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How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Ever had a scope you just couldn’t get properly sighted in? Assuming your rifle and ammo are good, start with the scope, rings and bases to isolate and solve the problem.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Recoil is hard on scopes and mounting systems. Particularly, heavy recoilers such as this .416 Ruger. Vibration in airplanes and behind truck seats and on ATVs also often causes loose mounts and rings. Mount your scope properly and check it often to ensure it will perform at the moment of truth.

Once, on the way into remote desert mountains in southern Arizona, I paused to check the zero of my lightweight custom mountain rifle. I’d flown to Tucson with the rifle, and wanted to be sure I was prepared to make a clean, precise shot on a tiny-bodied coues deer buck.

To my frustration, I found the rifle hit way off. As in, a foot to the right at 100 yards. Worse, it wouldn’t shoot small groups, and I couldn’t get the scope to adjust properly and hold zero. It was a Zeiss; a premium optic that should be consistent and reliable.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

A common cause of ring and base failure is loose screws. Check them frequently to ensure they stay tight.

Finally, a full box of ammo into the ordeal, I put on my forensics cap and began examining the rifle. I confirmed that the action bolts were torqued properly. I checked that the scope ring screws were as well. Lastly, I went to the scope bases—and found the problem. One of the side-mounted screws that clamps the rear ring in place had come loose. No wonder my point of impact had been way to one side.

Once that screw was tightened, the rifle produced its customary small groups, and the scope held zero perfectly.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Heavy scopes are especially hard on rings and bases. It’s smart to use one-piece systems that eliminate weak links in the system.

The inability to get a rifle sighted in can come from several sources. Your rifle could have a problem. Or it just may not like the loads you’re feeding it. It could—(shocking thought!)—even be you, the shooter, that’s inconsistent. However, scope and scope mounting-system issues are frequently the culprit, and that’s what we’re here to explore in this article.

When you think about it, riflescopes and the rings that hold them in place are rather amazing creations. It’s surprising that anything could hold a glass telescope with many moving parts in place while a controlled explosion and a whole bunch of Newton’s Law occurs inside the rifle that scope is mounted to.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Not all cartridges are created equal. Some, such as the .22 Long Rifle, .223 Remington, and 6.5 Creedmoor will never stress a scope. Others, such as the .416 Rem. Mag. and .458 Lott can break a cheap or improperly mounted one with just a few rounds.

Good bases and rings do hold quality scopes precisely in place. Not just for a while, but as hundreds, even thousands of shots create mini earthquakes.

However, some scopes just won’t hold zero, and some bases and rings just won’t hold tight. Usually, that’s because they’re either cheap (let’s call it what it is), or they’ve been improperly mounted.

Either is extremely frustrating. Both must be resolved before the rifle can perform properly.

What causes scopes, scope rings, or bases to come loose? There are a variety of possibilities, but the most common ones are recoil—when a scope is mounted improperly—and vibration. As in, vibration in the belly of an airplane, or the rifle case mounted to your ATV, or behind the seat of your pickup.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

The first check to perform on a suspected scope is to grab it and twist and crank on it. If you feel any movement at all, something is loose in the bases and/or rings. Elementary, yes; but useful in diagnosing significant problems.

Recoil, of course, is the primary suspect. When a cartridge ignites and the gunpowder inside explodes, thrusting the projectile from zero to Mach 2 or 3 in a nanosecond, there’s a whole lot of seismic activity going on. Up top, that scope full of glass and aluminum parts has to hang on, and what’s more, all those parts have to stay stable. Worst, there are several potential “weak links” between the scope and the rifle.

If your scope rings aren’t positioned properly and torqued properly, the scope can actually slide forward a fraction inside the rings each time the rifle recoils rearward.

If the rings are properly fit to the bases, repeated rearward recoil of the rifle can eventually loosen the joints.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Quality bases and rings, properly mounted, greatly minimize the possibility of recoil-related issues. The rings shown are high-end lightweight versions by Nightforce; the Leupold QRW bases are made of steel (much the best material for bases).

If the bases aren’t correctly mounted to the action, the same thing can occur: repeated recoil can jar screws loose. In extreme cases, substantial recoil (such as a .30-378 Weatherby, .458 Lott, or .470 Nitro Express) can sheer screws right off.

Simple, continued vibration, such as the gentle hum of an airplane, is most likely to just loosen screws. It’s relatively harmless in the grand scheme of things—unless it causes you to miss a giant buck or bull.

Identifying an issue usually begins with unpredictable point of impact and bigger-than-average groups. Once you suspect you have an issue, spend some time examining your rifle and scope mounting system. On more than one occasion when a friend was struggling with point of impact issues, I’ve grabbed the scope atop his rifle and given it a brisk twist; you’d be surprised how often it moves. And how disconcerted the shooter is when it does!

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

High-end scope rings are made of steel or machined aluminum. While separate rings and bases are common, the strongest systems incorporate the two. Examples are the Nightforce cantilever AR-appropriate one-piece system at left, and the Talley Lightweight Alloy rings at top right. Premium “tactical” type rings such as the others shown are the way to go if one-piece systems are not an option.

Twist on the scope, attempt to wiggle it forward and back, lift and press on the front and the rear, and so forth. You may feel a trace of movement.

Sometimes you uncover a distinct issue, as I did on my way into coues deer country. Other times, you have to work on suspicion, performing corrective action on the possibility that the optic system is at fault. Whether or not you pin the issue to the scope and/or mounts, making sure the optic is mounted correctly is one step toward eliminating all potential issues.

When performing corrective surgery on a riflescope and mounting system, it’s usually best to disassemble the entire system. This is particularly true when working without a known diagnosis.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

A tiny dab of Loctite on scope base and ring screws can save a whole lot of headaches down the road. Don’t over-do it.

Replace any cheap parts with premium-grade gear. This generally means steel bases, and rings by high-end manufacturers. Talley’s one-piece base/ring combinations made of aluminum are exceptional. Called the Lightweight Alloy Scope Mounts, they eliminate one weak link, are perfectly concentric, and superbly strong. Best of all, they don’t cost much. Nightforce’s X-Treme Duty Ultralight rings are a titanium alloy, and are exceptional—but expensive. For AR-type rifles, a one-piece cantilever-type mount eliminates several weak links and is absolutely the way to go.

Long ago while working in a Utah gunshop through college, I was taught to degrease all mounting screws and holes. The manager didn’t like battling Loctite when mounting a new scope for a customer, and degreased screws stayed tight.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

Finger-tighten base and ring screws first, working all slop out of the bases and getting the gap on each side of the rings even before torquing to final spec.

Then I moved to Los Angeles to work for Petersen Publishing for two years, after which I transferred to the new publishing headquarters in humid Illinois. All my degreased screws rusted. Rusted-up screws are harder to remove than those with Loctite, and, well, they’re rusty. Not cool. Loctite is a far better choice for securing screws.

With a dab of Loctite on the threads, finger-tighten each screw incrementally, wiggling and working the base to make sure it finds a correctly centered equilibrium. With all movement eliminated and the screws firmly finger tight, swap to your torque wrench (I use a $60 F.A.T. Wrench by Wheeler Engineering), and torque the screws to the manufacturer’s recommended spec.

Don’t overtighten screws. You can strip the threads from the holes in your rifle’s action, or sheer off a screw in the hole.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases
A torque wrench is an invaluable tool in performing correct scope mounting. It prevents you from stripping screw holes or sheering screws or distorting scope tubes, yet ensures you achieve maximum holding capability.

Lay your scope in the rings, place the ring upper halves, and start the screws—each with a dab of blue Loctite. Work out the correct eye relief and level up the scope. Incrementally snug the ring screws to finger tight, maintaining an even gap on each side where the upper and lower portions of the ring nearly meet.

Finally, tighten each rings’ screws in an “X” pattern—front right, rear left, front left, rear right, repeat—a bit at a time until the torque wrench clicks over on all of them.

Again, don’t overtighten. Torque on scope rings is surprisingly mild, usually in the realm of 17 to 20 inch pounds. Much tighter, and those rings can compress the aluminum scope tube, restricting the movement of the magnification zoom and turret adjustments inside.

How Rifle-Shot Recoil Affects Scopes, Rings and Bases

The final step in mounting your scope is to torque the ring screws to spec. With quality components, a bit of Loctite, and attention to detail when mounting, the possibility of scope base or ring failure is very small.

If you’re setting up a heavy-recoiling rifle, it’s worth lapping the inside of the rings to make them perfectly round (a topic for a different article), and dusting the inner surfaces with powdered rosin such as Scope Grip Rosin. For those unfamiliar, traditional rosin is a tacky derivative of sap. Violinists use it in solid form to treat their bows. Bull riders use powdered rosin to help their gloves stick to their bullropes. Savvy big-bore shooters use it to prevent scope slippage.

With quality bases and rings, correctly secured by screws treated with a dab of Loctite and properly torqued, a high-quality scope will stay put through thousands of rounds worth of recoil and thousands of miles in an airplane or pickup truck.

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Mildot Range Estimation by John McQuay

Range estimation is a key skill in the sniper’s toolbox. If you don’t know how far away your target is, you have little chance of hitting it on the first shot. One shot, one kill…right? There are many methods of locating the target’s range. For the purpose of this period of instruction we will be covering range estimation with the mildot reticle and it’s variants.

In years past the basic mildot reticle came in two flavors. You could either get round dots or “footballs”. In recent times the footballs have faded from existence. They have been replaced by a myriad of lines and circles and dots. The basic premise that we are going to demonstrate here will work for any milradian based reticle.


Mil Relation Formula
The core of rifle scope range estimation is a math problem referred to as the “Mil Relation Formula”. This takes the height of the target in inches, multiplies it by a constant and then divides by the number of mils read in the scope.

The basic formula looks like this:

Mil Formula

The 27.77 is a “constant”. This is sometimes expressed at 27.78, which is the mathematically correct rounded number. Most Marines will use 27.77 because that is what we were taught. Either will get you close enough to make a first round hit. Other formulas are available to convert range to meters or to start with the target height in a different unit of measure. I prefer this formula because it is easy to remember and uses units that most of us in the United States are familiar with.


Measuring with Mils
The hardest part of range estimation by the Mil Relation Formula is actually measuring the target. To be accurate you need to train your eye to measure to the nearest tenth or a mil or 0.1 mil. Most experienced snipers can measure down to five hundredths of a mil or 0.05. All it takes is practice.

First Focal Plane vs. Second Focal Plane:

Rifle scopes generally come in two varieties. The most common is the Second Focal Plane reticle. In this type the reticle covers more or less of the target depending on the magnification setting of the scope. If you are looking at a target through the rifle scope and you turn the power selector ring the reticle will appear to stay the same size as the target zooms larger. This causes a couple of problems. The first being that the reticle will only be accurate for ranging at one power setting. The second is that the reticle will only be correct for holds at one power setting.

First Focal Plane scopes have been gaining popularity in the US. They have the benefit of the reticle reading correctly at any power setting. When you look through the scope at a target and turn the power selector ring the reticle will appear to grow or shrink at the same rate as the target. The drawback to this is that the reticle thickness becomes a compromise. Too thick of a reticle will obscure too much of the target at high magnification. Too thin and it will become invisible at low power. The reticle also becomes easy to loose in the background on low power in low light unless it is illuminated.

Verifying the Reticle Scale:

Your first priority before using your Mil reticle is to verify that the scale reads correctly and at what power. This is a fairly simple exercise. First find a large piece of cardboard. Draw a vertical line on it with a heavy black marker. Using a very accurate ruler make horizontal hash marks across the vertical line every 3.6″. Be careful with your measuring. Set your cardboard at 100 yards and line the center of your reticle up with the bottom most hash mark on the cardboard. Each mil mark in your scope should line up with each hash mark on your cardboard. If you are using a mildot type scope then the hash marks should bisect the dots. If you are using a line type reticle like the GAP reticle then the hash marks should line up with the full mil hashes in the reticle.

What if it doesn’t line up? If your scope is a Second Focal Plane scope, then experiment with different power settings until you find the one that matches up. When you do, take a silver sharpie and make a mark across the ring and the scope body so that you can quickly locate the correct setting in the field. If your scope is a First Focal Plane and you are sure that you measured correctly when laying our your board, then you need to contact the manufacturer for warranty service.

Milling the Target.

Hopefully your scope came with literature showing the scale of the different portions of your reticle. In any Mil based reticle the center to center distance of the most prominent marks should be one mil. All other measurements are up for grabs.

Here are a couple of common reticles:

We will use the “Army” type Mildots for most of our examples. These are the most common and found in Leupold as well as many other makes of rifle scope. I am not aware of any new scopes using the USMC Mildot. I include them here on the odd chance someone comes across an old USMC scope.

To range a target to a tenth of a mil we need to build a stable position just like if we were going to send a shot downrange. Any tremor is going to cause problems.

Place the reticle over the target and count how many full mil increments there are.

In the image above we see that the Taliban fighter is 4 mils tall. Since our S2 briefed us that this selected target is 5’8″ (68″) we can plug these figures into our formula.
68 inches tall times 27.77 (our constant) divided by the number of mils the target measured in the scope (4). Crank that through your calculator and you see that our target is 472 yards away.

Now let’s make this a little more difficult.


In this image we can see that our innocent little friends are taking a stroll. Our loader is more than two and a half mils tall, but that’s not going to cut it.


If we look closely at where his foot falls above the third mill dot we can begin to break it down. With your minds eye, split that mildot in half. That half mildot measure 0.1 mil. Now you can’t quite fit that half mildot between his foot and the top of the whole mildot, so we break it down again. This gives us 0.05 mil. Now add that to the “half” mildot and we get 0.15 mil between the center of the dot and the bottom of our jihadist’s foot. If we subtract 0.15 mils from 1, we get 0.85 mils. Add back in the two mils above that and we get a measured height of 2.85 mils. Lets assume that our militant here is 64″ tall (from our intel reports). Let’s plug that into our formula.


If we didn’t go to the trouble of breaking it down and just rounded it to 3 mils we would have come up with 592.42 yards to target. In this case that would have resulted in an elevation error of about 12″ with M118LR. Breaking the dot down to .05 will give you improved accuracy but is not required for closer range targets.

When the target won’t stand still, or you do not know the height of your target you can use objects nearby. In the city this is pretty easy. Out in the woods it’s a bit more difficult. If you have several objects in your field of view, range the largest first. Larger targets will generally give you more accuracy. Ranging several targets and taking the average will also cut down your error. After time you may notice patterns to your errors. It’s good to note these so that in the future you can take them into account. A laser rangefinder is an excellent tool to have to confirm your calculations when you are learning to read mils.

If you are working with a spotter, both of you should do the calculations independently and then take the average.

Mildot ranging is an excellent skill, but is only as accurate as you are. It is also slow and difficult to use on moving tagets. In this a laser rangefinder excells. However, batteries die and electronics fail. Backup skills are nice to have.


Additional Formulas


Common Items

Item Size
Standard Doorway 36″ wide x 84″ tall
Basketball 9.75″
License Plate 12″ wide x 6″ tall
Speed Limit Sign 24″ x 30″
Yield Sign 36″
Wood Pallet 4′ x 4′
Paper (Letter Size) 8.5″ x 11″
Payphone 8.5″ x 21.5″

All dimensions are approximate and should be verified by the user. When possible it is a good idea for you to actually go out to the areas you work and measure common items. If you find yourself frequently in the same housing projects, then measure some windows and doors. They may come in handy some night if your LRF dies.


Other Reticles

GAP Reticle

This is my current personal favorite. It can be had in most of US Optics scopes. The reticle can be a bit confusing at first, but becomes second nature after use. The hash marks are .1 mil in thickness and are .5 mil across. The small hash marks are .25 mil across.

I use one in a USO SN-3 3.2-17x. It has allowed me to range targets to 1%.

Skeletal Mildot Reticle

This is more of a standard mildot reticle with skeletonized stadia lines. This reticle is found in the first generation Falcon Menace FFP scopes. The reticle works well at it’s highest power setting. When power is reduced the reticle becomes hard to see in dim light or w

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