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Fitting & Zeroing Scopes

Fitting & Zeroing Scopes

ZEROING SIGHTS

This is how I've fitted and zeroed scopes for the past god knows how many years. It won't suit everyone, and is not intended to persuade experience shooters to use this method, but I find it is perfect for me. You need to be confident at single shot targetting.

I've just come back from a weekend shoot, but before leaving I had 6 guns to zero. 2 x S400's, 1 x R10. and 3 x springers. To be honest I struggled with the 2nd S400, (my mates). I made the mistake of assuming his scope had a MOA at 1/4". I eventually realised it was a target scope at 1/8" MOA. Happens to the best of us. No poblems at all with the springers. The R10 was zero correct after 3 shots. I use AA Field pellets for all zero testing and setting. The weekend shoot was spot on and we all enjoyed accurate targetting.

Fitting & zeroing Telescopic sights on an air rifle.

Part 1 Fixing Scope (I have not included the need for shimming)

First fit mounts to rifle rails and lightly tighten the bolts, just enough to hold them in place. Carefully place scope tube on top of mounts and observe the following :-

1) Springer Break Barrel, make sure when the gun is cocked that there is enough clearance between scope front lens, and the loading end of the barrel. You must be able to fit pellet in barrel without moving scope, and make a note of this position.

2) Springer Under Lever, when cocked, make sure that there is enough clearance between scope and pellet loading trough, and make sure pellet can be loaded without moving scope, and make a note of this position.

3) Co2 and PCP guns, make sure that pellets can be loaded in to trough, and for multi-shot check that both magazine and pellets can be fitted without moving the scope or mounts, and make a note of this position.

4) Finally, check rear of scope for eye relief. Carefully move scope back and for until you have a clear view through the scope. If you are seeing a part circle, (¾ moon) then keep repositioning scope until you can see a clear circle of view, and make a note of this position. This is the critical position, and where the scope must be positioned when finally clamping down.

Having completed this exercise, double check to make sure all positions can be accommodated, then remove the tube and tighten the mount bolts onto the rails.

This is a good time to adjust the eyepiece, or ocular focus. Look through scope, adjust the eyepiece so that the cross hairs inside your scope are focused. If they look fuzzy then rotate the eyepiece until you can see a clear cross hair. Once set, this focus need not be adjusted again. New scopes are normally set for 20/20 vision

The tube can now be fitted onto the mounts whilst observing all the required positions. The scope can now be bolted down, but, before tightening the bolts, make sure the cross hairs are both correctly set in the vertical and horizontal plains. You can now tighten all bolts holding down your scope, making sure that the eye relief critical position is observed.

At this point place gun to shoulder and look through sights, making sure you see a complete circle around your image. Repeat this exercise about 10 times until you are sure your eye relief position is correct. It is so important to get your eye relief position exact.

Before zeroing your scope we also need to consider Parallax Error. Parallax focus occurs when the point of impact (target image being viewed) does not fall precisely on the reticle plain. (Centre of eye ball).

Because a gap exists between the two focal plains, moving your eye off centre will result in a movement off the line of sight in relationship to the point of impact (target). Therefore it is considered that by keeping your eye central to the line of sight, the effect of Parallax Error will be minimised. It is also considered by many that the Parallax Error does not have so much bearing on scopes with less than 12x magnification. It is thereby considered that for air rifle applications, the eye relief line of sight is more important than the Parallax Error.

Zeroing your Scope is considered by many as an art, but it’s not. A simple calculation can make adjusting your scopes a real science, and not a difficult one at that.

Part 2 Zeroing Scope

What you need :- rifle, pellets, gun rest, table, measuring tape (50 yds preferred), A4 paper, target board, adhesive tape, Small ruler, pencil, note book.

Set up :-
1) place 36" of adhesive tape on floor, (Firing Line)
2) Measure 25 yds and place 36" of adh tape on floor (25yd target set line)
3) Measure 37.5 yds and place 36" of adh tape on floor (37.5 yd target set line, easier to calc)
4) Rifle support, this can be a gun rest, bean bags, even mother’s tights or father’s socks filled with sand. We need to allow sprinters to recoil, whilst keeping both Springer’s and PCP’s on target. We do not want a clamp, vice or Black and Decker’s Work Bench. !!!!!!!
5) Target with A4 paper. The A4 paper needs a dot in the centre with a vertical and horizontal line running through it.

Before zeroing the scope, we need to understand a few things about the scope and the turrets. First we have target scopes, then we have hunting scopes then sports scopes, but for zeroing purposes we will not differentiate. It’s the turrets we need to concentrate on. There is the horizontal scale and the vertical scale. These scales are shown on the side of the turrets on some models, and on the top of the turrets on others. When turning these turrets you will hear them clicking. Each click represents a measurement, known as MOA. (minutes of angle). Looking at the turret on your scope you will see something like : 1 Click = ¼"MOA at 100yards, or 1 click = 1/8" MOA at 100 yards, depending on the type of scope you use. The most widely used scale is 1 click =¼"MOA at 100 yards, which is the one we’ll use, and most likely the one you have.

All these figures are linear, and the incremental adjustment per click is proportional to distance covered. For example_:

¼" MOA at 100 yards means 1 click = ¼" movement on the target at 100 yards.
4 clicks to the inch.

At 50 yards 1 click = 1/8" movement on the target at 50 yards.
8 clicks to the inch.

At 25 yards 1 click =1/16" movement on the target at 25 yards (target set).
16 clicks to the inch.

At 12.5 yards 1 click = 1/32" movement on the target at 12.5 yards.
32 clicks to the inch

At 37.5 yards 1 click = 3/32" movement on the target at 37.5 yards (target set) (7/80" at 35 yds !!!)
10.667 rounded up to 12 clicks to the inch (makes for easier calculation.)

Lets Start

Set Target at 25 Yards

Place rifle (springer or PCP) on rifle rest, bean bag, mother’s stocking or whatever, (I use a wooden rifle rest which I built for less than £4 for PCP's, and a good bean bag for the springers), but make sure the gun is sitting firm, and aim directly at the centre of the A4 target using the scope. Squeeze trigger and fire at target.

Next, re-load and re-set the gun, aiming directly at the centre of the A4 target exactly as before. DO NOT FIRE.( I advise keeping safety catch on)

Take small ruler to target and measure distances of the pellet mark from both the vertical and horizontal lines. To simplify things, lets assume the pellet mark was 2" above the horizontal line, and 1" left of the vertical line.

At 25 yards 2" represents 32 clicks (16 clicks to the inch)

At 25 yards 1" represents 16 clicks ( 16 clicks to the inch)

Return to the gun and very carefully adjust turrets by the following. (The beauty of this method is that it doesn’t matter if gun moves).

Top turret, turn 32 clicks anti-clockwise to raise scope 2"

Right side turret turn 16 clicks clockwise to move scope left 1"

Now re-aim rifle at the target and fire gun with 2nd shot just to see where you are. Do nothing else. I often don’t bother with 2nd shot.

Now get target set at 37.5 yards

Re-load and place rifle (springer or PCP) on rifle rest, bean bag, mother’s stocking or whatever, aiming directly at the centre of the A4 target using the scope. Squeeze trigger and fire at target, exactly as before.

Next, re-load and re-set the gun, aiming directly at the centre of the A4 target exactly as before. DO NOT FIRE. ( I advise keeping safety catch on)

Take small ruler to target and measure distances of the pellet mark from both the vertical and horizontal lines. To simplify things, lets assume the pellet mark was 1/2" above the horizontal line, and 1/4" left of the vertical line.

At 37.5 yards ½" represents 6 clicks (12 clicks to the inch)

At 37.5 yards ¼" represents 3 clicks (12 clicks to the inch)

Return to the gun and very carefully adjust turrets by the following. (doesn’t matter if gun moves.)

Top turret turn 6 clicks anti-clockwise to raise scope ½"

Right side turret turn 3 clicks clockwise to move scope left ¼"

Your scope is now zeroed. Don’t believe me. Re-aim the rifle at the target, THEN FIRE THE GUN !!!!!

Because we rounded up the clicks from 10.66 to 12 a little bit of fine tuning can now be done on the range.

If turrets can be removed and reset, set them to zero on both scales. Some scopes allow this. (My scope won’t do this, turrets are fixed.

General comments

With regards to springers, some people are of the opinion that it is harder to zero a scope due to the recoil action, whereas in reality, the recoil is part of the gun's shooting cycle. Once you have mastered the recoil and can target shoot with reasonable accuracy, you should be able to zero in 4 shots.

The other observation I would comment on, is the need to group pellets together. I only use groupage to test my own shooting ability, and not the capability of the gun or the reliability of the pellets. Only when things go wrong, such as poor target accuracy do I then start to fire groupage shots to elimine the likely causes. They usually point to me!!!.

Hope you've enjoyed the read
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Cavatina
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