Linear

A linear launcher (also called an "inline") is a type of cannon in which the barrel is directly in front of, and pointing in the same direction, as the chamber. Such a configuration is slightly cheaper than the over/under configuration, but only by the cost of 2 90* elbows. The linear design is most often used in combustion launchers, and this is considered the most basic launcher design. It's also the simplest to assemble, requiring no special tools or fittings.

The linear design is often considered slightly more powerful than over-under configuration as the traveling gases don't have to make a 180* turn thus slowing the speed of them.

Most pneumatics are not linear because of there increased chamber length and piston valve arrangement.