The T27 "Xylophone" rocket launcher was designed during World War II. In October 1944, tactical uses for this weapon were developed by the 18th Field Artillery Battalion, First Army. The rocket launcher's concentrated firepower initially had a great demoralizing effect on the enemy. However, the T27 had limited range and was time-consuming to reload. Tests determined that the T27 was difficult to position for ground firing, so the T27E1 with a modified mount was developed.

8x1 4.5 Inch Rocket Launcher, T27

The T27E1 is one of 12 rocket launchers designed to fire the M8 self-propelled, fin-stabilized rocket. The T27 and T27E1 were all eight-tube designs, with the T27E2 having 24 tubes. Nicknamed the Xylophone because of its shape and design, the T27 was small enough to be carried in the back of a two-and-a-half ton truck. Despite its light weight, it was difficult to maneuver due to its elongated tubes. As a result a revision, designated the T27E1, was produced.

The T27E1 could be broken down into pieces for easier stowage. It was also easier to reposition on the battlefield, making it more lethal that the T27.
The rockets were first developed in 1941 and entered service in 1943, and were classified as barrage rockets, to be launched in large quantities. Over 2.5 million M8 rockets were produced between 1941 and 1944. Due to the M8's ineffectiveness in striking and damaging armored targets, it was retired before the end World War II, and replaced with the more improved spin-stabilized M16 rocket.

With the development of larger capacity rocket launchers, better rockets, and more accurate and lethal artillery weapons, the T27 was retired at the end of World War II. Other 4.5 inch launchers remained in service through the Vietnam War in a limited capacity.