Precision Reflex (PRI)
This is as close as it comes to the Mk12 Mod0 front sight base, manufacturered by the same company that built the Mk12 Mod0 SPR rifle. These are factory new. This model has the cross-bolt set screws that do not penetrate the barrel. Some of the early SPR front sight bases had cross bolts dating back to 2001 era had a solid bottom with set screws that would require flats to be carved into the barrel. This design allowed the shooter to adjust the set screws, or pins to ever so slighly adjust for windage, if his rear sight windage was not operating. This model does not require flats on the barrel. Also, worthy of historical note, the PRI front sight post evolved in its top ring, and has gone through evolutions of completely solid ring to a partial half-moon ring, to its current historicial intepretation by PRI with top circle to add light on the aiming pin and a small cutout in the front.
The cross-bolt screws are more than adequate to hold the sight base in place, and Charlie's recommends adding a little thread locker or red loctite. While the red Loctite will provide for a more secure setting, it will also make for a more permanent mounting.
The folding front sight base is the PRI Original Flip Up Front Sight w/.750" Crossbolt Design fits barrels .750 dia. M4/AR15. Eliminates the shadow cast on optical sights mounted on the M16 Flattop receiver. Lightweight hard coated black anodized aluminum top post provides Low reflection.
The base is solid 4140 cast steel with provision for the gas tube an integral part of the unit. Front post is constructed of T6 6061 hard coated black anodized aluminum. Front post uses a thumb wheel to adjustment front sight elevation. Sight weights 4.9 ounces. The center line of barrel to line of sight is 2.57" the cross bolts are #10-32 x 3/4" socket head cap screws.