Stovepipe

"Stovepipe" is the common American term for rocket-propelled anti-tank recoilless rifles and guns - known as "Bazookas" in British English. These weapons are generally, but not exclusively, man-portable and are often - erroneously - referred to as Rocket Launchers. In fact, the weapons do not propel anything at all, but are mere firing tubes; the projectiles are propelled entirely by their own integral rocket motors.

Design Principles & Use
Stovepipes are generally, unlike their Russian RPG counterparts, recoilless rifles rather than recoilless guns. In other words, the tubes of these weapons have a grooved lining that imparts spin upon an accelerating projectile in the same manner as the barrel of a conventional firearm or cannon. They are "recoilless" because they are not a closed system, but a hollow tube that is open at both ends. The exhaust and propellant escape out the rear without imparting much monentum onto the launcher itself, but create a potentially-hazardous backblast. Generally, Stovepipes fire shaped-charge HEAT (High Explosive, Anti-Tank) warheads which, although extremely effective against even very thick armor, are generally not used in conventional cannon due to their unique properties. The power of such shaped-charge rounds is directly perportional to their diameter. The fat, blunt-nosed projectiles are ill-suited to being fired from a normal gun; even when propelled by a rocket, they are extremely un-aerodynamic and unlikely to fly straight. This makes Stovepipes innaccurate past a few hundred meters, but the raw hitting power of shaped charge warheads - combined with the extreme simplicity and light weight of the entire system - makes them unrivaled short-range anti-tank weapons for infantry.

90mm Recoilless Rifle M27A3 "Super-Stovepipe"
The M27A3 "Super-Stovepipe" is a 90mm / 3.5" man-portable, shoulder-fired Infantry anti-tank weapon that is issued to one man in each American infantry squad. The weapon system is 1.52 meters / 5 feet long overall and weighs right around 8 kg / 17.63 pounds empty. It is capable of piercing a maximum of 300mm of armor, sloped to 90 degrees, and has an effective range of approximately 300 meters against a stationary target or ~200 meters against a moving one. While it is possible to knock out enemy Armored Fighting Vehicles at longer ranges, because the penetration of shaped charge warheads is not affected by flight time, their limited accuracy means the Super-Stovepipe is of only limited utility at ranges greater than those stated above.

105mm Heavy Recoilless Rifle M42A2
The M42A2 is a more powerful recoilless rifle used by dedicated anti-tank troops in the Anti-tank Section of a Rifle Company. The weapon is man-portable and shoulder-fired but requires at least two, preferably three, soldiers to be properly used - the operator, loader and spotter, who work in concert much like the crew of an Armored Fighting Vehicle or cannon. The M42A2 is generally fired by the operator from a prone position using an integral bipod, but can also be utilized standing up, preferably by balancing the forward portion of the tube on the shoulder of the spotter while the loader inserts fresh projectiles. The M42A2 is accurate out to a range of about 500 meters against stationary Armored Fighting Vehicles, or about 350-400 meters against moving targets. Its main advantage over the more portable "Super-Stovepipe" its the accuracy increase afforded by its longer tube. It has been tested to penetrate up to 400mm of Rolled Homogenous Steel plating and is assumed to be able to go through more - this has never been tried, however, as it is presently capable of punching through the armor of any known vehicle up to and including the American M70 Heavy Assault Gun.