QD

QD stands for quick detach, a catch-all for hardware that attaches and releases quickly and repeatably without tools. The most common is the QD sling swivel, a spring-loaded push-button stud that snaps into a cup so a sling can come on and off in a second.

The idea extends across the rifle: QD suppressor mounts let a suppressor lock onto a muzzle device and come back to the same place, and QD scope mounts let an optic be pulled and reinstalled near zero. The value is return to zero, a repeatable position after a detach, which is what separates a true QD system from a mount that simply comes off.