How to zero a scope

I was working hard, trying to successfully attempt the almost impossible technique of moving quietly enough in the crisp autumn woods to hopefully catch a glimpse of the whitetailed deer I was dogging, yet keeping it on the move, travelling in the direction of a buddy I’d placed on a ridgeline in hopes of pushing a deer out to him. The pressed-down leaves in the deer’s hoofprints were still rising from being pushed into the ground, and occasionally I could hear a crash ahead of me. I knew I was moving the deer successfully, and right towards my buddy…


BANG! BANG!! Two shots from directly in front of me, about 100 yards off, made my heart jump for two reasons: It scared the shit out of me, and also I knew all my hard work slogging through the Maine woods had paid off. I trotted up to my buddy, to see him practically hyperventilating. “Huge deer…*gasp* biggest I’ve ever seen…about 50 yards away! I put two into him, he ran over that ridge.” I had him sit, we relaxed and had some trail mix, and let the woods settle down, so that the big buck would hunker down and expire gently without us pushing him around. A half hour later, I got up and he directed me to where the deer had been. Sure enough, deep, big fresh prints in the mud. No blood or hair though. I tracked the prints over the ridge, for about 300 yards. Still no blood or hair. I marked the spot where I left the trail and went back to my buddy.


I asked, “So, what distance is your rifle zeroed in for? At fifty yards that should have been a solid hit if it’s sighted in properly.”


I looked at me quizzically. “Sighted in? Huh? I just bought the gun, that was the first time I’d shot it!”


Sure enough, when we went to sight the gun in, it was shooting a foot and a half low; he’d shot into the ground at the deer’s feet. Oops. Imagine if he’d been desperate, and that deer was the only chance he’d had to feed his family in a week and a half….he’d be a hurtin’ unit instead of just an embarrassed one.


At the shop, this is hands down one of the biggest problems people have, even though once you get the basics of zeroing down, it’s very simple. People would get so frustrated they would bring their guns to me to sight in, even though I’d explain to them up, down, left, and right that everyone has different body types, cheek welds to stock, trigger pull and shooting technique. You can’t sight a rifle in for someone else and guarantee it’ll be, as one customer always said, “sight it dead nuts!!!” So, sight it in for you, and you’ll be good to go!


So how do we do this? First, we need to understand what we’re doing. All that is happening when we sight in a scope is changing a visual reference point (the crosshairs, red dot, etc) in relation to a fixed point (your eye) in order to change the orientation of the gun with a third point (the target). Think of three dots in a line, with the first one representing your eye, the middle one the aiming system, and the third the target. If you move that middle dot, even a fraction of an inch, you need to move the first dot in order to keep all three dots in line. Simple geometry. And that’s all that’s going on with a scope or sighting system: using one adjustable point to keep two outside points in line.


So, to accomplish this, we need to go in steps. Step one: make sure ALL the screw in your scope mounting system (rings, bases, etc.) are tight! If they are not, the scope will move around on you and make zeroing an inconsistent nightmare. Step two: boresight (if you can).


Boresighting is simply getting the scope roughly in line with the bore. There are boresighters through many different companies that will help accomplish this task, (and a local gun shop and almost certainly help you out here) however, keeping things simple, you can do it manually if you have a gun (such as a bolt-action rifle) that you can see through the bore when you remove the bolt. Place the gun on a solid surface, preferably at the range, and fix the gun so it won’t move. Look down the bore at a target (the further away the better), and once it is centered, look through the scope and, using the scope adjustments, bring the crosshairs to the target. Your rifle is now bore-sighted. Start shooting up close (25 yards), get your bullet close to desired point of impact, then go out further to 100 yards. Just remember, though: BORESIGHTED IS NOT SIGHTED IN!!! It’s just getting you on the paper at a close distance.




The adjustments are under caps on the scope. Unscrew the caps, and you will see something like this:



Usually there will be a slot for a screwdriver or coin (but not always) and little lines. The lines represent a distance the point of impact will change, usually at a known distance (100 yards is standard). Check the manual for the scope to find out how much the point will change (though sometimes it’s printed on the dial.). For scopes, 1/4″ per “click” (detent stops on the scope adjustment) at 100 yards is the norm, and 1/2″ at 100 yards is standard for most red-dot sights. So if you have a regular rifle scope, and your bullet point of impact is six inches high and three inches left at 100 yards, you will move the vertical adjustment (at the top of the scope) 24 clicks (6″ off, multiplied by 4, since there are 4 “clicks” per inch), and the horizontal adjustment (on the side of the scope) 12 “clicks” (3″ x 4 clicks). This should get you close to where you want to be, though fine-tuning a few clicks in any direction may be necessary.


Just a word of warning, and this gets some people confused: If you are sighting in the gun at 50 yards (one-half the distance of what most scope clicks are graded for) you will need to DOUBLE the amount of clicks needed to move the point of impact. At 25 yards, one quarter of the distance, you will need to QUADRUPLE the amount of clicks necessary. Most people think “oh, it’s half the distance, so I’ll need half the adjustment.” Not so…it’s actually the opposite. So, in order to move the point of impact three inches at 25 yards with a 1/4″ click adjustment scope, you will actually need to move the adjustment 48 clicks (3″ x 4 clicks/inch x 4) to change the point of impact the desired result. It’s confusing, and really screws many people up, but once you get it, it’s pretty easy to retain, and you can be the wonder of all your gun buddies!


Now that you’re sighted in, you’ll be that much more effective when you REALLY need your rifle! Best of luck!!



20 comments… add one
  • j.r. guerra in s. tx. May 1, 2013, 9:00 am

    Thank you for your article. Sighting in and making sure your scope retains its zero is vitally important. Another important note – when purchasing ammunition, checking the lot # (inside flap of box) to make sure the boxes are of the same # is good advice too. Ammunition is made in batches, and the # tells the buyer it was made at same time as the matching #. I always buy at least 5 boxes of matching # to be more sure of consistency.

    Thanks again.

  • Jason May 1, 2013, 4:28 pm

    Man oh man, I loved the story – you told it well. I actually gasped when your buddy responded with the question about sighting in his scope. What a mistake & I gather it is more common than most realize. Great intro to this article & a great lesson about being prepared.

  • navdan May 1, 2013, 5:38 pm

    Thanks for these posts.

    Other than very basic and minimal firearms training in the Navy, most of what I know about rifles and handguns is self-taught and self-researched. Articles like these help reinforce the things I’ve learned that happen to be correct, and give me more insight into things I just happened to not pick up on over time (for example: conceptually I had an idea of what boresighting was, I had a guess as to how boresighting tools are used, and I presumed that the process was pretty easy…but I just was never really introduced to it and managed to never have it explained, despite its simplicity).

    Now, if there was only an article to let me know if the process I’ve ended up teaching myself to do to clean my guns is acceptable or not…

  • Robert May 1, 2013, 7:09 pm

    The advice to make sure the rings are tight is dangerous. Most human males over-tighten these screws and often damage the scope in the process. Usually the torque required is less than 20 INCH-pounds for steel rings and less than 15 inch-pounds for aluminum rings. That’s not much torque. index finger and thumb on a properly fitting bit will usually do the trick, or get a torque wrench/driver (make sure it is INCH-POUNDS).

  • Ray May 1, 2013, 8:31 pm

    The only thing I own with a scope on it is my M-40A1 . I never shoot it, I’d much rather take my NM M-1 or one of the ’03s out. Few of the younger people will believe this but that ’03 is a sub MOA rifle. Basicly you can hit anything you can see with ether one.

  • T.R. May 1, 2013, 9:52 pm

    Step 1. buy an Obama picture ………………….

    • StukaPilot May 2, 2013, 11:03 pm

      Never mind that stuff. Obama is a symptom, not cause. The whole System is rotten and has to go.

      • Jason May 3, 2013, 1:01 am

        Step 2. Buy a picture of the system ………

        • Navdan May 3, 2013, 10:43 pm


      • T.R. May 4, 2013, 7:37 pm

        I agree the Washington District Soviet needs a night of the long knives purge by the people .

  • Ray May 2, 2013, 6:12 am

    One of the most common mistakes I see is, People sight there rifle for say 100 yards. Then have a cow when the rifle won’t hit point of aim at 200 yards. It’s like they have never heard of bullet drop. My other favorite “F” up is , people who think that the 5.56/.223 is a 400 yard hunting rifle. You MIGHT kill a deer at that range with a .223 , and then you might just wound the poor beast, and spend the rest of the day tracking. Then there are the ones that like to hunt a 170lb. whitetail with a .300 win-mag ,they bought last week and never -EVER shot before. Sorry for the rant guys ,but the gun-stooped have been out in force in Ky. this year.

    • T.R. May 4, 2013, 12:20 pm

      See thats just it , my general rule about long range is pretty simple , and that is : if your target is that far away , I dont need to be shooting at it at all . My family isn’t going to starve or even care if I dont bag anything . Just sayin .

  • Spud May 2, 2013, 8:01 am

    Some detailed instruction on shooting just a couple rounds, then with the rifle secured aiming at the first group just dial the scope to center target. Makes for much less ammo wasted in these ammo deprived days. A gun vice also makes this much easier also a buddy to do the adjustments while you aim helps.

    • StukaPilot May 2, 2013, 11:06 pm

      I have no vices. But I do have a gun vise.

  • StukaPilot May 2, 2013, 11:08 pm

    Thanks for this one. I’m going to the range in a few to zero an M1a. Would have gotten it wrong on the 25 yd. zero…now I’ll get it right.

    • Jason May 3, 2013, 1:28 am

      By the way, your blog is pretty incredible & looks like you put in a TON of work!

  • jeanswest371-jeanswest371--频道--文章 May 3, 2013, 4:37 am

    How to zero a scope

    • Jason May 3, 2013, 8:59 am

      Hey Spammy,

      This is about an attachment to a rifle NOT training a point of view.

    • T.R. May 4, 2013, 12:09 pm

      Gook !!!!!!! open your eyes there Chang !

  • Anonymous May 7, 2013, 10:39 pm

    **Easy Way**

    Set-up @ 25 yds.
    Take 3 shots (an average group)
    Look through the scope putting the crosshairs on bullseye
    Move the crosshairs (using the turrets) to the center of the three shot group. **Is is very important that the rifle does not move when adjusting the turrets**
    The crosshairs are now pointing where the barrel is actually aiming.
    Move out to 100yds and repeat process.


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