was sufficient for extremely narrow tunnels of the Vietnam War. The sound signature of QSPR round fired from QSPR revolver was about 110 dB, or similar to those traditionally silenced .22 LR pistol. It should be noted that no sites had QSPR revolvers because they were intended for use at point-blank ranges and very low visibility in the tunnels. The basic mechanism (double action trigger and swung out cylinedr) were maintaining the standard S & W revolvers, although there were some changes made to the hammer, and the new short smooth barrel was installed.

First ten copies of QSPR revolvers were delivered for field testing in Vietnam in the middle of 1969. Testing continued until the end of 1969, with several live-fire encounters with NVA / VC personnel. It is interesting that most of these encounters actually not in the tunnels, but during the ambushes of U.S. special operations forces NVA and VC paths. The field tests showed extreme usefulness of the QSPR revolver, but also a number of issues that a further improvement of both the gun and ammo. QSPR improvement and testing program was started in 1970, and lasted until 1971. However, withdrawal of American troops in Vietnam caused the decline in interest in this and several other developments, and the program was quietly discontinued QSPR around 1972. Total QSPR revolvers built is unknown, and various sources estimate that number between 25 and 250 guns in total.