The Lahti Company
Arne Lahti
P.O. Box 453
Iron River, WI 54847
Phone: 715-372-5188
Toll Free 888-620-3366
Email: lahtico@cheqnet.net
URL: LahtiCompany.com
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(Extracted from "The Ultimate Sniper" by Major John Plaster, Paladin Press |
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A Cold Barrel Zero
Zeroing a rifle for the first shot from a cold barrel is desirable for some rifles that have a tendency to shoot a pattern that drifts from its zero as the barrel heats up. The first shot you will fire when you are hunting is from a cold barrel. If this shot is accurate it's the only shot needed. To determine if the rifle may need a cold barrel zero use THE 006 SPECIAL OPERATIONS REST to, hands off fire five or six shots at the same point on the target. If the impact point progressively moves away from the first shot you may need to zero for the cold barrel first shot.
One shot zero
It is possible to Zero a rifle scope with one shot, using THE 006 SPECIAL OPERATIONS REST.
Use a material like newspaper or a large piece of cardboard behind the target to create a large area for the projectile to hit. Align the scope to the center of the target and fire one round. If you can see the impact point remove the adjustment caps from the scope and use THE 006 SPECIAL OPERATIONS REST to focus the scope back to the center of the target. Now looking through the scope gingerly adjust the radical in the scope to the impact point by using the scope's windage and elevation adjustments. You are now zeroed with one shot.
A Grouping Zero
You have tested your rifle using THE 006 SPECIAL OPERATIONS REST at 100 yards, by the hands off firing of five or six shots at the same point on the target. You see the grouping is a one inch group. Now Zero the rifle to the center of the grouping. The impact point should now remain within one half an inch of the crosshairs at 100 yards. This is particularly significant for long range shooting. One inch at 100 yards is approximately one (MOA) minute of angle, 1 MOA = 1.047" at 100 yards. At 200 yards 1 MOA is approximately 2" and at 300 yards 3", 400 yards 4", 500 yards 5".... and at 1000 yard 1 MOA is 1O" approximately. As you can see your 1" grouping at 100 yards would be at least a 6" grouping at 600 yards. Now lets say your rifle tested out to be a 2" group at 100 yards. Your 2" group at 100 yards would be at least 8" at 400 yards and 20" at 1000 yards. If you know the trajectory of your projectile by heart and had any wind to contend with at all, common sense would tell you not to take a shot at a white tall deer with a kill zone of no more then eight inches past 350 yards.
Point blank zero and its maximum effective range
A Point Blank Zero would allow you to hold dead on the kill zone of your game, close up and as far away as its maximum effective range, which may be out to 300 or even 400 yards depending on the size of the kill zone of your game.
Use targets that approximate the size of the kill zone of the game to be hunted. For a white tail deer you could use paper plates (8" or 9") for the target. Use ammunition appropriate for the game to be hunted. Put a target at 50 yards out. Use THE 006 SPECIAL OPERATIONS REST to zero the rifle to impact the top of the target about 1-1/2 inch in at 12 o'clock as you point dead center at the target. Now put out targets at 100, 150, 200, 250, 300 yards and so on. Use THE 006 SPECIAL OPERATIONS REST and shoot each of the targets from 100 yards and out pointing dead center of the target. You will see the impact point move down from the top to the bottom of the target as you go out in yards. When you shoot the target that the impact point is 1-1/2" from the bottom of the target you are at the maximum effective point blank range for the rifle and round being used. Zeroing a rifle for a point blank zero, eliminates the need for range estimation except for the maximum effective range at which pass this point you would not shoot. The maximum range may surprise you as being a considerable distance. Now remove the rifle from the THE 006 SPECIAL OPERATIONS REST and shoot the targets to determine your maximum effective point blank range.
Matching The Round And The Rifle To Work In Harmony
Each rifle has its own specific character based on it fiscal makeup and so does the round being used. If the two do not sing in harmony you will have a rather unpleasant looking test grouping, too wide for excepted accuracy. There is more than one way to get the two in harmony using THE 006 SPECIAL OPERATIONS REST. For factory ammunition choose the appropriate type for the game or target. Then buy different brand names of that type of ammo and test each one's grouping with the rifle. Zero the rifle for the brand name ammo that groups the best in that rifle. Then buy up as match of that brand name in the same lot number as you can afford. When you use that lot number up, redo the process and re-zero the rifle. Another way to match the two is to tune the rifle to the ammo with a harmonic tuner that installs on the end of the barrel of the rifle. This tuner you can turn in and out to match the rifle to the ammo used. If you reload ammo you would work up the powder charge to match the rifle. And if all else fails, have a gunsmith free float the barrel and glass or steel bead the action of the rifle then test.
Parallax
Parallax is an apparent change in the direction of an object by a change in the viewers position. Careful attention must be paid to this phenomena in order to obtain an accurate zero with a scope. To see the affects of parallax, place a scoped rifle in THE 006 SPECIAL OPERATIONS REST and put a target that has minute of angle line on it 100 yards out. Look through the scope without touching the rifle and move your head forward and back and side to side. You will see a shadow inside the scope that will move as you do. You will also see the crosshairs move on the target without you moving the rifle. This is parallax and an inconsistent position of the eye to the scope that produces an inconsistent impact point on the target. To eliminate this problem move your head back to the point you see the shadow around the side of the scope. Now move your head forward so the shadow disappears equally centered to the sides. This will minimize the parallax and produce an accurate zero.
Scope Adjustments
A point of confusion with scope adjustments, is that when you do a one shot zero and you turn the elevation adjustment in the direction marked up, you see the focal point move down to the impact point. The same goes for the right and left adjustments, you see the focal point move left when you turn it in the direction marked right. To keep this positioned in your mind, which way do you turn the adjustment if the impact point is one inch low at 100 yards, if the impact point needs to move up to the focal point? You would turn in the direction marked up. The same goes if you are one inch left of the bulls eye, you need to turn the windage in the direction marked right to move the impact point right. Now how much do you turn it? This depends on the (MOA) minute of angle of one positive click for the scope adjustment. One MOA is 1.047" at 100 yards or approximately one inch at 100 yards. To determine the MOA for one click of the adjustment on the scope, use a target with one inch grid lines on it and put it at I 00 yards. Use THE 006 SPECIAL OPERATIONS REST to hold the rifle on the target. Remove the scope caps. Now use the scope to view the target as you turn the scope adjustment back and forth one click. If you see the crosshairs move 1/2" back and forth on the target the scope is a 1/2 MOA, if it moves 1/4" it is a 1/4 MOA scope and you see 1/8" you have a 1/8 MOA scope. For example, you have determined the scope is a 1/4 MOA and you are 1" low and 1/2" right at 100 yards, you would move up four clicks and move left two clicks to zero it.
Some scopes have a (BDC) bullet drop compensator. A very handy use for THE 006 SPECIAL OPERATIONS REST is to determine the COME UPs for each bullet weight you will use in the rifle. (see COME UPs).
COME UPs and MOA
Different weights will have different trajectories so you need to determine the come ups for each type of round you will use. A COME UP is the number of clicks to come up from 100 yards to be dead on at 200 yards, the number of clicks from 200 yards to 300 yards and the number from 300 yards to 400 yards and so on until you run out of clicks on the scope. This pattern of numbers is unique for the velocity and weight of the round being used, because of the affect velocity and bullet weight has on trajectory. You memorize the pattern of numbers for the round being used. Let's say you are hunting and range your target at 400 yards out. You know the COME UP from 100 yards to 200 yards is 9 clicks and you click that up, 200 to 300 yards is 12 clicks, 300 to 400 yards 14 clicks, you hold dead on and bulls eye.
To determine the COME UPS use THE 006 SPECIAL OPERATIONS REST to shoot targets set out in 100 yard intervals. To determine the clicks you need to have an understanding of MOA. If your scope is a 1/4 MOA, one click is 1/4" at 100 yards and one click is 1/2" at 200 yards, 3/4" at 300 yards and at 400 yards one click = 1" on the target. For example, if you are 4 and 1/2 inches low at 200 yards and 1/4 MOA = 1/2" at 200 yards you would click up 9 clicks because there is 9 (1/2's in 4 and 1/2"). Another way to look at it is, 1 MOA is 1" at 100 yards, 2" at 200 yards and 3" at 300 yards and so on. 4 and 1/2" low at 200 yards is 2 and 1/4 MOAs low. So you come up 9 clicks for a 1/4 MOA scope and you write down that number as the 100 to 200 yards COME UP. Now shoot 200 yards to verify and go on to the 300 yard target.
The impact point is 9" low at 300 yards. OK your 1/4 MOA scope equals 3/4" at 300 yards on the target per click so 9" divided by 3/4" (.75") = 12 clicks or you could say (9" at 300 yards = 3 MOAs) because 1 MOA=3" at 300 yards. So 9"/3" = 3 MOAs and you click 12 up with a 1/4 MOA scope to equal 3 MOAs. Now write that number for the COME UP from 200 to 300 yards and shoot the 300 yard target to verify and move on to 400 yards.
It is 14" low at 400 yards, this is to simple, if 1/4 MOA = 1" on the target at 400 yards, it is 14 clicks up. You COME UP 14 clicks and shoot to verify and move on until you run out of clicks on the scope. For example you will have a set of numbers like 9, 12, 14, 16, 18, 20, 23, 26, and 29 for that round as COME UPs.
MOA Equivalents & Distance in Yards
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100 |
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400 |
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800 |
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1000 |
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| 1 MOA= |
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1" |
2" |
3" |
4" |
5" |
6" |
7" |
8" |
9" |
10" |
| 1/2 MOA= |
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1/2" |
1" |
1-1/2" |
2" |
2-1/2" |
3" |
3-1/2" |
4" |
4-1/2" |
5" |
| 1/4 MOA= |
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1/4" |
1/2" |
3/4" |
1" |
1-1/4" |
1-1\2" |
1-3/4" |
2" |
2-1/4" |
2-1/2" |
| 1/8 MOA= |
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1/8" |
1/4" |
3/8" |
1/2" |
5/8" |
3/4" |
7/8" |
1" |
1-1/8" |
1-1/4" |
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