Talk:M4/@comment-89.99.143.205-20160707214405

The M4A1 carbine is a fully automatic variant of the basic M4 carbine intended for special operations use. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group, while the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group.

https://en.wikipedia.org/wiki/M4_carbine