You might be a gunsmith, you might be an engineer, and you may have been mounting scopes on rifles since a date that borders on ending with B.C. You might be doing it wrong. “It’s not your fault,” (Good Will Hunting, 1997). There’s more to mounting a riflescope than commonly thought. Overall, it is a simple process, but must be done correctly for proper optic function and reliability. Save yourself time, frustration, and ammunition by doing things right on the front end.
Often overlooked, many people highly underestimate the importance of quality rings and bases. They become an afterthought in the rifle/riflescope purchase process and get skimped on. Remember, these are the components that connect the riflescope to the rifle. If they are not up to the job, you’re stumbling out of the gate.
When setting eye relief, it’s important to do so on the riflescope’s maximum magnification. With the rings still loose, slide the scope fore and aft and look through it to find its optimal position/eye relief. Shoulder the rifle several times and bring the scope to you during the process. Make adjustments as needed. This will ensure the best sight picture throughout the zoom range.
After eyeballing the reticle as close to plum as possible, it’s time to break out the bubble levels. With the rifle braced and locked in place, set one bubble level on a flat surface of the rifle (generally on the receiver), the other on the riflescope (generally on top of the elevation turret). Gently turn the scope in the rings until both read level. Note: Just because your reticle may appear to be slightly canted after proper mounting, doesn’t mean it is. Right-handed shooters often notice a perceived subtle cant to the left and left-handed shooters the opposite. It’s not the reticle that’s canted, but the rifle itself when brought to the shoulder.
A common misconception is the need to really crank ring screws to ensure the scope doesn’t slip under recoil. Over torqueing can lead to tracking issues due to flexing of the outer scope tube, which impedes functioning of the internal erector tube (the part that moves when adjusting your turrets). Crimped scope tubes can also result, which is an unfortunate and permanent issue. Ring halves are not supposed to touch. Once tightened in an alternating fashion, much like you would tighten the lug nuts on a tire, there should be equal spacing/gap between the top half and bottom half of the rings (applies to horizontally split rings). As a general rule, 15 to 18 inch pounds on the rings is more than sufficient, even for magnum calibers. You can be slightly more aggressive with the ring to base connection with 25 to 35 inch pounds of torque.
Recommended by many, it is not necessary to use Thread Locker on your ring or base screws. Thread Locker lubricates screw threads, causing a wet-torque which can actually lead to over-torqueing. Your torque wrench might read 15 inch pounds, but in reality be much higher.
Implement these tips into your riflescope mounting process to get the most out of your rifle and the optic that sits atop it.
— by Mark Boardman