Railgun

Railguns are electromagnetic projectile devices which use electromagnetic means to accelerate solid materials. Such weapons are used as artillery weapons by vessels in the Tau'ri fleet. A standard magazine will carry ten thousand rounds, capable of delivering shots at a velocity of mach 5 at a distance of 250 miles. They have become standard on the F-302, BC-303, and 304 series for ship to ship combat, and a few shots will be able to take out a Wraith dart relatively quickly, though Ori shields are significantly more difficult to pierce.

Behind the scenes
In reality, the technology exists to build railguns; however, it is difficult to obtain sufficient power for them to be effective and to get the barrel of the gun in question to withstand the extreme temperatures and speeds of the projectile, wearing out the barrel with only a few uses. Presumably, the fictional explanation for the ability to make operational railguns would be the invention of the Naquadah generator and the discovery of more durable materials, such as Trinium.