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  • Post last modified:August 14, 2023

In this informational guide, we gonna break down 0 vs 20 MOA base mount for precision rifles.

You will learn what they're and when they're appropriate to use.

One of the many choices a long-range shooter must make when setting up their rifle and scope configuration, whether to go with 0 or 20 MOA base.

In this article, we will examine the advantages of both systems and their applications for long-range shooting.

  • What is a 20 MOA Base and Rail?
  • Distances for this setup
  • MOA elevation travel
  • 1000 yards and a 20 MOA Base
  • ZERO

0 & 20 MOA Explained

20 MOA scope ring cant

The impressive thing about the modern era of target shooting and hunting, there are so many fascinating options and modifications to be made to our equipment.

Long-distance targeting no longer revolves around 200 or 300 yards; the emphasis is 600 and 900 yards. Understanding MOA and how this measurement applies to scope mounts and rails is critical to precision.

As a general rule of thumb, keep the MOA of your base less than ½ of the elevation adjustment range of your scope. Any more than ½ and it is unlikely you will be able to zero at close range.

Minute of angle

What is MOA? In practical targeting terms, MOA alludes to the tilt of a scope base relative to the bore axis. 0 MOA has been the standard targeting arrangement for decades. 0 MOA is a flat configuration, as depicted.

If the rifle was zeroed at 100 yards, a line-of-sight laser.

from the bore axis and center of the scope would converge at the target. What this implies, a flat or 0 MOA base will use only about half of the total scope adjustment range.

For most standard cartridges, a 0 MOA base has a soft limitation at around 600 yards.

sphur 20 moa ISMS scope mount
Referenced RECOIL

A 20 MOA base and the scope's line of sight strikes the target. However, the line of sight for the barrel will hit twenty inches high. Dial the scope back, so it hits the target.

What this means for the shooter, they have an extra 20 inches of elevation adjustment to play with.

Related Content: How To Adjust MOA With Precise Calculation

What Does A 20 MOA Scope Base Do?

0 vs 20 moa scope base

A scope with 40 MOA has roughly 20 MOA of unusable adjustment; the same holds true for any amount of MOA.

In most instances, standard scopes run out of elevation adjustment range at about 600 yards.

In other words, when a rifle has been centered at the scopes travel, there is 20 MOA that will never be used. A 20 MOA base gets back the elevation that is wasted.

At first sight-in, the idea of a 20 MOA base feels strange to the shooter. It feels comfortable with the scope pointed up rather than down.

scope elevation adjustment and rail cant
Referenced PRB

A 20 MOA base is canted down to the front of the rifle barrel, and this allows for more usable elevation.

Take another glance at the illustration above. The rifle barrels line of sight is hitting the mark at the center while the scope's line of sight is 20 inches high of the center.

This is the theory of how a 20 MOA scope base works. If you are zeroing at 100 yards, you have an extra 20 inches of elevation to work with.

At What Range Is A 20 MOA Scope Base Needed?

expert long range shooting tip
Referenced Ballistic Magazine

The answer to the above question entirely depends on the shooter, rifle, scope, and the cartridge. Long-range targeting is now at 600 yards and above, and in most instances, 1000 yards is the distance to shoot for.

A 20 MOA base is not necessarily the only option when shooting extreme distances.

As an example, when a BDS (ballistic compensating reticle) is used, a 20 MOA base may not be needed. The reason, a shooter is not using elevation to hit the target; here, a 20 MOA serves no purpose.

With some scopes, being paired with a flat shooting cartridge, the added 20 MOA of elevation can not be used to zero the gun at 100 yards.

If you stand firm on buying a 20 MOA base, the rifle must be zeroed at 200 or 300 yards. For some shooters, this would be unacceptable.

It is essential to know how much MOA elevation travel a scope has before making a purchase.

MOA Elevation Travel


When a shooter turns the elevation turret on their scope, a corresponding erector assembly is being adjusted up or down inside the tube.

The reticle floats inside the erector assembly. If the scope has an internal rating of 60 or 100 MOA, the movement of the erector assembly is the total top-to-bottom MOA.

Assuming the rifle and scope are level, elevation adjustments should be in the middle of its total travel when zeroed at 100 yards. As an example, a scope with 60 MOA will have a zero at 30 MOA up from the bottom.

This limit in elevation adjustment limits the maximum engagement range. A 20 MOA base gets around this internal limit. A canted scope base with 20 MOA of elevation adjustment shifts the zero from the top.


Check out this cool gadget from COLD SHOT LLC for long range shooting and ELR applications.

It features a 300 elevation adjustable scope base system, and it was designed to eliminate the problems associated with distortion caused by “bending” light through as many as (10) lenses within modern scopes.

Learn more here

MOAB COLD shot scope base
Features MOAB Gen 4 Base Mount

Do I need a 20 MOA rail to shoot 1000 yards?

Short to medium distances, a shooter does not need a tapered base, for most scopes there is plenty of internal elevation adjustment. At 1000 yards, a flat rail does not have enough elevation to match the point of aim with the point of impact.

A shooter should have their scope optically centered, relative to turret travel, before leaving the store. Optically centered ensures you get half the total MOA in either direction.

Assuming you have a scope with 70 MOA elevation travel. A flat base leaves you somewhere in the neighborhood of 33 MOA elevation up from a 100 yard zero.

This is where a lot of the above conjecture depends on ballistics, specifically the load. Let's assume you have a 308 leaving the barrel at 2650 fps. You should be able to reach 1000 yards with optimal conditions. (1000 feet of elevation, 50% humidity, and a balmy 75 degrees)

Optical quality heads south at extreme distances. Based on the above assumptions, you are better off with a 20 MOA if the load requires over 30 MOA to reach 1000 yards.

Related Content: Best Long Range Precision Scopes Under $1000

20 MOA Base and Zero

20 MOA scope base

Most shooters are familiar with targeting in the 200 to the 300-yard range and zeroing their rifles at 100 yards. However, with modern ballistics, high powered scopes, and rifles, marksman want the thrill of that long-range shot. Whether this thrill equates to hunting is a whole other story.

50 Yard Laser Bore Sight

The quickest way to zero a rifle with a 20 MOA base is to use a laser bore sight first. This step gets you on paper.

Even without a laser, shooters can look through the barrel at a 50-yard target, then adjust the reticle to be at center. This will get you close, and you can make elevation adjustments from there.

100 Yard Zero

shooting range NC
Features Frontline Defense Range, NC

A 20 MOA rail changes the interaction between a scope's line of sight and the line of sight for the bore. The angle is widened between the two. However, the line of sight for the scope and bore remains a constant when the aiming point is specified at 100 yards.

On our site you can check out: “How To Zero A Deer Rifle“. It gives the shooter a basic awareness of the factors required in a proper Zero for. BadAss Optic takes the shooter, with any level of skill, through every detail of a Zero at 100 yards.

The 20 MOA rail raises the angle of the bore upwards, causing the bullet travel to arc higher in relation to the scope's line of sight. The result is a higher point of impact at 100 yards. The shooter must adjust elevation down to reach zero.

When the shooter backs off to longer distances, the additional elevation is now available for more up correction.

Ring height and Rifle scope Cant

Sharpshooters recommend placing the objective lens of your rifle scope as tight to the rifle barrel as possible.

The reason for this, the flight track of your bullet will be as close to the crosshairs as possible. This basic configuration eliminates or minimizes holdover/holdunder.

If you have questions about scope ring height, use this excellent Scope Ring Height Calculator to find what the optimum clearances should be. Add your objective lens size and your type of scope ring, and Mil-Rad calculates the ideal height.

barrett exrings pin lock extended range scope rings
Referenced AccurateShooter.com

Sometimes you need higher mounts and/or rings to bring the centerline of your scope in line with your eye.

A common reason why there is misalignment, the rifle may have a higher cheekpiece, and finding the ideal head position is difficult.

Another reason that may affect a higher mount or rings is the clearance of the rifle barrel and the bottom of the scope.

long range precision rifle match setup

Scope builders use different materials that are thicker, so the objective lens diameter may be closer than the shooter wants. Another issue, opening the bolt on a bolt-action rifle can interfere with the ocular lens of the scope.

Adjustable scope mounts and rings provide clearance or tightness to sidestep a lot of scope mounting troubles.

Check Out: Best 34mm Scope Rings or Best 30mm Scope Rings

Drawbacks and Problems With A 20 MOA Base

  • With a few lower quality scopes, shooters experience added parallax
  • A 20 ⦁ MOA base puts the eye piece fairly high, so there may be some comfort issues shooting from the prone position.
  • Make certain the scope does not have too much forward cant for the position you wish to shoot.
  • Some scope builders report too much negative adjustment with a 20 MOA base.
  • A few shooters have said, they are ⦁ running out of MOA elevation adjustment


Nothing beats the thrill of seeing a shot made at 1000 yards or more. Modern equipment has advanced well past the natural capabilities of most shooters. There are few paces on earth that allow hunters to test their skills at these extreme distances. Yet, technologies keep adding to these insane distances.

The sport of extreme long-distance shooting is growing in popularity across the world with ranges starting at 1500 yards. Once a marksman hits a target at 2500 yards it is hard to control the enthusiasm.

Barrels are reaching 32 inches in length, calibers are heading north of the .375 CheyTac, and it costs nearly $8 dollars a round. A well built long-range targeting rig can cost conservatively $5,000.00

The 20 MOA base and rail are now common place in the world of hunting. Many shooters opt for the equipment, whether they need it or not.

It is an exciting time in firearms and long-distance shooting. As long as the equipment continues to advance, there will be shooters who push the extremes.