Set up your scope for optimum performance

You are at the range and just shot a pretty decent group with your rimfire rifle at 50 yards Point of impact was slightly off to the right about one quarter inch.

You have to leave the POI set that way because when shooting longer ranges, the POI shifts to the left somewhat. At somewhere around 100 yards, it’s close to dead on. Nothing to worry about. That’s about as close as anyone can hope for. Right?

It was a 5 shot group and three of the shots were touching with two flyers. Oh well, those flyers happen to everyone. They were only on quarter of an inch away from the grouped shots. That happens all the time. Right?

Not really. There could be a number of reasons why you are getting flyers and shifts in point of impact, but one of the first things you should verify is scope set up and adjustment.

Verify scope mounts are solid and tight

As an RSO at my local range, I can’t tell you how much ammo I have seen wasted due to loose or defective scope bases and mounts. I can understand why so many people are hesitant to remove their scopes from the rifle and check the torque on their base and ring screws because it is a real pain.

But shooting an entire box of ammo and still not having your scope zeroed is also a pain, as well as being pretty expensive and frustrating. Just like building a house, the foundation must be right if the rest of it is going to work.

Remove your scope and rings so that you have access to the base mounting screws. Don’t just check tightness or try to tighten them more. A broken screw in your receiver is not a good feeling and requires some special expertise to remove. Avoid that at all costs. Invest in good torque meter to tighten to manufacturers specs.

Remove the base screws before torquing and use a little drop of blue locktite to ensure they don’t back out until you are ready for them to do so.
Torque all of the base screws down and install the bottom half of the rings.
Properly level the scope to the rifle

At this point, making sure the vertical cross hairs of the scope are exactly level to the horizon can eliminate that drift in POI at longer ranges. With a properly set up scope, and in a perfect situation (no wind, or other environmental factors affecting the shot) you should be able to only adjust elevation for longer ranges.

To accomplish this, the rifle with bases and the bottom half of the rings need to be put in a stable condition so that the rifle doesn’t move while you work. A rifle vice or is recommended to get this right. The vice should have the ability to hold down the rifle to prevent movement with either a strap or clamping system.

Here is the vice I use. It can be adjusted to almost any position you can think of to make work easier and it will accommodate any rifle.

With the rifle locked down so it can’t move, use a level on the scope base to level the rifle. Unless there is a flat part of the design on the receiver, this is the only way to ensure it’s level. Once it’s level, make sure it can’t move.

Now, hang a builder’s plumb bob in front of the scope. Perferably with a brightly colored string. The further you can hang it away from the scope the better, as long as you can still see it well.

Turn the scope is the bottom half of the rings until the vertical cross hair is perfectly aligned with the plumb bob string. Then install and torque properly the top half of the rings while intermittently checking to make sure that neither the rifle of the scope has moved.

Once this is complete, your scope is level with the horizon and you shouldn’t see right or left shifts in POI at longer ranges once zero is obtained.

Adjust the ocular lense to your eye

The ocular lense is on the end of the scope you look through. Most scopes have a locking ring or some way to set it once it is adjusted properly.
Looking at a white or light colored wall turn the ocular lense until everything on the wall or in the distance is sharp and clear. Then lock it down. This should never have to be changed unless your eyesight changes substantially.

Adjust parallax

Up until now we have completed set up steps that only need to be completed once. From this point forward, all steps will have to be done before each in order to optimize performance.

Some lower power and less expensive scopes come from the factory with a fixed parallax setting. Usually at 50 -75 yards. While this makes accurate shooting easier it also makes the scope, and therefore your shot more inaccurate at longer ranges.

If you are shooting out to 400 yards, a fixed parallax setting at 50 can cause you to miss at least a few inches depending on the size of the target and other things.

Parallax is the error you see when looking through the scope because the focal plane of the target and the focal plane of the reticle are not aligned. It will appear as if the reticle is moving on the target as you move your head around while looking through the scope.

This could actually cause you to hold in a different place versus where the POI actually is, or in different words, a miss.

This is why scopes designed for long range shooting include a parallax adjustment, usually on the left hand side of the scope opposite the windage adjustment knob (see illustration above). Some scopes will have the adjustment on the objective lense.

If you know the distance you can set that distance on your parallax setting and be very close to correct. A better procedure though is to make the adjustment while you are setting up for the shot.

Slowly turn the parallax knob until the sight picture you get is crystal clear and the cross hairs do no move as you move your head from side to side. This is the perfect setting for the distance you are using. It only takes a few seconds to do this correctly once you get accustomed to it.

Related articles

3 shot zero

When zeroing your rifle, the object should be to match your cross hair intersection with actual point of impact at a specified distance with as few shots as possible.

If your rifle is a bolt action, or an ar style where the bolt can be removed allowing you to see down the barrel, you can align the bore as best you can with the target and believe it or not, this will get you pretty close. Do this at 25 yards.

If it isn’t practical to do this with your rifle there are several bore sighting tools available here on Amazon. You can quickly pay for one of these tools with the ammo you save.

Even though you have bore sighted your rifle, do yourself a favor and start close when you have removed your scope from the rifle then re-installed it. I always start at 25 yards. Fire your first shot and observe where the POI is on the target.

If you are using a lead sled or some type of rest that will hold your rifle steady, you can then put the crosshairs on the bullet hole created by your first shot, and while holding it there, dial elevation and windage controls until the cross hairs are centered on the bullseye.

The only way this works is to have the rifle perfectly stable while making these adjustments. A sled or good bags will help you accomplish this. Depending on how well you do at keeping the rifle steady, your next shot should be in the bull.

If not, repeat the process. You should be able to get zeroed at 25 yards with no more than 3 shots.

Adjust elevation

The last adjustment to make before taking a shot is elevation correction if you are shooting long range beyond your rifle’s dead on hold distance or striving for precision. I always adjust for elevation (longer ranges) and hold for windage.

I do this because wind is usually the cause of being off target horizontally, especially on rimfires. After taking the time to make the adjustment, the wind, more often than not, has changed anyway. Learning to read the wind is another topic within itself. I have written an article here that will provide more detail.

Conclusion

A rifle scope is one of those tools that increases the effectiveness of you as the shooter exponentially. Hopefully this article will help you take full advantage it.