A bit rough at first, but a great design - Geissele Maritime Bolt Catch

This bolt release solves for left-handers one of the ergonomic issues that Eugene Stoner designed into his little black rifle. The rear-extended engage and release surfaces on this part allow us southpaws to operate the bolt control with the index finger without breaking grip. It's one of the few advantages left-handers have with the AR platform. Right handers have to fit a long, clumsy lever that extends into the trigger ring to get the same advantage.

Bolt disengagement was a big rough right after installation, but smoothed up with use.

It's hard to understand why Stoner put the controls where he did, but at least the problems can be solved with aftermarket parts. Better to just build your rifle from parts and choose this Geissele release to start.