What do Rifle Scope Numbers Mean?

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If you are just starting out shopping for a rifle scope, there are all kinds of numbers and terms that you may want to become familiar with. Those terms and numbers will help you navigate the sometimes-confusing world of rifle scopes.

Bushnell Elite Tactical 4.5-30X50

And, if you’re anything like me, you certainly don’t want to walk into a gun store or sporting goods store without at least understanding the common terms and numbers, so you don’t look like a newbie (even if you are). If you are not sure on certain terms, check out this post explaining some of the more common rifle scope terms.

So let’s talk about that the common rifle scope numbers mean.

Most all rifle scopes are listed by the brand, then the specific model number followed buy a series of numbers, which are usually then followed by the reticle type.

For example, take a look at this image of a box for a Sightron S-TAC 4-20X50 with an MOA-2 reticle:

STAC-4-20X50 with MOA 2 Reticle

See where it says “S-TAC 4-20X50 MOA

S-TAC would be the series or model number within the Sightron line of scopes

The first two series of numbers (which are 4-20 in this example) refer to the power range so this scope has a power or magnification range that starts at 4X power and goes all the way up to 20X power. If you see a scope with a 6-24, then it has a power range that starts at 6X power and goes all the way up to 24X power.

Sightron SIII 6-24X50 Scope

The number that follows the power range designation is the size of the ocular bell and it’s measured in millimeters. So, for the example shown above, this scope has a 50mm ocular bell.

The ocular bell size can range as low as 24mm and go all the way up to 60mm or beyond.

Here are a few more examples to help with understanding:

  • 4-12X44 – This scope would be have a power range from 4X power up to 14X power with a 44mm ocular bell.
  • 5-25X50 – This scope would have a power range that starts at 5X power and goes up to 25X power with a 50mm ocular bell.
  • 3-9X40 – A much more common designation, this scope would have a power range that started at 3X power and went up to 9X power with a 40mm ocular bell.

Another number to be familiar with is the size of the scope tube. Scope tubes can range from a tube diameter of 24mm all the way up to a scope with a 54mm or 56mm tube. However, the most common scope tube sizes are 1 inch (very common) and 30mm.

The tube size is important because you’ll need scope rings that are built to fit that specific tube. So, a scope with a 1 inch tube will need 1 inch rings and a scope built on a 30mm tube will require 30mm scope rings.

Hopefully you’ll find this information helpful when you are shopping for your next rifle scope.