How to: Level your riflescope

Close up of scope turrets

Chris Parkin explains how to correctly level your riflescoe - Credit: Archant

Chris Parkin looks at the procedure for correctly levelling a riflescope and explains why it’s so important for accurate shooting

View down a riflescope

(1) - Credit: Archant

Holding your rifle vertically (1) without ‘cant’ is a critical aspect of any type of shooting and becomes more important as ranges increase. Various accessories exist to help with this, including scope mounts with internal bubbles (2) and additional bubbles that clamp onto the scope tube (3), Picatinny rail or rings. There are also electronic options integrated into some day/night vision digital riflescopes, but although these can offer consistency they don’t guarantee accuracy when setting up a riflescope in its mounts.

Scope mounts with spirit level

(2)

Reticles are often judged to be visually level at setup, with the lower 6 o’clock stadia effectively aligning with the bore axis (4) – although some shooters prefer some ‘lean’ in this situation... but we then enter a bit of a rabbit hole as to which is the correct way to progress.

That reticle is etched (5) on a circular lens clamped and bonded within a circular tube suspended within the mechanical adjusters for windage and elevation inside your scope. This erector tube is what moves up, down, left and right to set initial zero and if dialling is your preference.

Levelling bubble clamp on side of riflescope

(3) - Credit: Archant

Two factors now appear. The first is that with perfect alignment between reticle lens and tube, the tube itself should transit up and down without any lateral shift affecting windage. The second factor to consider is that if the reticle is rotationally misaligned within that tube and you choose to aim off laterally or vertically using reticle systems with additional mil-dots or hash marks (1), you may not be truly applying offset in a single axis.

[Please use - pic listed in the copy - no caption]

(4) - Credit: Archant

Everything that’s manufactured is done to a price and tolerances – it’s just a fact of life. So in general the more you pay, the more precision you should expect. Getting the scope set up in the rings is a primary starting point for which some manufacturers offer proprietary solutions such as alignment wedges (2) for the scope mount to effectively ensure that the underside of the scope’s saddle is parallel to the surface of the scope mount or the Picatinny rail itself.

The second method is additional accessories that attach to one or multiple surfaces to help with what we can term mechanical alignment (6) of the scope’s internal mechanisms to the bore. In other words, does your elevation turret point directly up?

Scope reticle etching process shown on a poster

(5) - Credit: Archant

Most Read

Lastly, there are more improvised systems where individual low-cost bubble levels can be bought for pennies (7) and applied to many hopefully intentionally parallel surfaces of the rifle, scope turret (make sure you are on a flat surface) and accessories. This is about as much as we can do; the proof/refinement of the process is when you test fire the gun! (7) shows a deliberately misaligned scope with all the bubbles level! The corresponding reticle is seen in (8).

I covered the details of what’s called a tall-target test a few months ago, in which you shoot a group at the base of a tall, perfectly vertical line at point of aim before dialling in significant elevation to see if the upper group still intersects that line, using the centre point of the reticle alone as your aiming solution.

Mechanical alignment of scope on rifle

(6) - Credit: Archant

With all other factors disregarded and the reticle itself held parallel to the line on the target (to ensure zero canting), if the subsequent hole on the target shows lateral movement, your scope is not moving truly vertically and this must be attended to. It’s a matter of trial and error, marking the scope tube against a known reference on the rifle and lower ring (not the adjustable upper ring top) fixed to the gun. Small incremental rotational steps and retesting will show the truth.

This is simple (if time consuming) with a basic centre aimpoint, but if you are using a complex reticle with multiple holdover points on vertical and lateral arms you must test if that reticle is rotationally correct within the tube, i.e. is the mechanical movement within the scope’s elevation and windage turrets aligned to all the dots and hash marks? Now you must effectively do the same tests, with all other variables removed, to see if your aim-offs, vertically and laterally, move the point of impact truly vertical or lateral, with no secondary effect on the other axis. If you aim 6 mils high, is your group still central?

Low cost spirit level bubble shown on a riflescope

(7) - Credit: Archant

Bear in mind that in scopes at the lower end of the market, reticles and mechanics aren’t always perfectly aligned and errors are not uncommon. But at the high end, for long-range shooters or anyone relying on exact ballistic corrections, all must be perfect, so it’s not unknown for a scope to go back to the factory under warranty to have a reticle reset.

These tests must be performed under calm conditions and with careful thought about what you are compensating for and truly expecting. This is not an exercise in shooting technique or precision, but can offer interesting results and also help you assure yourself that as well as having correct alignment, you are maintaining a sure aim point and are able to accurately dial or aim off corrections.

An off centre reticle shown through a riflescope view

(8) - Credit: Archant

Coupled with techniques like box testing, this will assure you of the performance of your scope and rifle combination long before you bring in variables like wind, environment, spin drift, etc, into play. I review rifles, I don’t test them, and there is a big difference.

A review is based on my opinion of factors presented, whereas a test is more scientific and can be peer reviewed, with others recreating identical scenarios to see if they achieve the same results. Although tools will help with scope setup, they do not completely negate the need to test the results with uncontrolled variables ruled out or at least identified and minimised. Please write in if you would like to see this topic covered in more detail.