Taper Bore Gun

The concept is simple, by narrowing the caliber of the weapon gradually from the breech to the muzzle, a much higher pressure is built up behind the shell, and as it speeds down the barrel it is reduced in diameter. Some of these guns reduced caliber by as much as 1/3 as the shell traveled down the barrel. This resulted in a higher muzzle velocity, and a much more dangerous projectile.

For example, during the war, Germany produced two types of 75mm anti-tank guns. The conventional weapon was capable of defeating 135mm of steel armor at 1,000 yards, using a special tungsten shell. The Taper Bore version of the same weapon was capable of defeating 175mm at the same range.

As well as creating a more effective gun, the design of Taper Bore weapons resulted in much lighter weapons, making the transport and deployment of these guns faster and easier.

Because the materials needed to manufacture the guns to tolerate the friction and wear of firing were so rare in Germany by the end of the war, very few of these guns were made. The ones that did make it into combat proved their effectiveness until being surpassed by cheap weapons like the Panzerschreck, and recoilless rifle.