shooter521
Certified Glock Nut
My suggestion......
Or the modern equivalent:
And yes, that's the actual setup used by the Arcadia, CA PD. The angle of the photo is misleading; the mount positions the gun so the muzzle points below and inboard of the rider, toward the engine block. Carbine is kept Condition 3 (loaded mag, empty chamber, on-safe) and the mount prevents operation of the charging handle.