How to level a scope

by Tom Gaylord, a.k.a. B.B. Pelletier

This report covers:

• Why does a scope need to be leveled?
• Scopes cannot be leveled.
• A leveling solution.
• Bubble levels.
• What works
• What about a collimator?
• My moment of enlightenment.

I promised this report to blog reader Genghis Jan over half a year ago. Several times, I’ve started to write it and turned away, but today I’m seeing it through.

Why level a scope?
There are 2 reasons for leveling your scope. The first is psychological. If the reticle inside the scope appears to be slanted to one side when you mount it on your gun — and I am primarily talking about rifles today, although these principals apply to scoped pistols just as well — it’s disconcerting. The second reason for leveling a scope is to ensure the vertical adjustments move the strike of the rounds vertically, and the horizontal adjustment do the same. If the scope does not appear level, the adjustments will move the rounds off to one side or the other as they move up and down.

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FWB 300S vintage target air rifle: Part 5

by B.B. Pelletier

Part 1
Part 2
Part 3
Part 4


The FWB 300S is considered the gold standard of vintage target air rifles.

This is a test I said I would do the next time I got a calm wind day at the range. That day came last Friday, and I took the opportunity to test the FWB 300S at 50 yards with a scope. This test was designed to see if there is any discernible accuracy difference between pellets that are sorted by weight and those selected at random from the tin. If you read part 4, you’ll see that I was surprised to find that these JSB Exact RS pellets I selected for their accuracy had such a variation in weight. I sorted through almost 40 pellets to find 20 that weighed exactly 7.3 grains. Though the weight difference was only four tenths of a grain, it was more than expected and more pellets were affected than I thought.

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Pellet velocity versus accuracy test: Part 7

by B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6

Before we begin today’s report, I want to reflect on a truth that helps explain why we’re sometimes dissatisfied with things when we get them. I was at the range last week testing some airguns, and I was using my Celestron 70C spotting scope, like I always do. This scope is good at 50 yards, but becomes marginal at 100 because it cannot resolve the smaller bullet holes. I don’t mean pellet holes, I mean .22-caliber bullet holes in the black bullseye at 100 yards.

A friend brought his Burris spotting scope to the range for me to compare, and the difference between the two was night and day. His scope was sharp enough to see small spiders walking on the target paper at 100 yards!

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Pellet velocity versus accuracy test: Part 6

by B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5

For the benefit of readers who have landed on this article first, this is the sixth test in a series of reports designed to test how velocity affects accuracy. I’m using a Whiscombe JW75 breakbarrel/underlever rifle with a .177-caliber barrel installed. That way the same powerplant is being used for each test. I’m controlling the power of the gun by the use of different air transfer port limiter screws that allow less and less air to past through.

The Whiscombe rifle uses dual opposed pistons that come together to compress the air when the gun is fired. The rifle has no recoil and just a minor impulse that can be felt — yet it’s one of the most powerful spring-piston air rifles ever made. My rifle can produce over 30 foot-pounds in .25 caliber.

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Pellet velocity versus accuracy test: Part 5

by B.B. Pelletier

Part 1
Part 2
Part 3
Part 4

Today we look at the groups made by the four pellets used in this test at 25 yards when the velocity is diminished. Part 4 covered the velocity for each pellet, so go there to see where each one is.

If you like nice linear results, prepare to be disappointed. Today’s target do show changes, but they may not be in the direction you expect. Let’s get right to it.

First up were the 7.1-grain Beeman Devastator pellets. These pellets have been a real surprise in this test, because they have proven to be accurate at supersonic velocity and they are not sensitive to bore conditioning. Shoot one and it tends to go to the same place every time. They also do not show any first-shot tendencies that so many other pellets do. This is a real plus for hunters, who are always shooting the first shot. I will have to return to this pellet sometime soon and test it in other guns, because it seems to be a real winner.

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Pellet velocity versus accuracy test: Part 4

by B.B. Pelletier

Part 1
Part 2
Part 3

Today we lower the velocity of the Whiscombe and test each of the four pellets, in preparation for the next accuracy test.

One reason I selected the Whiscombe for this series of tests is the fact that I can control the power output over a wide range of velocities by installing various transfer port limiters. For those who are new to airgunning, every spring-piston airgun like the Whiscombe generates a brief blast of compressed air by means of a piston racing forward in a compression tube. In the Whiscombe’s case it is actually two pistons racing towards each other. At the exact end of their travel a small air tunnel called an air transfer port conducts the compressed air from the compression chamber to the base of the pellet, where it blows it out the bore.

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Why do you need a scope level?

by B.B. Pelletier

I’m writing this report because I saw from the comments on the accuracy versus velocity test that several readers do not know what a scope level does. And where three people speak out, there are three hundred who are reading and remaining silent.

They say that there’s nothing more zealous than a convert, and I expect that is true of me when it comes to scope levels. I have understood their need for a long time and even conducted a fairly extensive cant test back in my Airgun Letter days, but it was my .38-55 Ballard single-shot rifle that really drove the message home. That rifle came with a bubble level, and it’s far more precise than the levels we find on air rifles today. The bubble moves very slowly, making it important to check the level just before you begin the squeeze; because what looks like a level gun one moment can change slowly to a canted gun if you don’t watch the level. By contrast, the scope levels I’m using with airguns have bubbles that move very fast, are much easier to see and are far simpler to work with.

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