How to Troubleshoot Your Riflescope Zeroing Problems
Having issues sighting in your rifle? Here’s the cure
You see it every year at the range. Some poor guy bangs round after round downrange, cussing and twirling his adjustment dials in confusion as shots scatter over a sheet of paper the size of a barn. I’ve seen people burn through 20 rounds, throw up their hands in frustration and go home, no closer to dropping bullets where aimed than when they started. That’s a pity, especially when you can sight-in a scoped rifle with as few as two shots.
1. Bore Sighting Isn’t Boring
Before you fire that first shot, bore-sight the gun. Use a mechanical or laser bore-sighter or just eyeball it. Eyeballing might sound rather coarse, but it’s cheap and it works. The trick is to mount the rifle in a vice or cradle so that it doesn’t move easily. (A cardboard box with notches on two top edges to hold the rifle works well in a pinch. Weight the bottom to prevent sliding.)
Remove the bolt from the action. Peer down the barrel and adjust the rifle to visually center a small bull’s-eye at about 30 yards. Now, without moving the rifle, turn the turrets until the reticle centers over the bull’s-eye. Barrel and scope should now be pointing to the same place.
Now you face a small dilemma. Sometimes bore-sighting is good enough to put you on paper at 100 yards, sometimes it’s not. Do you risk a shot or start closer? I find it generally pays to take that first poke from about 30 yards where you’re sure to hit paper. After the first hole appears on the target, realign your rifle with the crosshair exactly where it was for your first shot (over the bull.) Again watch the reticle while turning the windage and elevation dials to move the crosshair over bullet hole. Bingo. The reticle is now pointed exactly where the barrel is throwing its shots. You’re zeroed for 30 yards but also for about 200 to 250 yards. But you’ll be high at 100 yards.
Why high? Because your barrel is angled upward slightly in relation to the scope. You’re throwing your bullet up. It crosses the line-of-sight at about 30 yards, strikes high at 100 yards, even higher at 150 to 180 yards, and then begins to drop closer to the line-of-sight until crossing it at about 250 to 300 yards. The exact trajectory curve depends on your bullet mass, shape (B.C.) and muzzle velocity.
2. Rise of the Bullet
It may seem obvious to veteran shooters, but it’s worth mentioning that bullets do not rise above the axis of the bore. The instant they exit, gravity begins pulling them down. It’s only because we cant barrels upward slightly that bullet seem to rise, striking high at 100 and 200 yards.
After you’re dead-on at 30 yards, shift to 100 yards to perfect things. Naturally, you’re going to use a steady rest to remove all human error. Bean bags, tripods, bipods, perhaps some sort of cradle. This isn’t a contest to see how well you shoot, but a series of mechanical adjustments to make your scope/rifle shoot where you want. So minimize all human errors.
From your rock-steady position, fire at the bull’s-eye. Don’t flinch, jerk the trigger, or close your eyes. If you don’t know you’re doing this, set up a camera to film yourself. Record in slow-motion for a real tell. If you see flinching, do a bunch of dry firing until you’re smooth, dead-steady perfect.
Your first 100-yard shot should land high, perhaps slightly to either side. It’s tempting at this point to dial in correction. Big mistake. A single shot could have been a flier. Or you could have pulled it. Or your rifle might group as poorly as 2 MOA, in which case any shot could be an inch off-center. This is why the standard rule is to take three shots and average the group center, then make your corrections. But before you do any dialing…
3. What’s Your Click Adjustment?
Determine whether your scope moves 1/2-, 1/4-, or 1/8-inch per click at 100 yards. Most are 1/4-inch click. In that case, you’ll dial in four clicks to shift point-of-impact 1-inch at 100 yards. So, if your first shot hit 4 inches high, turn the elevation turret 16 clicks down. If it also hit 2 inches left, dial 8 clicks right. And so on. Four clicks for every inch of movement needed at 100 yards. And get ready for a potential surprise, which we’ll discuss next.
Now take your second shot. Did it move left 1-inch and up 2 inches? If not, don’t panic and don’t move those dials! Sometimes erector tubes (which move internally to adjust reticle position as you see it) don’t shift when you screw the dials, but do shift after recoil jars them. So shoot two more times for a much more accurate picture of where your point-of-aim shifted. If one shot is in the original group and the other two have moved where they were supposed to, your scope’s erector tube was probably stuck after your initial adjustment.
Be cognitive of this. If you adjust the turret after the first shot to correct, you might end up with a double movement on the next shot because the initial recoil shook the erector tube loose, but then you gave it another adjustment, leading to a double adjustment on that second shot. If you don’t understand what’s going on, you could be pulling your hair and chasing holes on paper all day.
4. Defective Scope Work-Around
This seems like a defective scope — and probably is. But you’d be amazed how many scopes do this. Even quite expensive ones. If you’re planning to dial for distance shooting, such a sticky scope won’t suffice. If you just want to fix your zero and not dial, you can live with inconsistent adjustments.
There are a couple of ways to minimize erector tube/turret sticking while zeroing. One is to “rap the cap.” After you turn in your adjustment clicks, tap the turret top with a plastic or wood screwdriver handle several times. You’re trying to mimic recoil to jar loose the sticky screw/tube junction. The other trick is to memorize the turret setting (number) and dial a complete rotation past it, then come back, then dial the correction. The added pressure of the huge adjustment should clear the sticky point. Combine rapping at the end of the rotational adjustment to double your chances for success. This seems like an odious work-around for an expensive scope, but not all of us can afford expensive scopes. Tricks like this can make our otherwise effective scopes suffice. I’ve seen some “sticky” inexpensive scopes perform for 30 years without ever losing zero. Now let’s investigate other scope zeroing problems.
5. Incorrect Click Movement
What if your scope adjustments move only half the distance they were supposed to – or double? Either you miscounted clicks, misread the click adjustment rate, or own a scope that isn’t as accurate as its manufacturer claims. The latter happens almost as often as the former, but it isn’t the end of the world. A scope that doesn’t adjust exactly 1/4-inch each click can still be a perfectly trustworthy, functioning hunting scope once it’s sighted in. Just don’t try cranking-in new range adjustments while afield and expect them to be accurate.
One other error that is sometimes made while sighting-in scopes baffles those engaged in making it. They dial corrections left and right and up and down and the bullets land nowhere close to where they should. The entire scope seems schizophrenic. Check to see if it’s mounted “upside down.” Hey, it happens. Someone (no finger pointing here) set the thing in its rings with the elevation turret turned to the left side of the rifle and the windage turret on top. So when you adjust the dial that indicates R for right, you really move the reticle up or down. When you turn the Up dial, you shift the reticle left or right. Yeah, pretty hard to correlate those moves. Some shooters intentionally mount scopes this way to better clear the ejection port, knowing that the windage and elevation dials are then reversed.
6. Cold Barrel Versus Hot
Another concern is barrel heat. Many rifles shoot to slightly different points when hot than when cold. Don’t zero a hot barrel and then wonder why it shoots low or high for that first shot from a cold barrel.
For hunters it makes the most sense to zero for the cold barrel because that’s what you’ll be using when that buck shows up after long hours of boredom. While sighting-in, wait at least a minute between shots. When you think you’re near perfection, let the barrel fully cool before firing your final zero shot. If it’s not quite right, completely cool and try again. You’re looking for consistent point-of-impact from a cold barrel every time. If warm barrel hits shift an inch or so from cold, it’s not too big of a deal until you’re 300 yards and farther. Often second and third shots at game are running, so you’re not going to get gnat’s hair precision anyway. Ideally you’d tweak stock bedding and try to alleviate the cold/hot differences, but I wouldn’t divorce a rifle that shot lights out from a cold barrel. It usually takes two or three more shots to heat a sporter barrel anyway. By that point you’ll either be breaking out your skinning knife or vowing to become a better shot.
7. Thin Barrels and Magnum Overheating
Thin barrels and high-volume cartridges can be a frustrating combination. The thinner the barrel, the faster it heats. The larger the powder volume, the hotter it shoots. Together the two can really mess you up. The combination can be accurate and deadly for first shot, cold barrel consistency, but after two or three rounds ignite, the barrel heats so much that it “wanders,” meaning its molecular structure swells and changes stresses enough to alter shots. You can burn up your annual ammo budget chasing holes with this setup, so take your time and allow magnum barrels to cool fully between shots when zeroing and testing for group size.
8. Dirty Barrel Versus Clean
The dirty barrel syndrome is a classic. Many, if not most, rifles shoot to slightly different impact points when squeaky clean rather than when fouled with one to three shots. This has nothing to do with heat, just carbon and copper fouling. Almost everyone fires a couple of shots after each barrel cleaning to maintain consistency. This makes way more sense than trying to work with a scrubbed barrel on every hunt. After you zero in camp or miss a shot or two, you’re henceforth working with a dirty barrel anyway. Do your final rifle zeroing and group testing with a fouled barrel, cleaning it when accuracy begins to suffer. With many rifles this doesn’t happen for dozens, sometimes even hundreds of rounds.
Read More on Riflescopes Here.
9. Hard Surface or Soft?
Finally, you must decide whether to zero off a hard rest, padded rest, or no rest. The smart hunter’s money is on some kind of support to steady your shot, but not all rests are created equal. A short, steel bipod clipped to the fore-end swivel stud makes a rock steady support, but a direct, hard contact that can throw shots higher or lower than shooting from a padded rest. The fore or back pressure you put into the rifle/bipod also changes impact point.
A slightly softer rest such as a rubber coated yoke atop a sitting-height tripod or bipod might not alter hits as much. And shooting with your lead hand resting atop any hard surface introduces another potential response. So what’s it going to be? You choice should hinge on where/how you get most of your hunting shots. Hunting hilly woodlands suggests a prone fixed bipod is going to be rarely used. Alpine mountain hunting suggests prone could work much of the time — and would certainly be useful for those long shots. Trackers and still-hunters in the big woods, swamps and cattail sloughs will most often shoot offhand using no rest or, at best, leaning against a tree. Only you can determine what’s best for you, but whatever it is, zero from that rest. I find a rubber coated yoke atop a hand-held bipod or tripod the most versatile option. It can be adjusted to accommodate a wide variety of shooting positions and uphill/downhill angles. If you must switch to a standing height support, the recoil jump should be similar. And even a handheld recoil response is not the much different.