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Long Range Shooting & Hunting - Page 2

Developing a Drop Chart

It is very important to know the muzzle velocity of the cartridge-bullet-rifle combination. Knowing the velocity is a key in developing an accurate bullet drop chart. It is essential to chronograph the particular load to be used. The same load fired in another rifle or barrel might not yield the same velocity. Also, most of the big game seasons, at least in my part of the world, are in the colder fall months. The actual chronographed muzzle velocity on a cold, 35-degree November day might be much different than the velocity of that same load fired on a hot July afternoon. It is not uncommon to have a 100 fps difference in velocities due to temperature changes. That amount is easily enough to cause a miss at long-range.

Determine Ballistic Coefficient

After the muzzle velocity is known, the appropriate ballistic coefficient for the bullet should be determined. All bullet manufacturers publish ballistic coefficients for their line of bullets. That value may or may not be the correct one to use however, for precise long-range work. Like prices on the window sticker of a new car, the numbers don't always say what they mean.

Sierra is the only manufacturer to use the multiple ballistic coefficient approach. They have determined through firing tests that the ballistic coefficients for their bullets change as the bullets go through different velocity zones. Actually, all bullets that have their coefficient based on the G1 drag function, and that have a shape different than the original model, have a ballistic coefficient that varies with velocity. This covers virtually all small arms bullets with a C1 ballistic coefficient. Generally speaking, the ballistic coefficient decreases in value as velocity decreases.

The use of computer trajectory programs, along with the use of chronographs, has been a tremendous aid in calculating bullet drop charts for long-range shooting. There are a number of programs available. I have experience with some of them. Probably any of these programs which include a bullet path computation could be used for this work.

If Sierra's trajectory program is used to compute bullet drop, it incorporates the multiple ballistic coefficient feature. Sierra's reloading manual lists the coefficients for each bullet through the velocity ranges. Two other programs that I have used with good success are one by ProWare and one by Tioga Engineering.

Of the Sierra bullets that I've used, the multiple ballistic coefficients seem to be accurate. This is based on actual observed bullet drop at long-range. The one exception to this is the 250 grain 30 caliber bullet. Sierra lists the coefficients for this bullet as .697 for velocities above 2600 fps, as .748 for 2250-2599 fps, as .777 for 1751-2249 fps, and as .743 for 1750 fps and less. My experience indicates that the ballistic coefficient is closer to the .697 value for all velocities. This was true at least in the barrel I fired them, shooting the bullets over two chronographs to determine ballistic coefficient. Actual drop figures also seem to indicate a coefficient of about .700. Sierra has replaced this bullet with a 240 grain version and its coefficient will be just a bit lower.

If the program being used to calculate drop does not have a multiple ballistic coefficient feature and Sierra bullets are being used, I'll pass on a tip I learned from Bill Davis of Tioga Engineering. He suggested that the correct coefficient to be used could be found by using the remaining velocity figures from Sierra's published trajectory data and running them through a computer program that calculates ballistic coefficient from two ranges and velocities. Sierra lists velocities on out to 1000 yards.

For example, if the bullet being used is the 220 grain 30 caliber version at a muzzle velocity of 3000 fps, the remaining velocity at 1000 yards is 1706 fps. This 1000 yard velocity is the same as if a .641 ballistic coefficient were being used in lieu of multiple ballistic coefficients. Sierra lists the coefficients of this bullet as .655 for 2400 fps and above. It is .630 between 1601 fps and 2399 fps, and for velocities less than 1600 fps it is .610. I have also used a dual chronograph setup and fired this bullet over it. I found the ballistic coefficient to be .640 at a muzzle velocity of 3100 fps. I have used this value, .640, in preparing drop charts for this bullet and found it to be just about right.

The ballistic coefficients for two other Sierra Match Kings used for long-range work, the 200 grain 30 caliber and the 168 grain 7 millimeter were also figured in this manner. They are .597 for the 30 caliber at a muzzle velocity of 3200 fps and .625 for the 7 millimeter bullet at 3200 fps. I have not shot either of these bullets enough to know how these figures bear out in actual shooting though.

The ballistic coefficients for Nosler's Ballistic Tip line of bullets seem to be quite useable for long-range work. As I mentioned earlier, I have not shot these bullets at long range as much as the Sierras. When I have, and used their ballistic coefficients, the drop figures seemed accurate.

Walt Berger's 210 grain .30 caliber VLD seems to have a ballistic coefficient about the same as the 220 grain Sierra Match King. This Berger bullet is another excellent long-range performer.

Now that the correct sea level ballistic coefficient is known, the atmospheric conditions for the shooting trip must be taken into consideration. In general terms, as altitude increases or local barometric pressure decreases, the density of the air decreases. Also, when air temperature increases, air density decreases. When the air is thinner than the standard sea level atmosphere, bullets will perform better. The bullet will drop less over a given range and the wind will blow it off course less. The amount of increased bullet performance can be simulated by assuming that it has a ballistic coefficient higher than its sea level value. It is the sea level ballistic coefficient that is listed by the bullet manufacturers.

A change in humidity also has an effect on air density, but it is very minor and can be ignored. Normally, it will change a ballistic coefficient by less than one percent. Contrary to popular belief, higher humidity actually decreases air density. Although it seems thicker to us mortals, for bullets and airplanes it is really slightly thinner.

Altitude has the biggest effect on air density, followed by changes in air temperature. When shooting in mountainous country, altitude changes should be taken into consideration. Temperature will usually decrease however, when altitude increases, each somewhat offsetting the other.

It should be noted that there are two basic methods that can be used to arrive at the correct ballistic coefficient for non-standard atmospheric conditions. Most trajectory computer programs have the capability of handling changes in altitude, and usually temperature changes as well. I know of just one that will also account for barometric pressure changes.

Fluctuations in the barometer can be easily simulated. An inch of change in barometric pressure is equivalent to an altitude change of 1000 feet. If the effects of lower barometric pressure is questioned, the altitude should be increased the appropriate amount. A higher pressure is simulated by decreasing altitude. For example if the barometer reads 30.35", the local pressure is .43" above standard, with 29.92" being standard (30.35 - 29.92 = .43). If the shooting site elevation is 3400 feet, the above standard pressure can be simulated by entering into the program or calculations an elevation of 2970 feet [ 3400 - (.43 x 1000)=2970 ]. With this approach, the program handles the math in the air density calculations. Letting the computer do the air density computations is the easy way. A disadvantage however is that not all of the programs allow both altitude and temperature inputs. And as I mentioned, only one considers barometric pressure.

The other method deals directly with the sea level coefficient before the computer program is used. If this route is chosen, the altitude input in the trajectory program should be zero for sea level and the temperature should be 59 degrees, standard for sea level.

For example if we have decided to use the 220 grain, thirty caliber Sierra bullet and a ballistic coefficient of .640, what would the equivalent ballistic coefficient be for an elevation of 4500 feet and a temperature of 50 degrees? Using the formulas for these variables, it would be .737. The bullet would perform as if this were its coefficient instead of .640. When entering the variables into the program, the correct coefficient to use would then be .737 and altitude zero. Temperature, if it is a variable, would be 59 degrees.

Uphill-Downhill Shooting

Shooting uphill or downhill will result in high shots if the angle is roughly 15 degrees or more or if the range is very long for lesser angles. The actual bullet drop is dependant on the true horizontal distance to the target not the slant range. Our range finders measure the slant range. Again there are several methods to determine the amount of correction necessary. Most, if not all, ballistic programs can take into account angled shooting and print out the correct drop for any range. The Sierra handloading manual in the exterior ballistics section deals with this subject with an example.

The Sierra manual has a table of factors that in use are multiplied by the total drop in inches, for the slant range to the target. The factors are .034 for 15 degrees, .134 for 30 degrees, and .293 for 45 degrees. There are more listed in the manual but these will give the reader an idea of the degree of change as the slope increases. Their use is simple. Let's say that you were looking uphill at a mule deer buck that your range finder said was 675 yards away. Looking at your drop chart you read that for that distance you need 11 1/2 minutes of adjustment in your scope. The catch though is the buck is uphill at an angle of 30 degrees. Using these factors we take the total drop for 675 yards (which is 103.1 inches) and multiply by .134 (the factor for 30 degrees) and the result is 13.8. That is to say that the bullet would impact about 14 inches high if we did not allow for the angle. Fourteen inches is about two minutes of angle at that distance. From this example we can see that it would be easy to miss that buck had we not taken into account the steep angle to the deer.

Generating Drop Chart

Now that we know the appropriate ballistic coefficient and the muzzle velocity for the bullet, it is a simple matter to run a drop chart from the computer program. Almost all the shooters I know base their charts on a 100 yard zero for the bullet. It is from this known zero that all scope corrections are made for longer shots. Target scope knobs are calibrated like a micrometer, so once the setting for zero is known, it is easy to return home. The drop chart might be as simple as the number of scope `clicks' required for each range or it might be a computer-generated minute of angle (or `MOA') correction for each range. Whatever is used, it must be a simple and fast system for putting the correct amount of adjustment into the scope knob. Emphasis on simple.

It is important when developing the drop chart to have the yardage intervals close enough together that the amount of correction between them is not too great. For example in the sample chart, the interval for the longer ranges is 20 yards apart. This spacing means only about one minute of change between yardages on the table. If the interval was much greater, a little reading between the lines might be required for some distances. The easier it is to use in the field, the better. A piece of advice VCR makers should learn.

I am familiar with just one program that will calculate the MOA correction needed for each range. This is the program from Tioga Engineering.

It is fairly easy though, to calculate the MOA correction from just the yardage and bullet path or bullet impact figures. For example, if the bullet path was 210.7 inches low at 1000 yards, the MOA correction is found by first multiplying the range in yards by .01047. The second step is to divide the bullet path figure by this number. Plugging in the numbers it would be 210.7 / (1000 x .01047) = 20.12 or 20.1 minutes of angle. Using a target scope with quarter minute clicks, this would be 80 clicks. Using the figure of .01047 above yields the true MOA value with one minute of angle being 1.047 inches at 100 yards.

The true MOA value should be used if the scope adjustments are calibrated for actual MOA. Not all scopes are. Surprisingly not all scopes from the same manufacturer are based on the same value. Almost all target scopes are calibrated so that one click is worth, nominally, one quarter minute of adjustment.

Another problem associated with internally adjustable scopes has to do with the click value changing as the adjustment reaches the outer limits of its travel. One click in the center range of adjustments may not be worth the same as one click 35 minutes of adjustment away. The only sure method I know to check for this condition is to measure off 300 feet and set up a tape measure or yard stick and start clicking the scope.

If the scope adjustments are not based on true MOA but some other figure, such as 1.000" at 100 yards, the actual MOA number can still be calculated. In the example above we multiplied the range in yards by .01047. If the clicks were based on 1.000" at 100 yards instead of 1.047", the range in yards should be multiplied by .01, not .01047. Other oddball click values can be similarly accounted for.

External adjustment scopes, such as the Unertl or Mitchell have an advantage over the internal variety in this regard. If the scope base blocks are spaced at 7.2", the clicks of a Unertl will be worth one quarter minute of adjustment. With any other spacing the click value falls into the oddball category. Another advantage of the Unertl type scopes is the fact that the shooter is always looking through the optical center of the scope, regardless of how many minutes of adjustment are dialed into it. This is not true of the internal type. At the extremes of adjustment, there is some optical distortion in the internals, and as mentioned above the click value may change.

Despite the advantages of the Unertl scopes, almost all of my own shooting has been with the internally adjustable Leupold and Night Force target scopes. These have usually been in 24 power for long-range work or one of the variables from Night Force.

In this section we have found then, to hit a target, an accurate drop chart with scope adjustment figures for each range, based on the individual scope's click value, is required. An accurate drop chart is generated by knowing the `correct' ballistic coefficient of the bullet for the given shooting conditions, and knowing the actual muzzle velocity of the bullet.

Long-Range Optics

This section will discuss the optical equipment used by the long-range shooter including more on scope choices. Perhaps more than any other type of shooting the long-range shooter relies on his optics, not only for shot placement but also for observing the target and determining its distance. There are then, three main categories of optics that the long-range shooter is interested in. The first includes binoculars and spotting scopes used in finding the target and spotting shots. The second category is the optical or laser rangefinders used in determining the exact distance to the target. The third is the rifle scope used on the big magnum rifles for precise shot placement.

Glassing for Mule Deer in the Missouri Breaks country of Montana.

Spotting Scopes and Binoculars

I have long been interested in binoculars and spotting scopes as well as most types of optical equipment. Over the years I have used quite a few different types and brands of scopes and binoculars. Until fairly recently, there were not many high-powered binoculars available, other than WWII-era Japanese battleship binoculars. Spotting scopes are wonderful for looking at or for something at long distances if you don't plan on looking for any length of time. When I squint through a spotting scope for very long though, my other eye starts to give me trouble. Soon I find myself going back to a pair of binoculars to get away from the eye fatigue associated with the single spotting scope.

There are two different ways to use binoculars and spotting scopes when hunting. Some short range hunters only use their binoculars to look at game animals after they have already spotted them with their unaided eyes. The long-range hunter, on the other hand, often spots his game only after using his optics. Whether or not you are a long-range hunter, this technique is an excellent way to spot game and then sneak up on it. Much more game will be seen using this technique. In the areas where I hunt in the mountains, we usually glass open parks and older clearcuts and along the edges of the timber. In the open high plains country the game is easier to spot, but it's surprising how much more game is seen looking through the right optics.

Several different high power binoculars are available today. Perhaps I should first define high power. I consider anything of 15 power or higher as being high powered. I have a pair of 10x50 binoculars that I use frequently, but when trying to judge antlers or tell which animal is the buck in poor light, they lack power if the distance is too great. I have found that a pair of 15x80 Steiner binoculars are excellent for general observation at long-range. Once an animal or varmint is spotted with these, I might go to something with more power but then again I might not. With the 10x50's I almost always go to something with more power after the animal has been spotted.

A drawback to using too much power for general observation is the limited field of view with higher powers. When I'm scanning an opening, I like to cover as much area as possible without missing anything. Some of the clearcuts in which we find deer, and occasionally elk, are up to 200 acres or so--a big area to look at.

The amount of light that is transmitted to the eye through a scope is dependent on its power, the size of the objective lens, and the quality of the lenses and coating. The overall quality of the binoculars depends on these elements as well as the care in their assembly and the quality of the optical design. There are two types of quality pertaining to any manufactured product, the quality of its design and the quality put into its manufacture.

Coatings for lenses were developed during the WWII period, although most of the optics used in that war were uncoated. An uncoated lens loses about 5 percent of the light passing through it at each lens surface. Early coatings cut this loss to less than half that amount. The multiple coatings of today, however, reduce the light loss to less than one half of one percent at each surface. Each manufacturer seems to have a proprietary lens coating that is, in their opinion, the best available. No doubt there are differences in coatings. I think though, that there is very little practical difference in the coatings used by the manufacturers of quality products. The emphasis here is on quality optics.

The size of the exit pupil, which is the diameter of the little circle of light seen in an eyepiece held at arm's length, determines how much light the eye receives. It is always expressed in millimeters and is found by dividing the size of the objective lens, in millimeters, by the instrument's power. For example the 10x50 binoculars I mentioned have an exit pupil of 5mm since 50 divided by 10 is 5. The 15x80 binoculars would have an exit pupil of 5.33mm.

I've also used a big set of Russian binoculars, 20 power with 110mm objectives. The exit pupil on these is 5.5mm.

Sally Lilja looking for spring black bear
Sally Lilja looking for spring black bear with the 20x110 Russian "Big Eyes".

Under normal daylight conditions, the pupil of the eye contracts to a diameter of about 2mm. When this happens, an exit pupil greater than 2mm in a pair of binoculars is not necessary, some of that light is not used. When the light is poor however, as it is in the early morning and evening hours, the pupil of the eye will dilate to about 5mm. Under dark nighttime conditions the pupil may dilate up to 7mm. During the poor light hours, when game animals are moving, are when that large exit pupil will demonstrate its worth.

When looking for a pair of binoculars then, the greater the diameter of the exit pupil, the better its performance will be in poor light conditions. As was mentioned, generally speaking the eye will not dilate beyond 5mm, so a pair of 7x35 or 10x50 or 15x75 binoculars will offer about all of the light your eye needs and can use. This same principle applies to rifle scopes.

If higher-powered binoculars are desired there are two choices. The expensive approach is to try and find a pair of the already mentioned WWII Japanese naval binoculars. The Japanese models are preferred because they had developed the lens coatings earlier than the United States and employed them in these binoculars. As a result they are superior for poor light use. A common power and size for these was 20x120--truly a pair of big binoculars, with an objective lens diameter of about 4.75".

Another approach is to assemble two spotting scopes together into a pair of binoculars. The 60mm Bushnell Spacemasters work very well for this and cost much less than original Japanese binoculars. The 22x wide angle eyepieces on the Spacemasters are a good way to go. They offer a wide field of view and a useable power with good definition. I have a single Spacemaster with this eyepiece and have used it when walking or riding my horse into an area, and weight is a consideration. That four legged beast comes in handy for packing out game too.

The 77mm Kowa spotting scopes also work very well for this application. I have used two of these in tandem and consider them to be as good or better than anything I have looked through. The large 77mm objectives mean a higher exit pupil value for a given power eyepiece. The set I used had the 25x long eye relief eye-pieces. I wear glasses, and this eyepiece allows me to keep my glasses on and still enjoy a full field of view.

The Kowa's really showed their value on a recent elk hunt. We were glassing some natural openings near the Montana/Idaho divide one evening. About 15-20 minutes before it was completely dark, we spotted some elk in a long narrow shoot about two miles away. With the 25x eyepieces, we could see antlers on a smaller bull. In the 10x50 binoculars you could see there were elk in the shoot but that was about all. With a pair of 7x35 binoculars the elk were barely visible. Had we not already known they were there, we would never have seen them with the 7x35s. I wish I could have compared the 15x80's but didn't have them along at the time.

A little later that same hunting season we were setup and glassing a semi-open hillside at daylight. Before long we spotted three elk about 1500 yards away. Looking through 10 and 15 power binoculars we couldn't be sure if any of them were bulls. I put the 25x Kowa's on the elk and could tell immediately, even in that pre-dawn light, that luck was with us. All three were bulls, one was a spike and the other two looked like raghorns or bigger. As it turned out at least one of the bigger boys was a five point, I tipped him over later that morning with a 300 Winchester Mag.

During the summer and early fall, there is a small bunch of whitetails that feed in an 80 acre hay field across the road from my house. With the Kowa's I can watch them in the evening until it is almost completely dark. They are usually 400-800 yards away. I'm looking to the east at them which helps in the fading light.

What is the upper limit in power? I believe that for general observation it is about 30x. As I mentioned earlier, as power goes up, the field of view goes down. Also, the mirage that target shooters are familiar with can become a problem when looking across a big canyon or the open prairie. Once something is spotted and a closer look is desired, 40x magnification is nice and about the limit in my experience, but not necessary. I'm not much of a variable power fan with spotting scopes. The eyepieces are expensive and often only used in the low to mid power range. With rifle scopes however, I like the big variable Night Force scopes. These scopes have a large 56mm objective, which makes them ideal for use in dim light situations.

Rangefinders

There are really only a couple of optical rangefinders that can be considered usable for long-range work. They are the Barr & Stroud manufactured model and the Wild. Baush & Lomb also made one during WWI but it is not as reliable or as easy to use. There are two basic models of the Barr & Strouds. The smaller version, referred to as the 250 model, begins reading ranges at 250 yards. It has a 31.5" baseline between objectives. The second model is the 500 yard model. As might be guessed, it starts reading distances at 500 yards. It has a longer baseline of one meter. Both models read out to 20,000 yards--farther than any shooter needs.

Barr & Stroud rangefinder
A Barr & Stroud rangefinder with a 1 meter baseline, 500 yard model.

As I recall, the Wild has a 70mm baseline. The optics in it are of high quality too, like the Barr & Stroud.

The 500 yard model B & S is actually more accurate than the 250 for use over 500 yards. The wider baseline allows it to be a bit more precise.

There are a few variations of these two basic models that I'm familiar with. There are some 250 yard models that are built on the one meter frame. I believe that these were all naval models. Also, there are some 250 models that actually read in meters instead of yards.

The Barr & Strouds are a very high quality optical instrument both physically and optically. They are of 14 power magnification. The image is of such quality that I have used the rangefinder at times as a spotting scope while shooting. In use, two images are seen in the right eyepiece. The upper image is upside-down; the lower, rightside-up. An object, such as a prominent rock or tree, is found in the image. A thumb wheel is then turned which will bring the two images into coincidence. When they are lined up, one on top of the other, the range to the object is read in the left eyepiece. Accuracy is quite remarkable--within about 5 yards at 1000 yards or so. They can be hand-held, but I've found that they are easier to use and more accurate if a tripod support is used. The same is true of the big binoculars.

With the naval models, both images are upright.

The Barr & Stroud rangefinders have not been made for many years. Their quality was such that if they had some amount of care, they are still very serviceable after 50 years or so. They are constructed primarily of brass and glass.

Since the militaries of the world have converted to laser rangefinders, no new optical rangefinders are likely to be made again unless a manufacturer feels there is a sufficient demand. The eye-safe laser rangefinder has been developed however. I've used the European models, the Bushnell, the North American Integrated Technologies model, and the Lieca 800 and 1200 models. All are good within limitations. The newer Leica models are very lightweight and dependable.

A Leica LAF 800 rangefinder. It operates on one 9 volt battery.

Rifle Scopes

Once the target has been found and ranged, it's time to launch a bullet at it. To be able to hit that target, a quality target scope is required. It must be of sufficient power so that the target is well defined in the scope image. The image must also be bright enough that the target is visible in poor light conditions. Perhaps the most important aspect of the scope is the reliability of its click adjustments. Long-range shooters don't hold over their target, they click the vertical adjustment of the scope up the correct amount and hold dead on. Knowing what the `correct' amount is, was covered earlier. Not all adjustments are what they are supposed to be or what the manufacturer states they are, though.

As an example of the importance of knowing what the click value is worth, I ran a drop chart for a friend recently for his 338-378 Weatherby Mag. He thought the clicks were .25 MOA and that is what I used for the input in the ballistics program. In checking his drop at 1325 yards, he found that he was hitting about 5 feet off the mark. The error was caused by his scope click value not being .25 MOA. It was about .282 MOA, and that difference meant quite a bit at this long distance.

I have used the Leupold target scopes for most of my own shooting and have been satisfied with their performance for the most part. A disadvantage with the standard target models is the limited amount of `up' adjustment they have. On my 338-378 rifle, I use a 24x Leupold scope with the scope bases milled on an angle, higher in the rear. This gives me more `up' adjustment but I'm still limited to about 1500 yards with this setup. With a 6.5x20 Leupold on another rifle, 1000 yards is the maximum amount of adjustment I can get. Both are good scopes, but they are lacking in adjustment capability for truly long-range shooting.

Another scope made by Leupold that does have more up adjustment than almost anyone needs is the current Mark 4 model. In the 16x version it has a total of 145 minutes of `up' adjustment. This is also the only scope I have used that has its click value calibrated for true MOA. That means that one click moves the image in front of the crosshair .262" at 100 yards, not one quarter inch (.250") or as is often the case, some other value close to one quarter inch but not quite. It has a unique focusing knob on the left side of the turret housing, opposite of the windage adjustment. This system is very easy to use, and it also eliminates parallax at the focused range. Some might consider 16x as being shy on magnification and I might agree with that for some types of shooting. Dick Thomas can do a power boosts on the 16x Mark 4. We'll discuss power in more detail a little later.

As I mentioned earlier, I've also been using the excellent Night force scopes. My favorite is the 5.5x 22 with the 56mm objective. I've been able to see .50 caliber bullets holes at 1000 yards with this model set at 22 power. That is exceptional performance for a rifle scope.

A Nightforce NXS 5.5-22 on a McBros 50 BMG rifle.

The big 2" Unertl scopes have long been favored by extended range shooters, and with good reason. The advantages include a large 2" diameter objective lens, comparable to the current crop of 50mm scopes. This size allows for an increase in the exit pupil for a given power, as compared to the more common 40mm objectives. Another advantage is the large range of vertical adjustment in the mount system, allowing the correct amount of adjustment for long-range shots. Also, when a good deal of `up' is dialed into the scope, the shooter is still looking through the optical center of the lens system. Not so with an internal design. The suspension-type mounting system also handles recoil well.

Unertl scope mounted on a barrel bedding block
A 2" Unertl scope mounted on a barrel bedding block.
The rifle is an improved 300 Weatherby with a Remington 700 action.

The Unertl scopes work best with either a barrel bedding block or a long receiver or sleeve. The idea is to keep the scope off the barrel. Because of the length of the Unertl scopes, the only alternative to conventional bedding and a short receiver is to put the front block on the barrel. It has been proven that this can cause unusual vibrations in the barrel and cause flyers. The Unertl scope in the photograph is mounted on the bedding block. The barrel is glued into the block and only the block is bedded into the Lee Six fiberglass stock. The action and barrel float.

Some long-range shooters have said they've had poor experiences with internally adjustable scopes because of recoil. They say that the best internal models available just won't handle the pounding that the big magnum cartridges produce. That hasn't been my experience, but I don't doubt that some have had the trouble they reported.

Thinking about this potential problem a little, I wondered just how the recoil of a heavy magnum long-range rifle would compare to a 6PPC 10.5 pound bench rest rifle. To find out, I ran some numbers through a computer program that calculates recoil. I think that most of us would agree that there are no problems with the internally adjustable scopes attributable to recoil on the 10.5 pound rifles.

There are three elements of recoil that add up to a given amount of `kick'. The first is recoil impulse, measured in pounds-second. The calculations for recoil impulse do not involve the weight of the rifle and it is more a measure of the cartridge, perhaps somewhat like measuring horsepower in a car. How the car will perform with that horsepower depends on its weight, gearing, wind resistance, etc. The second ingredient is free-recoil velocity. This is a measure of the speed at which the rifle comes back at the trigger puller, and is measured in feet per second. The third characteristic is free-recoil energy, which is measured in foot-pounds as is bullet energy.

In comparing the recoil of the two rifles, I used a typical 6PPC 10.5 pound rifle firing a 68 grain bullet at 3150 fps from a 27.5 grain charge. Recoil impulse was 1.4 lbs.-second. Free-recoil velocity was 4.4 fps, and free-recoil energy was 3.2 foot-pounds. Most of us are familiar with this amount of kick and wouldn't consider it excessive by any means.

For the heavy long-range rifle I used as an example a rifle of my own, which is pictured in this article with the Unertl scope on it. It is a tight neck 300 Weatherby that weighs 42 pounds. The load is a 220 grain bullet at 2900 fps from 76 grains of powder. With it I found that the free-recoil velocity is 4.2 lbs.-second. Free-recoil velocity is 3.2 fps (less than the 6PPC) and free-recoil energy is 6.7 foot-pounds (about twice that of the 6PPC).

After shooting both of these rifles one after the other, I find the 300 Weatherby no less uncomfortable to shoot than the 6PPC. I suspect that much of the reason for this is the low free-recoil velocity of the big thirty. I consider both rifles pleasant to shoot.

My point is, I sure can't see either from the actual felt recoil or from the computer's numbers that the recoil of the big gun is so punishing that it would tear up an internally adjustable scope. I also know that quite a few big gun shooters are using rifles that weigh considerably more than my 42 pound example. This would even further reduce the recoil. On the other hand, going to a bigger cartridge such as a 30-378 Weatherby or heavier bullets would increase it.

Eric Williams, the former editor of the Fifty Caliber Shooters Association's magazine VERY HIGH POWER, reports on another potential problem with scopes on muzzle braked rifles. According to Eric some of the brakes on today's fifties are so efficient that for a moment they are actually pulling the rifle forward. It is a very brief but forceful jolt and it seems as though it puts the scope into a kind of reverse recoil situation. Some of the target type scopes are not designed to take this forward thrust and soon develop loose parts inside. Eric did say that the Leupold Mark 4 seems to hold up, at least so far. It was Eric's fifty, with a Mark 4 on top, we used to shoot the tank hull at 2000 meters. This rifle had one of the type of brakes on it that can cause the forward thrust I mentioned. The scope seemed to be working just fine for me and it takes a lot of clicking to get on at 2000 meters.

The Night Force scopes have held up well to braked fifties too.

So far we have looked at some of the advantages and disadvantages of internally and externally adjustable scopes. Now we'll take a look at rifle scope power. Before using the 16x Leupold Mark 4 scope, I considered 20x to be about the minimum magnification for long-range work. I have used 24x scopes for the majority of my own shooting. An experience I had one hunting season caused me to alter my opinion on this a bit, though.

I was elk hunting in an area that had a few open parks, and the elk were using these openings in the early morning and evening hours. We had spotted a cow early in the morning, before the sun had risen over the mountain. A large antlered 6 point bull poked his way into the grassy area soon afterward. I picked him up in the pair of Kowas; he was a splendid bull. We quickly set up the portable bench and sand bags and positioned the rifle. I ranged the bull at 1010 yards through the Barr & Stroud rangefinder. I dialed the correct amount of adjustment into the 24x Leupold scope and found the elk in the small field of view. In the poor early morning light, I had trouble determining which elk was the bull in the scope. We were facing east which didn't help at all. To find out, I grabbed a pair of 10x50 binoculars that I'd laid down nearby, and with these I immediately could tell the bull from the cow. There was no wind blowing and I was very confident of a lethal hit. I knew my rifle and load well, so hitting a target at this range wouldn't be difficult. I was getting excited. Just as I reached for a 338-378 Weatherby round to place in the chamber, the big bull stepped into the trees. He never came back out.

exact spot where the bull appeared and then disappeared
This is the exact spot where the bull appeared and then disappeared.
The morning sun shows a glare in the photo much as it did in the rifle scope.

I wondered later, if I had been using a scope of lesser power and with a resulting larger exit pupil and brighter image, would I have seen which elk was the bull without going to the binoculars? If I had, I would probably have had plenty of time to fire a shot. The point is, less power may have been better in that situation. The exit pupil of the 24x scope is 1.67mm. A 16x Mark 4 has an exit pupil of 2.5mm, an increase of 50% over the 24x. A 2" Unertl scope in 24x would be about 2.1mm. In choosing a particular rifle and scope for just paper target work or small varmints, I would want at least 24x. On a rifle that may see some big game hunting however, less may be more.

It seems somewhat ironic to me that I do prefer the 16x to 24x power scopes for long-range work. On several of my 10.5 and 13.5 pound bench rest rifles I have scopes that have been bumped in power by Wally Siebert to 45x. These are used at just 100 and 200 yards. Why then, the lower power for long-range? I suspect that it is the increased field of view. It can be difficult to find a target at long distances with a limited field of view, especially if the target is uphill or downhill.

When clicking a scope knob up or down, it is very important to be able to keep track of where you are from a pre-established zero point. As I mentioned earlier, most shooters use a 100 yard zero as their reference point. The important factor, however, is being able to easily return to zero. In this regard, the Leupold adjustment knobs are superior to the Unertl system, in my opinion. The Leupold knobs have each minute of adjustment so indicated and they have a vertical mark for each click. One revolution is worth 15 minutes and each revolution up reveals a numbered horizontal line on the main body of the adjustment. With this system it is easy to keep track of your zero reference point.

The Unertl system on the other hand is difficult for me to keep track of. I almost have to count each click. The knob is numbered every two clicks, or half minute with conventional 7.2" spacing. This is not a big complaint, but my philosophy is that simple is better.

There is an alternative to clicking a scope up which some shooters have used successfully. That is to have a multiple dot reticle installed in the scope. The idea is to have a dot or cross wire placed a predetermined distance from another dot. The spacing might be, for example, 10 minutes apart. Another method is to have the dots placed for a certain range. I had Dick Thomas of Premier Reticules set up a 3.5-10 Leupold scope for me with 4 minute diameter dots at 300, 400, 500, 600, 700, and 800 yards. The cross wire is on the 300 yard dot. There is also a 3/4 minute dot above the cross wire for 100 yards. Using a system like this the shooter can also click between dots and gain some precision between dots or extra elevation beyond the last dot.

Earlier we mentioned shimming the rear base to gain `up' adjustment out of a scope. This principle applies to both internal and external models. Actually a better approach to this, with an internal scope, is to mill the scope bases on an angle. The rear base should be higher. If just the rear base is elevated, as it is when shimming, the scope rings are no longer in line with each other and should be lapped. If both bases are milled together, then the rings will be automatically in line.

Bruce Baer now manufactures a set of tapered bases for the Remington actions.

It is easy to calculate the correct amount to elevate the rear base. Let's say that a 24x internal scope has been installed on the rifle. After zeroing the scope at 100 yards we find that two complete revolutions (30 minutes) of adjustment have been `wasted'. We can gain back most of that adjustment by raising the rear of the scope. Thirty minutes of adjustment at 100 yards is about 30 inches. Now, we don't want to use all of that 30 inches in case we later change loads and find the impact has changed. We may need some of it later. Let's say that we want 20 inches of it back. So, how much do we want to change the bases?

First we need to know the spacing between the rings. In this example we will call it 6 inches. To find the correct amount to raise the rear ring we divide the 20 inches of elevation we want back by the number of inches in 100 yards (3600). This is then multiplied by the ring spacing in inches (6). This looks like (20/3600) x 6 = .033". The rear ring should be raised .033" for the correct adjustment. As mentioned, this same principle applies to Unertl mount systems if the maximum amount of `up' adjustment is desired. The Unertl scope in the pictures is mounted on a base which has the front mounting area surface ground .075" lower than the rear.

The long-range shooter has quite a few good choices when it comes to selecting top quality high power binoculars and spotting scopes. With the optical rangefinders, there is really only one suitable choice, the no longer manufactured Barr & Stroud models. Fortunately these are excellent instruments, very well designed and constructed. They can be difficult to find but are indispensable for true long-range shooting. Like scopes and binoculars, there is a fairly good selection of rifle scopes available for accurate long-range work. They will perform their job well if they are carefully chosen for the task and their limitations are recognized. Long-range shooting depends heavily on quality, no compromise optics.

Looking at What can go Wrong

We spotted the cow elk up high in a big semi-open alder patch of probably 20 acres or so in size. She was a long way out, just on the short side of a mile. We were hunting in northwestern Montana near the Idaho line. Soon another cow seemed to materialize in the brush. It had frosted several times early in the season and all of the leaves had dropped off the alders and brush. There was also snow on the ground so we could see into the brush fairly well with our binoculars and spotting scopes. Then behind the second cow came a 5 point bull, his yellow coat giving him away almost as well as his antlers did.

He worked his way down the mountain in our general direction and soon stopped to paw for grass in a small opening. I found him in the 14 power eyepiece of the already mentioned Barr & Stroud rangefinder and ranged him in at 1340 yards. I had my 338-378 Weatherby Mag rifle set up, and when I found him in the scope he was standing broadside. The angle indicator on my rangefinder read about 17 degrees. I had drop figures for 20 degrees and fudged just a bit for the lesser angle. I grabbed one of the big shells and chambered it. There was a slight mist falling from even higher up than the elk and it was coming straight down. I squeezed the trigger and both my spotter and I thought I hit him. The bull flinched a little and jerked his head to look downhill. I thought I had him.

338/378 Weatherby
Hunting elk early in the season in the Bitterroot Mountains.
The rifle is a 338/378 Weatherby.
Notice the Barr & Stroud rangefinder on the tripod.

This section will deal with causes for misses and poor grouping at extended ranges. As any experienced target shooter knows, it isn't always as easy as it looks. This is even more true with long-range shooting. There are some probable causes for shots not going where they were supposed to, though.

Some of the reasons for misses include rifle inaccuracy, incorrect range readings, wind drift, scope zeroing problems, and using the wrong velocity or ballistic coefficient or scope click value on the drop chart. Another possible cause comes from the effects of shooting uphill and downhill. We'll find out how changes in our rifle, load, scope, and drop calculations can cause a miss at long-range.

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