If you’re more than a casual shooter you probably know not to crank down your scope mounts and scope rings as tight as humanly possible.
You might wonder why though. After all, they’re such basic components, just small pieces of aluminum or steel for the bases, and some round clamps to hold your scope in place.
Simple right?
Well, yes and no.
The parts aren’t complicated but properly setting them up is critical, particularly when you consider you’re likely clamping an expensive scope into place. The bottom line is properly torquing your rings and bases into place not only protects your investment but also ensures you get the maximum performance you paid for.
It's More Than Just Not Stripping the Screws
Of course, the most obvious reason to properly torque the screws is so you don’t snap off their heads, or even worse, strip the threads in an aluminum receiver or scope mount. There pretty much isn’t anything worse to deal with when trying to set up a rifle.
Using a torque limiter to apply the proper amount of force will prevent this. So, let’s just agree there’s no good reason that ever has to happen again and move on. That said, not over-torqueing the scope rings is way more important than simply not screwing up your screws.
The Scope Tube is Designed to be Round
The goal of properly torquing your scope rings is to keep round things round.
When it comes to rifle scopes, there’s a lot of magic inside the tube you can’t see. That magic consists of precision parts made to extremely tight tolerances, sometimes as tight as a few 10,000ths of an inch. When you over-torque your ring tops, you distort the tube. It may not be visible to you, but it happens.
This actually hurts the performance of your rifle scope, most notably loss of windage and elevation adjustment for starters. If you’re overzealous you can damage the tube enough that you see a crimp when you take it out of the rings. If this happens, congratulations, you just damaged all that precision engineering and performance you paid so much money for.
Look at it this way, if scopes performed better with a cross section that looks like Stewie Griffin’s head, they’d design it that way. The cutaway of a scope, courtesy of Leupold, shown here illustrates some of the parts in a scope. The scope parts are a system and distorting or crushing the tube is going to negatively affect that system.
It's Physics
Another danger of over-tightening your scope rings is you can actually lengthen the tube. Seems crazy right? It’s not.
If you reduce the diameter of the tube at the scope ring, the material doesn’t just go away, it goes forward and backward from the ring.
The scope’s lenses are attached to the inside of the tube, as is the zoom/erector system, the lenses of which are also attached to the inside of the tube. Lengthening the tube will increase the distance between the lenses, and even a thousandth of an inch can affect the optical performance.
Yes, the scope will still work, but once again it affects the design and performance for which you spend good money. Don’t mess it up by over tightening your scope rings. Use some sort of torque limiter and save yourself making unwanted alterations to your scope tube.
True or False:
Let’s look at some long-held fallacies about scope mounting.
Statement: More torque is better.
Reality: False. More toque is not better. If anything, it’d be better to be under-torqued slightly than over-torqued. For instance, for a 25 in/lb torque spec, you’d be better off hitting about 20 in/lb rather than say 35 in/lb.
Statement: You can’t go wrong if you use the little “L” shaped wrench in the package.
Reality: No. If using the long end as the handle end for tightening, you can definitely over-torque your screws.
Statement: Both sides of the scope rings should be touching.
Reality: That’s nonsense. If both sides are touching, you’ve likely distorted or crushed your scope tube. Scope rings are designed to have a slight gap between ring cap and ring body. What you want to do is make the ring gap as even as possible on both sides of the scope ring.
Statement: Always use a thread locker, like Loctite.
Reality: Surprisingly, the answer is no. Many scope mount and scope rings fasteners have a thread locking “patch” on them from the factory. If they don’t, that’s ok. If properly torqued, the scope ring screws will rarely come loose. Thread lockers can lubricate the threads and actually make you over torque the screws.
What It Means for You
Properly torquing your scope base and rings is not only going to save you potential problems and money, but it’s going to give you optimum performance, adjustability, and consistency. This will also help accuracy. The cost of getting some sort of torque limiter or torque wrench pales in comparison to the price of premium optics. It’s worth the money to do the job right.