.40 QSPR Smoothbore


I think this is a rare cartridge!
I added this cartridge to my collection…

info from world.guns.ru/handguns/hg213-e.htm

Smith & Wesson Model 29 revolver modified by AAI corporation into Quiet Special Purpose Revolver (QSPR)
Image is a photoshopped modification of the original S&W M29 revolver photo to closely represent extremely rare QSPR weapon, © 2008 Maxim Popenker

Quiet Special Purpose Revolver (QSPR; also known as ‘tunnel revolver’ or ‘tunnel gun’) evolved from 1967 US Army requirements for a silenced, multi-projectile hand weapon for use by ‘tunnel exploration personnel’ (so called ‘tunnel rats’), which operated against Vietnamese communist forces in the numerous tunnels dug by NVA and VC personnel. The weapon concept was developed at US Army Land Warfare Laboratory at Aberdeen Proving Ground, in collaboration with AAI corporation, which was responsible for creation of the internally silenced ammunition, based on the “gas seal piston” concept (similar concept at the time was employed in a number of Soviet Spetsnaz weapons, firing PZ type internally silenced ammunition). The whole concept of the internally silenced ammunition is rather old and starts in the pre-WW1 era, but practical results were achieved only during 1950s and 1960s, when chemical and metallurgical technologies finally permitted manufacture of actual ammunition.
Quiet Special Purpose Revolvers (QSPR) were based on commercially available Smith & Wesson Model 29 .44 Magnum revolvers, rebuilt by AAI to handle their special integrally silenced ammunition. Earliest prototypes featured new, very short smoothbore barrels with .40" / 10mm bore, and with cylinder chambers reamed to accept QSPR ammunition which externally represented metal cased .410 gauge shotgun shells. Internally, however, the QSPR ammunition was quite different; it had a machined steel case with screw-in base. Primers were secured deeply in the cartridge base by screw-in bushing and additional anvil, which transferred the blow of the hammer to the primer (cartridges produced for tests in 1971 had no intermediate anvils). The small charge of gun powder was enclosed at the front and sides by the cup-shaped steel piston, which, upon discharge, was securely jammed at the mouth of the case by the internal thread. The QSPR ammunition fired fifteen tungsten balls (loaded into plastic sabot), each weighting about 7.5 grain / 0.5 gram, at muzzle velocity of about 730 fps / 222 m/s, which resulted in total muzzle energy of about 135 ft-lbs / 185 Joules. Due to the nature of the round (tungsten shot), the practical lethal range was estimated at about 30 feet / 10 meters, which was sufficient for extremely cramped tunnels of Vietnam war. The sound signature of QSPR round fired from QSPR revolver was about 110 dB, or similar to that of traditionally silenced .22LR pistol. It must be noted that QSPR revolvers had no sights, as these were intended for use at point-blank ranges and in very low visibility conditions of tunnels. The basic mechanism (double action trigger and swung-out cylinedr) were retained from standard S&W revolvers, although there were some modifications done to the hammer, and new short smoothbore barrel was installed.

First ten specimen of QSPR revolvers were delivered for field testing in Vietnam in mid-1969. Testing continued until late 1969, with several live fire encounters with NVA / VC personnel. It is interesting that most of these encounters were actually not in the tunnels but during the ambushes made by US special operation forces on NVA or VC trails. The field testing proved extreme usefulness of the QSPR revolver but also identified a number of issues which required further improvement of both the gun and the ammunition. QSPR improvement and testing program was initiated in 1970, and lasted through 1971. However, withdrawal of US forces in Vietnam caused the decline of interest in this and some other developments, and the QSPR program was quietly terminated in around 1972. Total number of QSPR revolvers built is not known, and various sources estimate that number between 25 and 250 guns in total.
Compared to the contemporary Soviet equipment of the similar nature, such as S4M silent pistol, the QSPR most probably provided somewhat more firepower at point-blank ranges (because of the higher muzzle velocity and bigger ammunition capacity), but it was also significantly heavier and bulkier. This is not surprising, as these guns filled different niches, the S4M being primarily a concealed-carry “spy gun”, while QSPR was a holster-carry “short range ambush” weapon.
2008 Maxim Popenker

Great photos, and quite a fingerprint in photo #2 - wonder if Interpol could make an I.D. from it? :-)

The US Army Limited Warfare Laboratory report “Quiet, Special-Purpose Revolver (QSPR) Design Improvements” can be found here:


Is yours .40 or .44?

I hope that revolver really is a photoshop creation. I’d hate to think they chopped up 4-screw Model 29s to make the QSPR.


Very cool cartridge there Gyrojet!

For what it’s worth, if I’d known this thread was coming up I would’ve taken a close-up shot. An original revolver was on display at the Army Ordnance Museum at Aberdeen Proving Ground in Maryland. It’s in the upper right of the display just below the Liberator. No cartridges for it to be seen. I might have a better picture available as my friend’s youngster took many more pictures with his camera.

Can’t tell what vintage the 29 is. Sorry Ray.


Jonny .44

In reading an article at this link on the QSPR, towards the end of it the author claims that the shot in the cartridge were made of Depleted Uranium. I hadn’t heard this before… Not correct?


No, Matt, I believe they were tungsten, but they could have been other things. Also, I have a question. In the Ammo Encyclopedia 5th Edition, it says that each cartridge qualifies as a suppressor and must be registered with the ATFE. Is this true? If so, is it the same with the Soviet silent rounds?

Also, this line got me (from the article Matt posted):

“It was the missing Vietnam gun, which was used in a homicide in California and recovered, according to Dockery.”

What could they have shot out of it? .44 Magnum? I don’t think it would have been an original round. I don’t even think many would have a round. I know some of us collector guys are desperate for some of the rarer ones, but not that much.

Somebody should inform them about the one mentioned in this thread too. It says in the article that the one there is the only live round in existence. Maybe not?

Loaded cartridges of that type are a problem in the US, fired are apparently OK.

Thank you jonnyc. I don’t think that verdict is honest though. A suppressor does thread on to the end of the barrel, but this does none of that. How could the ammunition be a suppressor?

“Silenced cartridges” like some captive piston designs are considered self-contained suppressors, and since the QSPR is such a rd, it falls under an ATF Technology Branch interpretation as such. I, and presumably everyone had thought the shot load was tungsten or steel, but the author’s authoritative claim that it was “in fact depleted uranium” in a rather revelatory tone, gave me pause enough to ask. Dick Fraser or a few others might know, but one should always ask here as Fede might materialize a top-secret document / patent or two with the answer, or Paul might post a sectioned photo with metallurgical details.

There are probably a dozen or fewer live ones out there, but the QSPR’s usually seen are the fired ones with the pusher all the way to the case mouth.

Matt, the shot pellets are made of Mallory, which is a trade name for a tungsten heavy alloy. The most typical variations combine ≥90% of tungsten with copper, nickel or iron, sometimes combined. The Army Concept Team in Vietnam report also mentions “steel pellets”, but this is not a very technical source and could be incorrect.

The WeaponsMan article also says: "The round has a dark finish which appears to be some kind of high-tech proto-melonite coating, although most resources describe the ammo as “blued”. Actually, it is a dull black chrome plating.



Thanks Fede. “Mallory” was the term evading me.

These can not be deactivated by simply drilling a hole in the case according to an employee of AAI at the time. They will detonate, no way around it. Only way is to fire them, and even then it has to be in a proper firearm.

Pete, do you know if it’s possible to move the piston back to its starting position?

Hi Jon
no I don’t. Sorry
look for an e-mail

For those interested in the Model 29 QSPR gun you might want to get a copy of Chuck Odom’s informative article entitled “The Mysterious ‘Tunnel Weapon’ of Vietnam”. It was published in the Spring 2014 issue of the Smith & Wesson Collectors Association Journal. Chuck noted that the ammunition can for this ammunition was lined in 1/4 inch lead plate in the event that a round was accidentally discharged within the container.

[Photo credit C. Odom]


I understand the notion of stronger packaging since, unlike any other typical ammo, this stuff is sort of built into its own barrel which concentrates the energy in one direction as far as possibly shooting though the can if it caught on fire. But why lead? A fire hot enough to set the ammo off might melt the lead, and a thin sheet of steel would seem to function just as well and not weigh as much.