Ease of installation and tight tolerances are two descriptors not often used together, especially when referring to firearm parts. However, there is one company that has stood out for years: Geissele Automatics.
Almost 13 years ago, Bill Geissele developed his first product, which was a match AR-15 trigger used by high-power rifle shooters for competing in Civilian Marksmanship Program (CMP) and NRA matches. It didn't take long for soldiers in the U.S. Army's Marksmanship Unit (AMU) and then-U.S. Special Operations Command (USSOCOM) to take notice of those triggers on the firing lines. It even made its way into the legendary Mk12 rifles.
Geissele's popularity within those communities became contagious. Thanks to Geissele's attention to detail and do-it-the-right-way attitude, requests for other products were made by those same military units.
Geissele's next product came in the form of a modular forend for the HK416 and then for the M4 carbine. Tight tolerances and precision fitment make this forend a winner for the elite warfighter who is required to rail-mount aiming devices to his rifle's forend that must be straight and true.
Geissele's Super Precision Rails have become highly desired thanks to the contact surface area the unique 2.25-inch cylindrical barrel nut provides when interfacing with the host rifle's upper receiver, and the rigidity and straightness that results. The rail becomes a solid platform to mount aiming lasers and other devices that will not bend or flex under load. These rails are precision-machined devices that are as rigid as if it were a monolithic upper receiver.
Another example of precision machining coming from Geissele's with its optic mounts. I use the U.S. military's SOPMOD mount for a Vortex Razor HD 1-6X. When I installed the optic into Geissele's mount, it stuck like glue - without the serialized top rings in place. The machining is a work of perfection. On a rail, Geissele's mounts even click onto Picatinny rails. Once dropped onto such rail sections, there is no front-to-back or left-to-right play due to the mount's four closely toleranced recoil-stop shear lugs. These lugs offer shooters a snug, repeatable connection between the rail and Geissele's mount.
Geissele recommends torquing the cross bolts to 72 inch-pounds (in.-lbs.). However, it also states that using a torque wrench is unnecessary for the optic to return to zero it is removed and reinstalled to the same location; Turn each clamping nut a quarter turn beyond hand-tight, which should be sufficient for recovering optical zero.