Ever had a scope you just couldn’t get properly sighted in? Assuming your rifle and ammo are good, start with the scope, rings and bases to isolate and solve the problem.
Once, on the way into remote desert mountains in southern Arizona, I paused to check the zero of my lightweight custom mountain rifle. I’d flown to Tucson with the rifle, and wanted to be sure I was prepared to make a clean, precise shot on a tiny-bodied coues deer buck.
To my frustration, I found the rifle hit way off. As in, a foot to the right at 100 yards. Worse, it wouldn’t shoot small groups, and I couldn’t get the scope to adjust properly and hold zero. It was a Zeiss; a premium optic that should be consistent and reliable.
Finally, a full box of ammo into the ordeal, I put on my forensics cap and began examining the rifle. I confirmed that the action bolts were torqued properly. I checked that the scope ring screws were as well. Lastly, I went to the scope bases—and found the problem. One of the side-mounted screws that clamps the rear ring in place had come loose. No wonder my point of impact had been way to one side.
Once that screw was tightened, the rifle produced its customary small groups, and the scope held zero perfectly.
The inability to get a rifle sighted in can come from several sources. Your rifle could have a problem. Or it just may not like the loads you’re feeding it. It could—(shocking thought!)—even be you, the shooter, that’s inconsistent. However, scope and scope mounting-system issues are frequently the culprit, and that’s what we’re here to explore in this article.
When you think about it, riflescopes and the rings that hold them in place are rather amazing creations. It’s surprising that anything could hold a glass telescope with many moving parts in place while a controlled explosion and a whole bunch of Newton’s Law occurs inside the rifle that scope is mounted to.
Good bases and rings do hold quality scopes precisely in place. Not just for a while, but as hundreds, even thousands of shots create mini earthquakes.
However, some scopes just won’t hold zero, and some bases and rings just won’t hold tight. Usually, that’s because they’re either cheap (let’s call it what it is), or they’ve been improperly mounted.
Either is extremely frustrating. Both must be resolved before the rifle can perform properly.
What causes scopes, scope rings, or bases to come loose? There are a variety of possibilities, but the most common ones are recoil—when a scope is mounted improperly—and vibration. As in, vibration in the belly of an airplane, or the rifle case mounted to your ATV, or behind the seat of your pickup.
Recoil, of course, is the primary suspect. When a cartridge ignites and the gunpowder inside explodes, thrusting the projectile from zero to Mach 2 or 3 in a nanosecond, there’s a whole lot of seismic activity going on. Up top, that scope full of glass and aluminum parts has to hang on, and what’s more, all those parts have to stay stable. Worst, there are several potential “weak links” between the scope and the rifle.
If your scope rings aren’t positioned properly and torqued properly, the scope can actually slide forward a fraction inside the rings each time the rifle recoils rearward.