Scope Mounting For Distance | Taking a 22LR 450 yards

This is not a how-to on ring height or general scope mounting. Enough has been written about that. This is going to be an in-depth guide on how to find the optic and base system requirements that you need for how far you want to shoot with your rifle. 

For this exercise I’m going to be using my personal 22LR rifle, a CZ 457 Varmint Precision Trainer, as I recently used it in a way that demonstrates the methodology - And I also posted about it on Reddit's /LongRange sub. For this I brought the rifle out to 450 yards with a 25-yard zero. How do you get a 22 Long Rifle out to 450 yards? It’s not as difficult as you may think. 

Before getting into this I’d like to make clear how modern riflescopes work. Inside the scope is something called the erector tube, and contained in its assembly are a few magnification lenses. One of the most important jobs the erector assembly has is that it provides the movement of the optical system left and right and up and down. It does this using using the turrets and a spring system to push the forward part of the erector assembly left, right, up and down. At the rear towards the magnification ring the erector assembly has a spherical bearing that allows for this movement. 

The erector assembly’s movement is often limited by the internal clearance within the scope’s main tube. That clearance along with the turret’s threaded erector screw length create the scope’s specifications on total elevation and windage. In the middle of the extremes is the scope’s center point where the optical system is aligned parallel to the scope tube’s body. So, if a scope has 30 MRAD worth of total elevation travel, in the neutral centered position it’ll have 15 MRAD up and 15 MRAD down. Also, it’s important to note that due to optical ‘flipping’, the erector assembly’s relative motion is actually opposite of what it’s doing for us on the optical center line that we use for targeting. If you want to see this concept in action another way, use your phone’s camera to try and take a picture through a scope or binocular and you’ll see how movements are backwards as you adjust the camera’s position around. 

The thing about your rifle’s zero that is very important here is how much cant your scope’s mounting setup has while it’s zeroed. What’s cant? Think of it like the difference between the scope’s mechanical centerline and the rifle bore’s centerline and if they’re parallel or not. This is where scope rings and/or bases with cant built into them come into play. The typical way bases are sold is with a number and ‘MOA’. Probably the most common way bases are sold is with zero MOA and not labeled at all – this gives you a [roughly] parallel setup between the scope and barrel. What this means is that when you zero your rifle at say, 100 yards, it’s most likely going to end up very close to the erector tube in the scope being parallel with the bore. So if you have a 30 MRAD scope like the Match Pro ED, you’re going to be zeroed out with roughly 15 MRAD of travel to the down side and to the up side. 

If you’ll notice, only half of the travel specification is really usable for elevation to shoot further when using a zero cant ring/base setup. How do we change that? We change the setup using a canted base. These setups mount the scope rings and scope with the objective end down and the eye piece higher so that the rifle bore and scope centerlines are not parallel, they’re converging. This gives the bore centerline a headstart in relation to the scope’s centerline. How much? Well, it depends on the base. Manufacturers typically make 10, 20, 30, 40 and even larger MOA bases. 

In the image above you’ll see three lines. They’re depicting the bore’s centerline, the scope’s mechanical centerline, and the scope’s optical line. It shows the convergence and relationship of all three lines.

So far we’re working in MRAD here. What’s MOA? They’re both units of angular measurement. One’s a finer tooth comb than the other. The MRAD measurement is base 10 and often the larger tooth comb. The MOA measurement is typically finer and usually described in whole, 1/2’s, 1/4’s or 1/8’s in the optics world while MRAD is usally graduated in tenths e.g. 1.1. 

To figure out our math on what base we should be using, we take the known amount we want to make up, then convert it. There are simple calculators online to do this (it’s 1mrad × (60 × 180)/1000π = 3.438 MOA). We know we were short by 2.5 MRAD, this equals 8.59 MOA. So, if we get a 10 MOA base we should be able to just squeak out enough to get to 450 yards.

In other words, your typical canted bases come out like this:

•         10 MOA equals 2.9 MRAD
•         20 MOA equals 5.8 MRAD
•         30 MOA equals 8.7 MRAD
•         40 MOA equals 11.6 MRAD

In my case, I wanted more than that and to be able to go further, and with a 25-yard zero. I like the Area419 30 MOA base for the 457 so I went with that. 30 MOA = 8.72 MRAD. This ended up giving my rifle setup the ability to dial exactly 23 MRAD out of the Match Pro ED with a 25-yard zero. The math on this works out almost spot-on. 

A parallel zero MOA base would give me roughly 15 MRAD of dial. Take the 8.7 MRAD of the 30 MOA base and add it to that 15 since it would create a converging point of the scope and bore line, and you get 23.7 MRAD – pretty close to where I actually ended up.

How much would a 40 MOA base give a 30 MRAD scope to dial? 40 MOA equals 11.6 MRAD, add that to the 15 MRAD and it would give me roughly 26.6 MRAD. Looking at the ballistic app, that will take the little 22LR out of my rifle out to about 480 yards without having to use the reticle to holdover at all.

Your rifle’s zero range has some effect on this scenario, but maybe not as much as you’d think. If I changed my zero from 25 yards all the way out to 100 yards, it changes the amount to dial about 1.8 MRAD – but it does me no good as the scope’s erector tube will still be at the same top end limit in relation to the bore line. That’s not the end of the analysis though. The most important part about zero range is that you’re getting it at a short enough or long enough distance to be useful for your purpose. Maybe you need to be able to make short shots – So you’ll want a zero to facilitate that. If you go with too much cant on your scope setup, you may find that you can’t obtain a zero at a shorter distance you need. The main takeaway with zero is that the distance you zero out at isn't changing the relationship between the scope's mechanical centerline and the bore line - it won't give you a maximum distance advantage.

The first step is to decide what your distance goal is with your rifle and ammunition load. Run that ammunition and bullet data through your favorite ballistic solver app online or on your phone or Kestrel. In my case, I used Bushnell Ballistics, a free app for your phone. Bushnell Ballistics has 22LR ballistic coefficients already in it, so I just used those preloaded bullets and had them at 1080 FPS. This told me that I needed 23.5 MRAD to get from my 25-yard zero to 450 yards.

When it comes to the rifle scope, you’re going to need to pick something that has a combination of enough total travel and potentially enough holdover to get you to your destination. For this I was using the Match Pro ED with 30 MRAD of elevation travel, and it has 40 MRAD of holdover on the DM2 reticle – but that’s at 5x. So, in a perfect world scenario you’re talking 70 MRAD of total elevation ability. However, on a first focal plane scope you’ll often lose some holdover ability as you crank the magnification up as the reticle magnifies out of view. The reticle at 30x only has about 6 MRAD of visible holdover. That means we’ve dropped down to only 36 MRAD, and we only need 23.5 to get to 450 yards. So, we’re good – except, well – maybe not. Let’s look further. 

This concept really works on any scope whether you already have one or are looking to get one for going long range. You can apply this pretty simple formula to get a ballpark figure of what a particular setup will do for you without ever even having the scope mounted yet. It can also aid in telling you if the scope you’re interested in has enough travel to get the job done.

The basic formula is take the total elevation travel on the scope you have or are considering, then divide it in half. That’s about the amount you’ll have to work with on a zero MOA base. If you want more, decide how much based on the distance you want to shoot, and pick the canted base amount that gets you there.

For example, the original 6-24x50 Match Pro with its 18 MRAD of travel may not be optimal for trying to basically do 22LR ELR (extreme long range) shooting to 450 yards – but we could get there. Here’s how.

We take that 18MRAD and divide by 2 (to get centerline) for 9 MRAD, and with a 40 MOA (11.6 MRAD) base we’d have around 20.6 MRAD of elevation to dial. We’d have to hold over with the reticle that extra 3 MRAD to hit the target at 450 yards that needed 23.5 MRAD to get there. If you were paying attention in this scenario you may have noticed a problem though – 11.6 MRAD on the base would bury our elevation travel out on the bottom end and we couldn’t obtain a proper zero. Our base setup will be limited to 9 MRAD or we won’t be able to get a zero as the erector tube and/or dial will be maxed out. This means we’d be limited to a 30 MOA base, which is 8.7 MRAD. We add up 9 MRAD plus 8.7 MRAD and we get 17.7 MRAD, which is 5.8 MRAD short and we’d have to get to 450 yards with holding over with the reticle 5.8 MRAD. Not ideal, but it could be done. If that works for you, you could settle with it. The other option is to go up to a scope with more overall travel. The key here is that you’ll be making an informed decision and have a very good rough estimate of what you’ll be able to do with your rifle and a scope before you even buy it.

So, with a 100-yard zero, if we were to try and get that 22LR stretched out to 450 yards, well – we can’t. We don’t have enough cant. We needed 23.5 MRAD to get there, used up our 15 MRAD of adjustment we had left, and at 30x we’d have our 6 MRAD of holdover totaling 21 MRAD. We’d be 2.5 MRAD short. Of course, we could simply dial back the magnification to gain more holdover from the reticle, but we can’t do it at 30X. How do we hit our needed 23.5 MRAD then at 30X magnification if we want? Enter the canted scope base - In my case, 30 MOA almost got me there, and a 40 MOA would have with extra room. 

Hopefully this guide taught you something new and you can now apply some pretty simple math and concepts into your rifle setup and shooting to know what your equipment’s limitations are, and how to stretch them out further when you want to hit that new goal. Hopefully it also showed you how you can take a 22LR from 25 yards out to 450 yards – It’s with a bunch of cant, a scope with a healthy amount of elevation travel – and some calm wind.

-Bushnell Social Guy