Sights are either iron sights or telescopic sights. Today we can buy very good telescopic sights for not a lot of money. The most popular seems to be the 3-9 power adjustable power.

For the beginner, a variable power telescopic sight with an adjustable objective (front) lens will work well for both offhand and bench rest shooting. Later on a higher power or more expensive scope may be needed for bench rest, but very good work can be done with an inexpensive telescopic sight.

Iron sights have risen in price and decreased in availability. Lyman still makes iron sights that fit many rifles, but the Lyman 48s and Redfield Olympics and Internationals are gone from the catalogs.

Write down all your sight settings. Even with the non-target adjustments on inexpensive telescopes, draw a picture of where the adjustments are for each range and load. Get one of those sticky-backed labels and put it on the stock of the rifle somewhere where it won't be touched a lot, such as the right side of the butt stock. Write down your sight settings for various ranges. If the iron sights don’t have arrows, make a sketch on the label showing which way the bullet goes with respect to sight movement. Adjusting the sights the wrong way is only funny the first dozen times you do it.

Considered in moderation, a bit of old advice about sights is just as good today as it ever was. It councils shooters to buy the best sights he can afford, and buy the rifle with whatever he has left over. The logic is that no gun can shoot better than it can be aimed, while even the cheapest rifle will shoot better than most shooters can shoot. A good scope will enable a cheap rifle to do its very best. A cheap scope that won’t hold zero or fogs up will actually prevent the finest rifle from doing even passably well. The older I get, the better council I find that advice to be. Ken Mollohan

Iron Sights

     Iron sights have (generally) no lens. (Some German Iron sights have provision for corrective lenses.)

Rear sights come in five broad styles:

“Open” rear sights have a “V” or “U” shaped notch, and are more suitable for hunting than target shooting.

Marble/Lyman tang sights come in various models, some adjustable for windage and elevation. These sights have a hole or “aperture” through which the front sight and target are viewed. These are also more suited to hunting than target shooting.

German Schuetzen rifle sights come in aperture rear and open rear styles. The aperture rear sight is mounted on the rear of the action-in the “tang” area. The open rear sight is mounted on a dovetail on the barrel. Both are adjustable for windage and elevation with a small wrench.

Vernier sights are most often associated with American made single shot rifles. These generally go on the tang of the rifle, have apertures to look through, are almost always adjustable for elevation and are frequently adjustable for windage. (Some rifles of the latter 1800’s era had vernier sights mounted on the heel of the butt stock for shooting from the “Creedmoor Position”. In this stance the shooter lies on their back with the muzzle resting over an ankle/crossed feet and the butt in their armpit.) True vernier sights have scales allowing recording of sight settings and return to those precise settings in the future.

Click-adjustable rear sights have apertures to look through, are adjustable for windage and elevation using knobs with “clicks” that can be felt and counted, and generally have scales used for recording sight settings. (These scales sometimes are verniers.) These would include Lyman, Redfield, Vaver and Anschutz sights. The apertures are interchangeable to adjust the hole diameter to light conditions and the individual eye.

Front sights come in four broad styles.

Bead front sights may have inserts of white or gold or red or other colors. These are more suited to hunting than target shooting.

Blade front sights are used by some target shooters, normally when shooting a military rifle match.

Globe front sights have been used for target shooting since the late 1800’s. They have a short tube with an arrangement for changing inserts. These inserts come in blade and aperture styles, and a myriad of others. Globe front sights with a set of inserts are required for precise target shooting from the bench, at least for folks over thirty with aging eyes. Globe front sights include the Lyman 17A and 77, Redfield Olympic, and others.

Windage adjustable globe front sights are typically used on American single shot rifles. The windage adjustment is required if the rear sight is not adjustable for windage; and many were not on the original rifles. Thus, many original single shots had elevation adjustment at the rear and windage adjustment at the front. I’ve always considered this a poor arrangement.

Some wind gauge globe front sights were/are made with a spirit level attached, so that the shooter could hold the rifle perfectly level and eliminate the horrid "cant"; a slight rotation of the rifle about the long axis. These sights are called "wind gauge globe spirit level front sights", with far more adjectives than any noun should be responsible for.

The spirit level is decorative, it hints at precision beyond its ability, and we love to say: "wind gauge globe spirit level front sight." Who cares if it works. 

Front sights adjustable for elevation are available from several sources. Sinclair sells a "Centra" sight, Brownells sells the "Schuster", and Medisha Firearms Ltd. sells a model with 65 minutes of elevation adjustment. When the elevation is in the rear sight, changing settings from short to long range means that the shooter's face must rise on and then over the stock. Variation in face-stock position is thought to make accurate shooting more difficult. I have found that shooting at long range with my face completely off the stock is uncomfortable.  With the elevation adjustment in the front sight, the shooter's face-stock position remains unchanged as elevation changes are made. An idea that makes perfect sense, although adjusting the front sight is more difficult than adjusting a rear or receiver sight.

You may also encounter some rather strange sighting arrangements at times. Almost anything you can conceive of has been tried at one time or another in the quest for accuracy and ease of aiming. Target rifles of muzzle loading persuasion are sometimes encountered that look as if they have a telescopic sight almost as long as the barrel. And yes, sometimes these really are telescopic sights. But more often, they are simple tubes that use the peep sight principle. They were sometimes preferred because they eliminated sighting errors that could occur from sun glare on exposed sights. The tube kept the sun off the front sight, which was mounted inside the tube, and more consistent accuracy was the result.

Some very early firearms used two identical sights, front and rear. Some oriental guns had what looked like a scope base at each end, with a ‘v’groove in each that the shooter lined up. Others had two posts - not unlike some modern shotguns. Many early guns had only a front bead. Many had no sights at all, and the shooter relied on ‘instinctive aiming’ and generally very short ranges.

     Also note that the term ‘iron’ sight is something of a misnomer: While most sights are indeed made of iron or steel, the term has come to be accepted as covering any sights that do not offer any optical augmentation of the shooter’s vision, regardless of the material used for its construction. I have seen crossbows with ‘iron’ sights made out of bamboo. Ken Mollohan

How to set click-adjustable rear sights

Most Lyman 48, 66 and 57 , Redfield and Parker-Hale PH 7A sights have one click equal to .002 inch, one click moves the rear sight .002 inch. If there were 1 yard = 36 inches between the front and rear sights, then moving the rear sight .002 inch would move the point of impact of the bullet one hundred times as far at 100 yards, or .2 inch. The Lyman 57 rear sight in the picture has an elevation scale marked in 3 minute divisions. One rotation of the knob has 12 clicks and moves the slide one division of 3 minutes.

The distance between sights determines how much one click of .002 inch moves the point of impact of the bullet.

Since 28" is the distance between sights on the Springfield 1903 rifle, and for some other fortuitous reasons, most click-adjustable American sights move the point of impact of the bullet about 1/4 inch per click at 100 yards when there is 28" between sights. Since one inch at 100 yards is almost exactly one minute of angle, one click moves the point of impact of the bullet about 1/4 minute of angle, abbreviated MOA. We say that these sights "have quarter minute clicks", but that is obviously only true when the distance between sights is 28". If, for example, the distance between sights is 36", then one click moves the point of impact .200 inch at 100 yards, .400 inch at 200 yards, 1 inch at 500 yards, and 2 inches at 1000 yards.

Lyman and Redfield elevation scales are graduated in minutes:

There are 12 clicks for a total of 3 minutes per complete revolution of the knob. The Lyman and Redfield knobs are marked "0, 1, 2", for minutes, with lines between the numbers.

The side scale is marked in 3-minute divisions; there are 3 minutes between each pair of marks.

Windage adjustment of the Lyman and Redfield sights is made in similar fashion, except that the scale is divided into left and right distances from center.

Here's an exception, a Lyman 48 sight on a M54 Winchester rifle made in 1928. This sight has HALF minute clicks, and the scale is marked in FIVE minute divisions. The rifle has 28" between sights. How do I figure that?

     The sight scale is marked from 0 to 150 minutes, and measures 1.2" from 0 to 150 minutes. A little dividing here (1.2/150 = .008) reveals that one minute is eight thousandths of an inch.

There are ten clicks per revolution of the elevation knob and one revolution is 5 minutes, so there are 2 clicks per minute, .004" per click.

There are 28 inches between sights on this rifle.

There are 3600 inches in 100 yards (12 inches times 3 feet times 100 = 3600). And 3600/28 = 128.57, so it's 128.57 times as far to 100 yards as it is between sights. So, any movement of the rear sight is magnified 128.57 times. Multiply 128.57 times .004 inches per click and we get .51 inches at the target. Close enough to half inch clicks for me.

Here's a BSA Martini with a Parker-Hale PH 7A sight. These sights have vernier scales. Inspection of the sight and review of the discussion on setting vernier sights below will enable you to set the PH 7A.

My Anschutz sight has no scales, I set it by counting clicks up from the bottom or side, or by experiment.

How to set vernier sights

The word “Vernier” has come to be used to describe the traditional tang sights fitted to single shot rifles; whether the sight has a vernier or not. Some shooters incorrectly associate the presence of an adjusting screw with the word “vernier”. A vernier scale allows setting sights very precisely, and the reading and recording of these settings. Vernier tang sights can be set to five-thousandths of an inch, (.005”). For instance, the sight may be set to .260” or to .265”-the precision of setting is .005”.

The left hand side of the drawing shows a vernier scale that might be found on a tang sight. The staff is marked “0”, “25”, “50”, “75”, “1” The staff divisions are spaced fifty-thousandths of an inch (.050”) apart. Then “25” is .250”, “50” is .500”, and “1” is 1 inchof elevation.

The slide is to the right of the staff, has one longer line on the bottom and four other lines.

The vernier is shown set at .250”, the bottom slide line lines up with the “25” line.

The drawings to the right are expanded, and show how the lines on the slide line up with the lines on the staff, allowing settings of .260”, .270” and so on. Only one line on the slide will line up with one line on the staff at any setting-this is the secret of the vernier. The bottom drawing shows the sight set at .305”, illustrating how the slide may be set “in-between” two lines. Note that the bottom long slide line is just above the .300” staff line, while the next highest slide line is just below the .350” staff line. This process of setting the sight allows precision of setting and recording settings to .005”.

How to adjust a wind-gauge front sight

The movable top part of my Maynard front sight (a representative example) has divisions 20/1000 of an inch (.020") apart. Every fifth division is longer, marking tenths of an inch (.1".) The bottom or stationary part of the sight has one line. There is no vernier on this or any other original front sight I have ever seen.

The distance between sights is 28”.

There are 3600 inches in 100 yards.

The ratio of the two distances is 3600/28 or about 129. A movement of the rifle sight is magnified 129 times at 100 yards.

So moving the front sight .020" or one division, with 28" between sights, moves the bullet 129 X .020" = 2.58". It is easy to set the sight between marks, for a 1.29" movement, and with a magnifying glass even smaller movements are possible.

     Looking into the muzzle of the gun, a movement of the sight to the right moves the bullet to the right on the target

How to adjust OTHER IRON Sights

Ken Mollohan

Screw adjustable iron sights are often encountered with no vernier or other indicator of what an adjustment is doing to your sight alignment. The usual expectation is to crank the screw a bit and shoot a couple of shots to see where you’ve arrived at. Then you do it again - and again - and again until you are ‘close enough’.

That’s really a pretty sad state of affairs, especially when it is so simple and easy to use that screw to make precise adjustments. Oh, you have to make some simple, one time calculations and measurements, but that’s all. The measurement only takes a few seconds at your local machine shop. Most machinists will be happy to use his thread pitch gauge to tell you the threads per inch of your adjustment screw. For purposes of illustration, I’ll assume you have a common, coarse 32 threads to the inch screw, but the same calculation works with any pitch.

Now one full turn of your screw will result in a movement of 1/32 inch, or 0.03125 inches. Measure the distance between your rear and your front sight. Again, for purposes of illustration, let’s say that it’s eighteen inches. These are the only measurements you will need to make.

Now let’s assume you are trying to sight in at 100 yards, because we want to get an answer in minutes of angle. A hundred yards is three hundred feet is 3600 inches. 3600 inches range divided by eighteen inches sight radius is 200. This (200) is the factor that multiplies the movement of your sight to give you the movement of the bullet impact at 100 yards. So if you move your adjustment screw one full turn, your bullet will move (0.03125 x 200=) 6.25 inches on the 100 yard target. Another way of saying this is that one full turn equals exactly 6.25 MOA. But for most purposes, it will be adequate to know that one turn equals about six inches at 100 yards. If you need greater precision, you can estimate eights of a turn and print a small table like this to tape on your stock, or keep in your shooting bag.

If this isn’t good enough for your needs, your machinist friend can undoubtedly make you a finer pitch replacement screw and run a matching tap into your sight base.

Some iron sights are even cruder, being adjustable for windage only with a hammer, and for elevation with a little set of steps in a groove to lift or lower the rear sight. It’s VERY seldom that one of these steps will coincide with your exact bullet impact and sight picture. The traditional response is to set it as closely as possible with such crude adjustments, and use ‘Kentucky Windage’, or hold off a bit to compensate for the error in your sights.

Well, at least something can be done for your elevation adjustments.  As before, measure the distance between your sights, and make a note of which step in your adjustment ladder comes closest to being right for your gun and ammo, without causing you to shoot too low. Measure the height of this step, and (using the techniques shown above) calculate how much you will have to shorten that step to be exactly correct on target.

If you are handy with tools, you can make this correction yourself with nothing but a file and a caliper or micrometer. But go slowly: It’s a lot easier to file off just a little bit more than it is to file a little bit back on! Or that machinist buddy can do it for you accurately, easily and inexpensively in just a few minutes.

Sad to say, there are also guns with absolutely NO provision for sight adjustments. Most of the older muzzle loaders fall into this category, as do a few very inexpensive modern rifles and many modern revolvers and pistols. When the point of impact is unacceptable, you have no recourse but to ‘get a bigger hammer’. For example, minor horizontal adjustments of revolvers can be made by rotating the barrel slightly. Horizontal impacts can also be made by enlarging the rear ‘sight’, which is little more than a groove in the top strap. Use Swiss files to widen the groove in the same direction that you want to bullet to go. Making the groove wider shifts the center of the groove in the same direction by HALF of the enlargement. You can calculate the correction needed (see above) or do it by file and try.

Vertical adjustments can be made most easily on the front sight: If your impact is low, you can file the front sight down, or replace it with a lower sight. If it’s high, you must elevate the front sight. If your gun doesn’t have a readily replaceable front sight, the most permanent solution is to weld or braze a small piece of steel on its top. Be sure it’s more than you will need, so that you can shape it properly as you file it down to bring your impact right on. I have also used epoxy to bond a bit of hardwood to the front sight in the same manner. This makes it easy to restore the gun to its original configuration with a little heat from a propane torch, and the wood takes black shoe polish quite well.

If you have any reservations about your ability to do work like this, your best option might be a machinist or gunsmith with a milling machine. Ken Mollohan

Telescopic sights

Telescopic sights may be categorized as "Outside Adjustable" and "Internally Adjustable."

Outside adjustable telescopic sights include Lyman Targetspot and Super Targetspot, Unertl, Litschert, Fecker and Davis brands. These have adjustments built into the mounts that are (mostly) click adjustable and clearly readable so that settings may be recorded. They have adjustments on the rear for focusing the crosshairs, and on the front (Fecker in the center) for eliminating parallax. It is entirely practical to move these sights from rifle to rifle, re-setting the sights each time.

These sights attach to "scope blocks" on the rifle barrel, which are most often 7.2 inches on center.

The adjusting knobs are marked in 25 divisions, and there is a click between each division, so there are 50 clicks per revolution of the knob. Each click moves the telescope one-half of one thousandth of an inch, .0005". Divide 3600 inches in 100 yards by 7.2 inches center distance between scope blocks and you get 500. Then multiply 500 by .0005" per click and you get .250" or a quarter inch or about a quarter minute of angle shift in bullet impact per click.

Sometimes scope blocks are mounted on centers other than 7.2 inches, and bullet movement at 100 yards varies as shown below:

Trouble with a Lyman Super Targetspot

I was working with an M54 Winchester in 30 WCF = 30/30 and a Lyman 30X Super Targetspot (STS) in the summer of 2005 when I ran into trouble. While groups were averaging about an inch and a quarter, every now and then a shot was missing. After taking advice and shooting at the center of a big target, I found that sometimes a shot showed up from three to ten inches low at 100 yards. These strangers were a puzzle.

    I cleaned the gun without finding anything unusual in the barrel.

    This is an old telescopic sight, most of the blue has been replaced by that much-desired "patina". I got after that patina with some 0000 steel wool and oil. Nothing looked any different when that was complete, the patina was still there. (Every time I shoot using a telescope, I wipe the scope down with an oily cloth.)

    Then I took the rear mount , the one with the adjustment knobs, off the scope and cleaned it. I took it apart, took the spring loaded 225 degree doodad off and apart, took the adjustment knobs off and the Chinese-character looking metal parts out. I cleaned and oiled the dickens out of the parts, and put it back together-not too hard. A toothbrush and some 3 in 1 oil and some clean rags did the job. There was quite a bit of stuff in there, dirt or old oil or ?

Back at the range many times since, many shots fired and not a stranger to be seen.

I think it was the scope, I think that some speck/s of stuff got in the workings and caused the very low shots.

Another problem with the Lyman Super Targetspot

I record the sight settings with information on the gun, load, distance and scope or iron sights, in my notebook. I have noticed that I have made many one-revolution mistakes when recording settings on a Lyman Super Targetspot.

Now I sort of understand why this happens and it's because of the design of the micrometer. I can only advise you to fiddle with the micrometer a while and get a good notion of what various settings look like and be careful when recording settings. It isn't you.

Internally adjustable telescopic sights include Redfield, Weaver, Leupold, Tasco and many other brands. The two features to look for, which make these sights most suitable for target shooting, are a front lens adjustable to remove parallax and graduated adjustment knobs from which sight settings may be recorded.

Some telescopic sights don't appear to be adjustable to eliminate parallax. There is no obvious adjustment available on the objective or front lens. Some of these may be adjusted to remove parallax. I have a Simmons 4X pistol scope that, with a little fiddling, can have the objective lens turned and adjusted to remove parallax. My guess is that all telescope sights have some means of adjustment to remove parallax during manufacture, and that this parallax adjustment may vary from easy to impossible for the shooter. In the end, parallax is eliminated by moving the front lens back and forth.

How to focus a telescopic sight

The conventional wisdom

The rear lens is adjusted to focus the crosshairs only. Aim the telescope at a cloudy sky or a neutral surface, glance through the scope, and adjust the rear lens until the crosshairs are clear and sharp. Do not look through the scope, glance through it for a second or so. If you stare through the scope then your eye will accommodate, and you won't do the job correctly. Do not focus your eye on anything except the crosshairs.

Parallax is the undesirable condition in which movement of the head while looking through the scope moves the crosshairs on the target. Parallax is more of a problem as the scope power goes up. Many scopes up to six power or so do not have an adjustment for parallax and work just fine for hunting or plinking. I have a M721 Remington with 6X Weaver without parallax adjustment, and it works fine, at least from fifty to 100 yards, for target shooting.

Most "external adjustment" scopes such as Lyman Targetspot and Super Targetspot, Unertl, Litschert, Davis and Fecker scopes have an adjustable objective (front) lens that is calibrated in yards, for easy setting. Many higher power and higher priced internal-adjustment scopes such as Weaver T36 and Redfield, Burris, Leupold and Tasco scopes have "AO" or adjustable objective lenses, to eliminate parallax.

My experience and opinion is that any scope without an adjustment for parallax hampers the ability of the gun to shoot targets accurately.

For target and precision shooting the scope must be adjusted to remove parallax whenever you move from one range (Ex 100 yards) to another (Ex 200 yards.)

Put the rifle or pistol on a rest, aim it at a target, and move your head around while looking at the crosshairs. If the crosshairs appear to move on the target, that's parallax. Adjust the objective lens until the parallax is gone.

The ranges indicated on the adjustment ring frequently don’t provide accurate adjustments for the range indicated. It is quite important to verify freedom from parallax by setting your rifle on sandbags and viewing your target from several different positions. If the crosshairs appear to move on the target, adjust the parallax until it remains immobile, no matter what angle it is viewed from.

(Fecker scopes were made with the parallax adjustment in the middle of the scope tube-for Feckers read "objective lens" as "middle adjustment.")

I figure that all scopes must have some means to adjust the front lens at the factory to eliminate parallax. I have taken apart some cheap scopes and failed to figure out how to do this. But, I was having parallax problems with a Simmons "prohunter" 4X32 scope on an M29 Smith & Wesson. There is a "?cover" thing on the objective lens that unscrews, under that is a doodad holding the lens. I was able to screw the doodad and objective lens in and out to eliminate parallax at 50 yards, and there is almost no parallax at 100 yards. So sometimes fiddling works. Sometimes.

"This can also be used to adapt ‘non-adjustable’ scopes for special purposes. For example, I need considerable precision for squirrel hunting, and need a scope for my old eyes. Most non-adjustable scopes are set to be parallax free at one hundred yards, but will exhibit more than enough parallax at 50 yards to cause me to miss a squirrels head. So I’ve modified several scopes for this purpose by threading the objective lens in and out until there was no movement at 30 yards, which is about the longest TYPICAL shot I encounter. Then I lock the setting in place with the cover screw, which is really a jam nut to keep the objective from un-screwing. The down side is that someday, someone might think the scope is worthless because his deer rifle wont group worth a darn with it, but I suspect it won’t be much of a concern to me then." Ken Mollohan

The unconventional wisdom

If and only if the above method doesn't make the image and crosshairs sharp and clear and in focus and parallax free, then it's time to break the rules.

For a long time I believed those who instructed me in the conventional wisdom, and only adjusted the rear lens to make the crosshairs clear and the front to remove parallax. I lived with out-of-focus scopes for years. Then I discovered that the conventional wisdom was wrong, at least sometimes.

Put the gun on a rest and aim it at a target. (If the front lens adjustment has markings, set the lens to the proper mark for the target distance, for instance 100 yards. If the front lens has no markings, just proceed.) Adjust the rear lens to bring the target, yes, the target, into focus. Adjust the front lens to eliminate parallax. Repeat this several times. When you are done the target and crosshairs will be in focus and there will be no parallax. Or close.

The conventional wisdom applies to scopes that have not been played with. If somebody has cranked the lens adjustments around, then the conventional method of adjusting the scope doesn't work. I unconventionally adjust several scopes a year for owners who tell me that I'm doing it wrong, but who are happy with the results.

Factors Of Sighting Error

Benchrest shooters have moved to 36 X telescopic sights and sometimes scopes with even higher power. We know (or think we know) that using high powered telescopic sights allows us to shoot smaller groups than when using iron sights. But, and there's almost always a but-there is some suggestion that iron sights can be used to shoot some very small groups.

At the Old Colony Sportsman's Association in Pembroke, MA, there is a Winter League Match shot every Sunday from November to March at 200 yards, offhand, at the military 200 yard target, from a heated shooting house. The black is 13", 10 ring is 7" and the X ring is 3". The categories are Iron Sights, Any Sights, Howes (10# rifle, 3# trigger, flat butt), Over 40 Caliber, Rimfire and Single Shot Rifle. The best target of each category is hung on the wall, so that at any time one may compare the best scores shot with, for example, Irons and Any Sights. By Christmas the scores are in the middle 190's. I have been surprised to see that the Iron Sights categories do not lag the Any Sight = Scope categories by much; sometimes not at all.

In the ASSRA matches, I believe that it was Dick Hughes that shot the first 250 at 200 yards with Iron Sights a few years ago. The 25 ring on the German Ring target is 1 3/4". Several other 250 scores have been shot since. I remember watching Jerry Ventura shoot the first record 250 with a scope on a Model 44 Stevens at Western New York/Alabama Hunt Club, maybe a dozen years ago. So the Irons aren't a great handicap.

And as a last example; I have found that I can shoot surprisingly small bench 100 yard groups with a good peep rear sight and an aperture-or even sometimes a leaf-front.

So-what effect do sights have on potential accuracy?

In The American Rifleman, April 1977, there is the article titled "Factors Of Sighting Error" by L.F. Moore that describes the results of testing conducted at Aberdeen Proving Ground with various sights and conditions. I've read this article many times since 1977, and consider the results very interesting and the article virtually incomprehensible. Since the work was done at Aberdeen, at Government expense, I feel no qualms about using the data from that article.

The test was designed to measure the dispersion about the center of the target with various sights.

The tests were done with the sights/rifles in a machine rest, a target at 100 yards that was moved with a synchro-torque transmitter-receiver system, an electrical spark system that marked the target paper on command, and several shooters. The target was moved out of alignment with the sights, the shooter looked through the sight and aligned the target with the sight using knobs for up-down and left-right and pressed a button that burned a small hole in the target. This was repeated for a series of "shots", the burned holes in the target forming a "group". This groups were measured and the Mean Radius (MR) was calculated and graphs were constructed using the MR data.

I interpolated the MR data from the graphs in the article. Since MR doesn’t mean much to me, the MR values were turned back into 5-shot 100 yard group sizes that I am familiar with. Jeroen Hogema of the Netherlands found, through some terrifying statistical analyses, that for 5-shot groups  group size = 2.5 X MR, so groups averaging 1" MR would have a group size of 2.5". Thanks again, Jeroen.

The information that I think is of particular interest is shown here in tabular form. The test identification numbers (Test # 7) are from the original article.

Notes on these tests:

• Test 2: "Effect Of Size Of Front Sight Aperture On Dispersion" Rear Sight .046" aperture

• Test 3: "Effect Of Diameter Of Rear Sight Aperture And Dispersion" Front sight .125" aperture.

• Test 5: "Effect Of Location Of Rear Sight And Dispersion".

• Rear sight aperture varied to suit, front sight .125" aperture

• Test 6: "Effect Of Location Of Front Sight On Dispersion" Rear sight .042" aperture, front sight 13 MOA aperture. Note that this test measures the effect of the distance between sights on dispersion. After 25", which with 2” from rear sight to eye leaves 23” between sights, the reduction in dispersion is minor.

• Test 7: Effectiveness Of Various Types Of Sights

• First Telescopic sights; then the M1, M14, M760 and M2 Carbine sights are aperture rear and post/bead front; the M94, M70, M99 and M760 are "open" sights, and the M12 had a shotgun bead front only.

The other tests:

• Test 1: "Effect Of Learning On Dispersion" showed that dispersion was reduced as the number of trials increased. But not much, from .312" group diameter at the first try, down to .15" group diameter after 40 tries.

• Test 4: "Effect of Target Type On Dispersion" showed dispersion varying from .15" group diameter on the NRA Smallbore Rifle Target to .375" group diameter on the "Game" target; with .042" aperture rear and .125" aperture front - 34" between sights.

• Test 8: "Effect Of Illumination On Dispersion" showed that in almost-darkness, with an M1 rifle, dispersion is large - about 1.5" group diameter; and with a 2.5 X telescope it is only .325" group diameter. Given some light, from about 2 candles/square foot to 30 candles per square foot, The M1 rifle dispersion is about .55"-.675" group diameter, and the 2.5 X telescope dispersion is pretty flat at .175" group diameter.

This test shows that we can't aim very well in the dark, that with a little light we can aim pretty well, and that we can aim more precisely with a telescope than with iron sights. Few surprises.

• Test 9: "Effect Of Target Type On Dispersion" First, with an M1 rifle, dispersion varied from .70" group diameter to .95" group diameter as target type varied from NRA Smallbore Rifle to "Game". Then, with an 8X Telescope, dispersion was .15" group diameter on the NRA Smallbore Rifle target, and .20" group diameter on the "Game" target. The author points out that "The smallest dispersion with match-type aperture front and rear sights was obtained with a round aiming point, approaching the small dispersion obtained on the same target with the 8X telescope, and actually surpassing the performance of the 2.5X telescope"

• Test 10: showed no difference in dispersion as sight finish was changed on an M1 rifle-normal finish or no finish on the sights, then sights blackened with a carbide lamp, and then with a red translucent front sight.

• Test 11: is hard to follow, but seems to show that tight fit between the stock and the shooter's face reduces dispersion.

• Test 12: "Effect Of Mirage On Dispersion" shows dispersion varying from .075" group diameter with a 20X Lyman STS telescope to .175" group diameter in heavy mirage with target iron sights.

There are several factors affecting accuracy, and the relationship between these factors is slightly complex. Let's say that there are rifle, ammunition and sight factors affecting accuracy. Then group size is the square root of the sum of the squares of the dispersion due to these factors, summed. For example: with a perfect rifle and ammunition the sights would cause a 2" group   with a perfect rifle and sights the ammunition would cause a 2" group with perfect sights and ammunition the rifle would cause a 2" group

     Expected group size = the square root of (2"X2" ammunition)+(2"X2" rifle)+(2"X2" sights)

     = the square root of (4+4+4) = 3.46"

     Now let the sights error fall to zero. Expected group size = the square root of (4+4)= 2.82"

This, at least for me, isn't intuitive or expected, but it seems to be true. I first read it in Harold Vaughn's book, and have encountered this relationship several other places since.

I got my copy of the original article from Rudi Prusok, ASSRA archivist. He can supply copies.

The work on MR and group size done by Jeroen Hogema is too frightening for this article. I will be happy to forward Jeroen's work by e-mail to those of you with too much time on your hands. I'm joeb33050@yahoo.com. joe b.