Forum member Jacob spotted this simple, but effective set of scope ring inserts on the Brownells Website. With these inserts, you can use a scope with 1″-diameter main tube in 30mm rings. Non-marring, matte black Delrin sleeves surround the scope tube so it can fit larger-diameter rings. Each sleeve comes in two parts for easy installation around your scope tube. This way you can use the same 30mm rings for all your scopes.
Ring Reducers are sold as front/rear kits. Cost is $16.99 for the Delrin 30mm to 1″ converters, item 084-000-091WB. There are also sets that reduce 30mm rings to 26mm, and 1″ rings to 3/4″ or 7/8″.
Note: These Brownells units simply function as plastic bushings. Unlike Burris Signature Ring inserts, they do not allow you to “pre-load” windage or elevation. If your rings are misaligned, the Brownells Ring Reducers won’t correct that problem.
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A good riflescope is essential for many types of competition, and the vast majority of hunters have scoped rifles. Some F-Class and benchrest competitors are now using optics with up to 60X magnification. Over the past 30 years, scopes have continued to evolve with improved glass, more reticle types, vastly increased elevation travel, bigger main tubes, FFP and SFP options, and even built-in electronics.
When shopping for a riflescope, it’s useful to understand how scopes work — how the internal mechanisms control windage and elevation, how parallax controls work, and how magnification levels are controlled.
Basics of How Riflescopes Work
This Burris video (above) covers the key aspects of scope function: zoom magnification, windage control, elevation control, parallax control (front or side mount), and ocular lens focus. There are some tips on getting a new scope running smoothly — it’s wise to rotate the power control a few times as well as both windage and elevation knobs. The video below also explains how to set ocular focus controls optimally.
Scope Break-In Methods and Diagnosing Issues — Great Video
We recommend that all serious shooters watch this video start to finish. A very knowledgeable scope engineer, Leupold’s Mike Baccellieri, explains the fine details of scope operation — with very useful recommendations on how to ready a new scope for use (See 36:50 time-mark). With a new optic he advises to run the controls multiple times to full travel. Also, take your time to get the diopter control just right (See 26:40 time-mark).
The video also explains why, with a new scope or one that hasn’t been used much, it is sometimes effective to rotate the elevation PAST the desired setting then come back a click (See 35:40 time-mark). In addition, near the end of the video, the expert explains how you can use a mirror to determine if the scope mount (base and/or rings) is NOT aligned with the bore axis, forcing excess travel to get on target (See 42:00 time-mark). We have seen this caused by scope rails attached slightly off axis.
Large diameter turrets make windage and elevation markings easier to see, and the click “feel” may be more noticeable given the greater diametrical travel between clicks.
First Focal Plane (FFP) vs. Second Focal Plane (SFP)
The main visual difference between First Focal Plane (FFP) and Second Focal Plane (SFP) scopes is the appearance of the reticle (and its hash marks) at different magnification levels. With a FFP scope, the reticle increases in visible size (and line thickness) with increased magnification. This is so the angular hash marks remain constant (in Mils or MOA angular span) at all magnification levels. So, on a 10-30X FFP scope, a 0.1 Mil hash mark represents the SAME angular measurement at 10X, 20X, or 30X (or any magnification). The downside of the FFP system is that the reticle lines can appear very thick at high magnification. But for a PRS/NRL match, with targets at multiple distances, it is important that the hash marks represent the same angular measurement at all power settings.
On a Second Focal Plane (SFP) scope, by contrast, the reticle lines (and hash marks) appear visually (in thickness) the same at all magnification levels. This means the hash mark divisions will only be precise at one magnification level, as designed by the manufacturer. For example, you could have exact 1 MOA Hash marks at 10X. But zoom the scope to 20X and the same reticle hash mark would then cover 2 MOA. SFP scopes are popular with competition shooters who shoot at specific known distances. Not having thick reticle lines at 25X to 50X is an advantage when aiming at precise benchrest and F-Class targets.
ZEISS now makes excellent FFP Scopes with both MOA and Milrad options
Minute of Angle (MOA) vs. Milliradian (MILRAD or MIL)
This video also explains MOA vs. MRAD (Milliradian) controls. A Minute of Angle (MOA) is an angular measurement that represents 1.047″ at 100 yards. Modern MOA scopes are typically configured with 1/4 MOA or 1/8 MOA clicks. A Milliradian (MRAD) is another angular measurement defined as one-thousandth of a radian. Milrad scopes are commonly configured with 0.1 Milrad clicks. How much is a 0.1 mil at 100 yards? One mil equals 3.6 inches at 100 yards; therefore, 1/10th of that, 0.1 Mil, equals 0.36” – roughly a third of an inch – at 100 yards. That’s pretty close to the common quarter-inch (1/4 MOA) increment found on MOA riflescopes.
Sightron makes excellent high-magnification SFP zoom scopes favored by many competitors. These have proven quite reliable and offer very good performance for the price.
Scope Mounting Method and Alignment
When mounting a scope, you want to make sure the scope is aligned properly, so that vertical travel is precisely up and down, not offset. Begin by supporting the rifle with a good front and rear rest. Use a portable level to ensure the rifle is not tilting slightly left or right around the barrel bore axis. Then you want to align your scope’s vertical axis. For this, we recommend setting up a plumb bob — a weighted line that hangs straight down. This can be set up indoors or outdoors. Align your reticle’s vertical axis precisely with the plumb bob line, making sure not to move the rifle.
One caution — we have seen some riflescopes that are internally off-axis by up to 4 degrees. In this case, you can align the reticle’s vertical axis with the plumb bob line but then find that your turrets are slightly titled. That is a scope manufacturing fault that will result in some error when you input a large click value (e.g. 10+ MOA up or down).
When mounting your scope, a key factor to consider is the eye relief — the distance of the rear “ocular” lens to your eye. When mounting the scope, put your head in the position at which you normally shoot. NOTE: As your optimal head position may be quite a bit different when shooting prone vs. shooting from a bench, you may want to adjust the scope placement for different shooting positions. This Editor had to move his comp rifle scope about an inch rearward when local club matches changed from prone to bench.
Video collection suggested by Boyd Allen
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Many guys getting started in long range shooting are confused about what kind of scope they should buy — specifically whether it should have MIL-based clicks or MOA-based clicks. Before you can make that decision, you need to understand the terminology. This article, with a video by Bryan Litz, explains MILS and MOA so you can choose the right type of scope for your intended application.
You probably know that MOA stands for “Minute of Angle” (or more precisely “minute of arc”), but could you define the terms “Milrad” or “MIL”? In a helpful video, Bryan Litz of Applied Ballitics explains MOA and MILs (short for “milliradians”). Bryan defines those terms and explains how they are used. One MOA is an angular measurement (1/60th of one degree) that subtends 1.047″ at 100 yards. One MIL (i.e. one milliradian) subtends 1/10th meter at 100 meters; that means that 0.1 Mil is one centimeter (1 cm) at 100 meters. Is one angular measurement system better than another? Not necessarily… Bryan explains that Mildot scopes may be handy for ranging, but scopes with MOA-based clicks work just fine for precision work at known distances. Also because one MOA is almost exactly one inch at 100 yards, the MOA system is convenient for expressing a rifle’s accuracy. By common parlance, a “half-MOA” rifle can shoot groups that are 1/2-inch (or smaller) at 100 yards.
What is a “Minute” of Angle?
When talking about angular degrees, a “minute” is simply 1/60th. So a “Minute of Angle” is simply 1/60th of one degree of a central angle, measured either up and down (for elevation) or side to side (for windage). At 100 yards, 1 MOA equals 1.047″ on the target. This is often rounded to one inch for simplicity. Say, for example, you click up 1 MOA (four clicks on a 1/4-MOA scope). That is roughly 1 inch at 100 yards, or roughly 4 inches at 400 yards, since the target area measured by an MOA subtension increases with the distance.
MIL vs. MOA for Target Ranging
MIL or MOA — which angular measuring system is better for target ranging (and hold-offs)? In a recent article on his PrecisionRifleBlog.com website, Cal Zant tackles that question. Analyzing the pros and cons of each, Zant concludes that both systems work well, provided you have compatible click values on your scope. Zant does note that a 1/4 MOA division is “slightly more precise” than 1/10th mil, but that’s really not a big deal: “Technically, 1/4 MOA clicks provide a little finer adjustments than 1/10 MIL. This difference is very slight… it only equates to 0.1″ difference in adjustments at 100 yards or 1″ at 1,000 yards[.]” Zant adds that, in practical terms, both 1/4-MOA clicks and 1/10th-MIL clicks work well in the field: “Most shooters agree that 1/4 MOA or 1/10 MIL are both right around that sweet spot.”
Keith Glasscock is one of America’s greatest F-Class shooters, as well as a highly respected wind coach. A High Master, Keith finished second overall at the 2021 NRA F-Class Long Range Championship in F-Open division. He also finished second at the 2020 F-Open Nationals, and second at the 2019 F-Open Nationals. His consistency is unrivaled, which means he definitely knows the secrets of competition shooting and loading ultra-accurate ammo. Recently Keith has started PRS/NRL competition, bringing his shooting skills to those popular tactical disciplines.
Keith has a great YouTube Channel with new content every week. On Keith’s Winning in the Wind channel, Keith offers 235+ informative videos on a wide range of topics including wind reading, reloading, component selection, load development, and training.
For today’s Saturday Video Showcase, we offer eight of our favorite Keith Glasscock videos. These cover many key topics — ballistics, barrel care, gunsmithing, bullet sorting, reloading, maintenance and more. Each video has important points that can benefit any competitive rifle shooter, whether you shoot in local 100-yard fun matches or compete at the National Level in F-Class, LR Benchrest, Palma, High Power, or PRS/NRL.
For most disciplines, if you want to achieve maximum accuracy and consistency, you should have your action bedded. This provides an optimal “seating” for the action which quells shot-to-shot motion and helps reduce vibration. Gunsmiths say a good bedding job can produce immediate benefits. In this video Keith Glasscock explains how to check your stock bedding and discusses the realistic benefits you can expect in group size and consistency over long strings.
Keith Glasscock is one of the very few PRS/NRL competitors who has shot F-Class at the very highest level, finishing second three times in F-Class National Championships. PRS/NRL and F-Class are very different disciplines with different challenges. F-Class is shot prone with time between shots and target distances from 600 to 1000 yards. In PRS/NRL competition, you are shooting from multiple positions, at many distances from 100 yards on out, with fast follow-up shoots. For F-Open, you want an extremely accurate load that can deliver sub-quarter MOA groups at 200 yards. For PRS/NRL you don’t necessarily need that level of accuracy (though it helps). But you also need a load that is very consistent, has relatively low recoil, but can also provide sufficient impact energy to clearly show a hit on distant steel. In this video, Keith Glasscock explains his reloading objectives for the two disciplines.
Hard carbon is the bane of rifle shooters. Hard carbon build-up in the barrel can adversely affect accuracy, and in extreme cases, can lead to increased pressure. If possible, you should clean your barrel(s) soon after a match (or shooting session) before the carbon fully hardens. We’ve used Wipe-Out Foam right after a match (with an hour soak time) and that dramatically reduced the amount of brushing required. In this video Keith Glasscock explains the negatives of hard carbon in your barrel, and he discusses how to diagnose the problem and how to remove the carbon build-up efficiently.
Benchrest and F-Class shooters don’t worry about magazines, because their rifles typically employ single-shot actions. However, with PRS/NRL rifles you’ll be shooting from a magazine. Likewise many hunting rifles use magazines to enable quick follow-up shots. In selecting the best magazine(s) for your rifle and discipline you need to consider a variety of factors including fit, capacity, reliability, and, yes, cost. In this video Keith Glasscock examines a variety of magazines for bolt-action rifles used in PRS/NRL competition as well magazines for hunting rifles.
Barrel break-in is a controversial subject. With premium finish-lapped barrels from top manufacturers, some ace F-Class shooters get away with hardly no break-in — just shoot for score right from the get-go. On high-quality custom barrels, we’ve had success with minimalistic break-in with a few wet patches ever 3 rounds for the first 20 rounds. However, with relatively rough factory barrels, you may get better long-term results with a systematic break-in process, even using specialized products on your patches. In this video Keith Glasscock explains break-in procedures he’s found to work for various barrel types and applications.
In general, we have gotten the best match results with loads showing an Extreme Spread (ES) under 13 FPS and an extremely low Standard Deviation (SD). We know that F-Class and ELR shooters competing at 1000 yards and beyond definitely want an extremely low ES to minimize vertical dispersion at long range. That said, some short-range Benchrest competitors look at group size more than ES/SD. In this video, Keith Glasscock talks about the reloading process and methods for lowering ES and SD. Proper brass prep is important, as is precise powder measuring. And long range shooters may want to test 3 or 4 different powder types to find the one that offers the best combination of accuracy and low ES/SD.
Should you sort your bullets? If so, should you sort by weight, OAL, base-to-ogive, or max diameter? Which factor? Well the answer is “it depends”. You need to carefully examine a couple dozen bullets from each batch to see how consistent they are. We had some Lapua bullets that were ultra-consistent with 97 out of 100 within .0015″ base to ogive length. We used those bullets unsorted to set a local range record at 600 yards. On the other hand if you find significant differences in weights, diameters, or bearing surface lengths, you probably should sort. One tip — many shooters do not consider the width difference in bullets. We have seen 6mm bullet diameters vary from 0.2428″ to 0.2436″. We have one 3-groove 6BR barrel that likes the skinny bullets and another 6-groove barrel that definitely prefers the fatter bullets.
The Kestrel 5700 Elite Wind Meter boasts sophisticated ballistics capabilities and LiNK Bluetooth connectivity. With the Kestrel 5700 Elite, once you enter data about bullet type (and BC), velocity, zero, and rifle, the Kestrel can calculate come-ups and wind corrections. The Kestrel 5700 can “talk” to a mobile device that runs the Applied Ballistics APP that contains bullet databases and allows you to easily enter key information such as muzzle velocity, bullet BC, zero distance, velocity, wind, and environmental factors. In this video Keith Glasscock explains the Kestrel 5700’s features including the ability to program sectors for a PRS/NRL match.
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Burris Signature Rings with polymer inserts are an excellent product. The inserts allow you to clamp your scope securely without ring marks. Moreover, using the matched offset inserts you can “pre-load” your scope to add additional elevation. This helps keep the scope centered in its elevation range while shooting at long range. Additionally, with a -20 insert set in the front and a +20 insert set in the rear, you may be able to zero at very long ranges without using an angled scope base — and that can save money. (To move your point of impact upwards, you lower the front of the scope relative to the bore axis, while raising the rear of the scope.)
Insert Elevation Values and Ring Spacing
People are sometimes confused when they employ the Burris inserts. The inset numbers (-10, +10, -20, +20 etc.) refer to hundredths of inch shim values, rather than to MOA. And you need the correct, matched top/bottom pair of inserts to give you the marked thousandth value. Importantly, the actual amount of elevation you get with Burris inserts will depend BOTH on the insert value AND the spacing between ring centers.
Forum member Gunamonth has explained this in our Shooters’ Forum:
Working with Burris Signature Rings
Burris inserts are [marked] in thousandths of an inch, not MOA. To know how many MOA you gain you also need to know the ring spacing. For example, with a -20 thou insert set in the front and a +20 thou insert set in the rear, if the ring spacing is 6″, the elevation change will be approximately +24 MOA upwards.
Here’s how we calculate that. If you have a 2 X 0.020″ “lift” over a distance of 6 inches (i.e. 0.040″ total offset at 0.5 feet) that’s equivalent to 0.080″ “lift” over 12 inches (one foot). There are 300 feet in 100 yards so we multiply 0.080″ X 300 and get 24″ for the total elevation increase at 100 yard. (Note: One inch at 100 yards isn’t exactly a MOA but it’s fairly close.)
Here’s a formula, with all units in inches:
Total Ring Offset
——————– X 3600 = Change @ 100 yards
Ring Spacing
(.020 + .020)
—————– X 3600 = 24 inches at 100 yards
Ring Spacing: 6 inches
NOTE: Using the above formula, the only time the marked insert offset will equal the actual MOA shift is when the center to center ring spacing is 3.60″. Of course, you are not required to use 3.60″ spacing, but if you have a different spacing your elevation “lift” will be more or less than the values on the inserts.
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Based on its external appearance, a modern riflescope may seem simple. It’s just a tube with two or three knobs on the outside right? Well, looks can be deceiving. Modern variable focal-length optics are complex systems with lots of internal parts. Modern scopes, even ‘budget’ optics, use multiple lens elements to allow variable magnification levels and parallax adjustment.
A few seasons back, we had a chance to look inside a riflescope thanks to a product display from ATK, now called Vista Outdoor, parent of Alliant Powder, CCI, Federal, RCBS, Speer, Weaver Optics. The Weaver engineers sliced open a Weaver Super Slam scope so you can see the internal lens elements plus the elevation and windage controls. We thought readers would like to see the “inner workings” of a typical modern rifle scope, so we snapped some pictures. The sectioned Super Slam scope was mounted inside a Plexiglas case, making it a bit hard to get super-sharp images, but you can still see the multiple lenses and the complex windage and elevation controls.
Check out the details of the focusing and magnification rings near the ocular (eyeball) end of the scope. There is very fine machining and threading to make everything work properly. The ocular lens is the piece of glass that faces the shooter while he aims.
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In a helpful NSSF video, Ryan Cleckner explains why you normally should avoid canting your rifle — rotating it clockwise or counter-clockwise. Cleckner explains that canting the rifle in one direction or another will change the point of impact: “When you rotate the rifle, not only does the [POI move] in the direction that you’re rotated, [but] it also loses some of its elevation as it rolls down.” This, Cleckner explains, can make you miss on one side or the other:
Cant to the Left — You’re going to miss low and left.
Cant to the Right — You’re going to miss low and right.
In this video, starting at the one-minute mark, Cleckner shows the effect of rifle canting when engaging a 600-yard target. A few degrees of cant (either to the left or to the right), moves the shot POI completely off the steel silhouette target. The POI change occurs mainly because you are lowering (and laterally shifting) the scope sight-line relative to the bore axis, effectively changing your zero.
David Tubb has explained: “Every 1 degree you are off on a cant, is about six inches of difference laterally at 1000 yards”.
Position Shooting with Sling — Rifle Cant Considerations
Cleckner’s discussion assumes that the scope or sights are set to hit center with the rifle level and plumb. That works for most situations when shooting prone off bipod, front mechanical rest, or front sandbag. However, many sling shooters, including David Tubb and John Whidden, do tilt or cant their rifles slightly inward because this allows a more comfortable hold with sling, or allows better eye-to-sight alignment. Holding the rifle at an angle can work — but the angle of cant must be consistent for every shot. Canting the rifle is not a sin by itself. However, after you confirm your zero on your target, the degree of cant must be the same for EVERY shot. You must maintain that exact same degree of rotation on each shot or you will experience the shot POI movement Cleckner illustrates. Consistency is the key.
John Whidden, 5-time Nat’l Long Range Champion, holds a Palma rifle. John now shoots a match rifle with an Anschutz stock which he holds more upright, but still with some counter-clockwise cant. John also installed his iron sights at an angle so that the adjustments are correct (and plumb) even with his canted hold: “While it may not be obvious in the picture, the sights on my rifle are set up so that they’re straight vertical and horizontal while I hold the rifle canted. Making sure your adjustments (scope or sights) are vertical and horizontal is a critical piece of the pie.”
Inexpensive Dual-Diameter Scope-Mounted Bubble Level
The best way to avoid inconsistent rifle canting is to use a bubble level fitted to rail or scope. One very affordable and versatile product is the Jialitte Scope Bubble Level. This features a 30mm milled inside diameter, plus an inner insert ring so it will also fit 1″-diameter main tubes. The Jialitte unit is nicely radiused, and has a low profile in the middle. User reviews have been very positive. You could easily pay $35.00 or more for a 30mm scope level. This costs just $9.99 on Amazon.
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What is Parallax?
Parallax is the apparent movement of the scope’s reticle (cross-hairs) in relation to the target as the shooter moves his eye across the exit pupil of the riflescope. This is caused by the target and the reticle being located in different focal planes.
Here’s a good explaination of scope parallax. This video has been watched over 790,000 times.
Why is it Important?
The greater the distance to the target and magnification of the optic, the greater the parallax error becomes. Especially at longer distances, significant sighting error can result if parallax is not removed.
How to Remove Parallax
This Nightforce Tech Tip video quickly shows how to remove parallax on your riflescope.
While keeping the rifle still and looking through the riflescope, a slight nod of the head up and down will quickly determine if parallax is present. To remove parallax, start with the adjustment mechanism on infinity and rotate until the reticle remains stationary in relation to the target regardless of head movement. If parallax has been eliminated, the reticle will remain stationary in relation to the target regardless of eye placement behind the optic.
A varmint shooter’s target is not conveniently placed at a fixed, known distance as it is for a benchrester. The varminter must repeatedly make corrections for bullet drop as he moves from closer targets to more distant targets and back again. Click HERE to read an interesting Varmint Forum discussion regarding the best method to adjust for elevation. Some shooters advocate using the scope’s elevation adjustments. Other varminters prefer to hold-over, perhaps with the assistance of vertical markers on their reticles. Still others combine both methods–holding off to a given yardage, then cranking elevation after that.
Majority View — Click Your Scope
“I zero at 100 yards — I mean really zero as in check the ballistics at 200 and 300 and adjust zero accordingly — and then set the scope zero. For each of my groundhog guns I have a click chart taped into the inside of the lid of the ammo box. Then use the knobs. That’s why they’re there. With a good scope they’re a whole lot more accurate than hold-over, with or without hash marks. This all assumes you have a good range finder and use it properly. If not, and you’re holding over you’re really just spraying and praying. Try twisting them knobs and you’ll most likely find that a 500- or 600- or 700-yard groundhog is a whole lot easier than some people think.” — Gunamonth
“I have my elevation knob calibrated in 100-yard increments out to 550. Range-find the critter, move elevation knob up…dead critter. The problem with hold-over is that it is so imprecise. It’s not repeatable because you are holding over for elevation and for wind also. Every time you change targets 50 yards, it seems as if you are starting over. As soon as I got completely away from the hold over method (I used to zero for 200), my hit ratios went way up.” — K. Candler
“When I first started p-dog shooting, I attempted to use the hold-over method with a 200-yard zero with my 6mm Rem. Any dog much past 325-350 yards was fairly safe. I started using a comeups table for all three of my p-dog rifles (.223 Rems and 6mm Rem). 450-yard hits with the .223s are fairly routine and a 650-yard dog better beware of the 6mm nowadays. An added benefit (one I didn’t think of beforehand) with the comeups table (elevation only), is that when the wind is blowing, it takes half of the variables out of the equation. I can concentrate on wind, and not have to worry about elevation. It makes things much more simple.” — Mike (Linefinder).
“I dial for elevation and hold for wind. Also use a mil-dot reticle to make the windage holds easier. For windage corrections, I watch for the bullet strike measure the distance it was “off” with the mil-dot reticle, then hold that much more the other way. Very fast once you get used to it.” — PepeLP
Minority View — Hold-Over is Better
“I try to not touch my knobs once I’m zeroed at 200 meters. Most of my varmint scopes have duplex reticles and I use the bottom post to put me on at 300 meters versus turning knobs. The reason I try to leave my knobs alone is that I have gone one complete revolution up or down [too far] many times and have missed the varmint. This has happened more than once and that is why I try not to change my knobs if at all possible.” — Chino69
“I have been using the hold over method and it works for me most of the time but the 450 yards and over shots get kinda hard. I moved to a 300 yard zero this year and it’s working well. I do want to get into the click-up method though; it seems to be more fool-proof.” — 500YardHog
Compromise View — Use Both Methods
“I use both [methods] as well — hold over out to 250, and click up past that.” — Jack (Wolf)
“I use the target knobs and crank-in elevation. I also use a rangefinder and know how far away they are before I crank in the clicks. I have a scope with drop dots from Premier Recticle and like it. No cranking [knobs] out to 600.” –Vmthtr
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Many guys getting started in long range shooting are confused about what kind of scope they should buy — specifically whether it should have MIL-based clicks or MOA-based clicks. Before you can make that decision, you need to understand the terminology. This article, with a video by Bryan Litz, explains MILS and MOA so you can choose the right type of scope for your intended application.
You probably know that MOA stands for “Minute of Angle” (or more precisely “minute of arc”), but could you define the terms “Milrad” or “MIL”? In a helpful video, Bryan Litz of Applied Ballitics explains MOA and MILs (short for “milliradians”). Bryan defines those terms and explains how they are used. One MOA is an angular measurement (1/60th of one degree) that subtends 1.047″ at 100 yards. One MIL (i.e. one milliradian) subtends 1/10th meter at 100 meters; that means that 0.1 Mil is one centimeter (1 cm) at 100 meters. Is one angular measurement system better than another? Not necessarily… Bryan explains that Mildot scopes may be handy for ranging, but scopes with MOA-based clicks work just fine for precision work at known distances. Also because one MOA is almost exactly one inch at 100 yards, the MOA system is convenient for expressing a rifle’s accuracy. By common parlance, a “half-MOA” rifle can shoot groups that are 1/2-inch (or smaller) at 100 yards.
What is a “Minute” of Angle?
When talking about angular degrees, a “minute” is simply 1/60th. So a “Minute of Angle” is simply 1/60th of one degree of a central angle, measured either up and down (for elevation) or side to side (for windage). At 100 yards, 1 MOA equals 1.047″ on the target. This is often rounded to one inch for simplicity. Say, for example, you click up 1 MOA (four clicks on a 1/4-MOA scope). That is roughly 1 inch at 100 yards, or roughly 4 inches at 400 yards, since the target area measured by an MOA subtension increases with the distance.
MIL vs. MOA for Target Ranging
MIL or MOA — which angular measuring system is better for target ranging (and hold-offs)? In a recent article on his PrecisionRifleBlog.com website, Cal Zant tackles that question. Analyzing the pros and cons of each, Zant concludes that both systems work well, provided you have compatible click values on your scope. Zant does note that a 1/4 MOA division is “slightly more precise” than 1/10th mil, but that’s really not a big deal: “Technically, 1/4 MOA clicks provide a little finer adjustments than 1/10 MIL. This difference is very slight… it only equates to 0.1″ difference in adjustments at 100 yards or 1″ at 1,000 yards[.]” Zant adds that, in practical terms, both 1/4-MOA clicks and 1/10th-MIL clicks work well in the field: “Most shooters agree that 1/4 MOA or 1/10 MIL are both right around that sweet spot.”
In a helpful NSSF video, Ryan Cleckner explains why you normally should avoid canting your rifle — rotating it clockwise or counter-clockwise. Cleckner explains that canting the rifle in one direction or another will change the point of impact: “When you rotate the rifle, not only does the [POI move] in the direction that you’re rotated, [but] it also loses some of its elevation as it rolls down.” This, Cleckner explains, can make you miss on one side or the other:
Cant to the Left — You’re going to miss low and left.
Cant to the Right — You’re going to miss low and right.
In this video, starting at the one-minute mark, Cleckner shows the effect of rifle canting when engaging a 600-yard target. A few degrees of cant (either to the left or to the right), moves the shot POI completely off the steel silhouette target. The POI change occurs mainly because you are lowering (and laterally shifting) the scope sight-line relative to the bore axis, effectively changing your zero.
David Tubb has explained: “Every 1 degree you are off on a cant, is about six inches of difference laterally at 1000 yards”.
Position Shooting with Sling — Rifle Cant Considerations
Cleckner’s discussion assumes that the scope or sights are set to hit center with the rifle level and plumb. That works for most situations when shooting prone off bipod, front mechanical rest, or front sandbag. However, many sling shooters, including David Tubb and John Whidden, do tilt or cant their rifles slightly inward because this allows a more comfortable hold with sling, or allows better eye-to-sight alignment. Holding the rifle at an angle can work — but the angle of cant must be consistent for every shot. Canting the rifle is not a sin by itself. However, after you confirm your zero on your target, the degree of cant must be the same for EVERY shot. You must maintain that exact same degree of rotation on each shot or you will experience the shot POI movement Cleckner illustrates. Consistency is the key.
John Whidden, 5-time Nat’l Long Range Champion, holds a Palma rifle. John now shoots a match rifle with an Anschutz stock which he holds more upright, but still with some counter-clockwise cant. John also installed his iron sights at an angle so that the adjustments are correct (and plumb) even with his canted hold: “While it may not be obvious in the picture, the sights on my rifle are set up so that they’re straight vertical and horizontal while I hold the rifle canted. Making sure your adjustments (scope or sights) are vertical and horizontal is a critical piece of the pie.”
Inexpensive Dual-Diameter Scope-Mounted Bubble Level
The best way to avoid inconsistent rifle canting is to use a bubble level fitted to rail or scope. One very affordable and versatile product is the Jialitte Scope Bubble Level. This features a 30mm milled inside diameter, plus an inner insert ring so it will also fit 1″-diameter main tubes. The Jialitte unit is nicely radiused, and has a low profile in the middle. User reviews have been very positive. You could easily pay $35.00 or more for a 30mm scope level. This costs just $8.79 on Amazon (Cyber Monday special).
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We first ran this article in 2012, and it was very well received. Since then, many Forum members have requested an explanation of MILS and mildots, so we decided to run this feature again…
1 Milliradian (Milrad or ‘Mil’) = 1/1000th of a radian | 1 Milliradian = 0.0573 degrees.
In this NSSF Video, Ryan Cleckner, a former Sniper Instructor for the 1st Ranger Battalion, defines the term “MilliRadian” (Milrad) and explains how you can use a mildot-type scope to range the distance to your target. It’s pretty simple, once you understand the angular subtension for the reticle stadia dots/lines. Cleckner also explains how you can use the milrad-based reticle markings in your scope for elevation hold-overs and windage hold-offs.
Even if you normally shoot at known distances, the hold-off capability of milrad-reticle scopes can help you shoot more accurately in rapidly-changing wind conditions. And, when you must engage multiple targets quickly, you can use the reticle’s mil markings to move quickly from one target distance to another without having to spin your elevation turrets up and down.
WEB RESOURCES: If you want to learn more about using Milliradians and Mildot scopes, we suggest the excellent Mil-dot Explained article from targettamers.com Guide. This covers the basics you need to know, with clear illustrations.
Also informative is The Truth about Mil Dots by Michael Haugen. Mr. Haugen begins with basic definitions: 360 degrees = 2 x Pi (symbol π) Radians. That means 1 Radian is about 57.3 degrees. 1 Milliradian (Milrad or ‘Mil’) = 1/1000th of a radian. Thus 1 Milliradian = .0573 degrees.
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Forum member Jacob spotted this simple, but effective set of scope ring inserts on the Brownells Website. With these inserts, you can use a scope with 1″-diameter main tube in 30mm rings. Non-marring, matte black Delrin sleeves surround the scope tube so it can fit larger-diameter rings. Each sleeve comes in two parts for easy installation around your scope tube. This way you can use the same 30mm rings for all your scopes.
Keith has a great 
A varmint shooter’s target is not conveniently placed at a fixed, known distance as it is for a benchrester. The varminter must repeatedly make corrections for bullet drop as he moves from closer targets to more distant targets and back again. 
Minority View — Hold-Over is Better
In this NSSF Video, Ryan Cleckner, a former Sniper Instructor for the 1st Ranger Battalion, defines the term “MilliRadian” (Milrad) and explains how you can use a mildot-type scope to range the distance to your target. It’s pretty simple, once you understand the angular subtension for the reticle stadia dots/lines. Cleckner also explains how you can use the milrad-based reticle markings in your scope for elevation hold-overs and windage hold-offs.
