Everything to Consider When Deciding How High to Mount Your Rifle Sight
The optimum height for a sight to be mounted on a rifle for maximum performance depends on many factors.
First, the compressed version.
Advantages of a Higher Sight:
Won’t interfere with earmuffs as much or at all.
Won’t interfere with gas masks as much or at all.
Allows for a more comfortable neck and head position.
Creates smaller elevation adjustments at longer ranges.
Easier to keep the line of sight clear.
Greater field of view with NVGs while using the sight.
Often easier to use with glasses.
Can give more clearance to operate charging handles and bolts.
Allows better visibility over the rifle while using the sight.
Advantages of a Lower Sight:
Less cant error.
Smaller height over bore adjustments at close ranges.
Better cheek weld.
Allows use of the sights through smaller holes or gaps in objects.
Allows your head to be exposed less.
Easier to store and transport.
Now, the explanation.
The value you place on each of these factors will depend on your rifle, your body, any gear you're wearing, your preferences, the type of shooting you will be doing the most and how important certain types of shooting will be for you.
Earmuffs
Whether you will be able to use your sight without your stock smacking or pushing up your earmuffs depends on your body, type of stock and stock placement. Generally, if your earmuffs sit really low on your ears because the headband is too big, sights that are lower than about 3” - 3.25” will contact stocks that aren’t dropped below the sight mounting surface. Generally, if your earmuffs sit centered or high on your ears, sights that are about 2.8” and higher won’t contact the stock.
Gas Masks
Your ability to use your sight with a gas mask will depend entirely upon the type of mask you have, but extremely low sights will often be impossible to use and sights that are really high can often allow you to shoot as you naturally would, if you don’t have a filter on the side you’re shooting with.
Head Position
The height of your sight and how low you place your stock on your body will determine how much you have to drop your head down, which will effect neck fatigue and your vertical field of view. If you place your stock low on your body, when standing straight, a sight around 5” is in a natural position, not inducing any neck fatigue. When leaning/hunching forward significantly, a sight around 3” will be in a natural position. If you place your stock higher on your body or closer to the edge of your body, a lower sight will be in a natural position. When prone, your body, any gear you’re wearing and the height above the ground your rifle sits will significantly effect what sight height is the most comfortable and allows your eyes enough visibility of your surroundings without straining them. The lower to the ground your sight is, the less you have to hold your head up or arch your back, but your eyes will be looking out of the top of the sockets, which will strain them and limit your ability to see higher elevations.
Elevation Adjustments
Because of the relative angles of the line of sight and path of the bullet, a higher sight will result in less bullet drop relative to the point of aim, so if you want to minimize the value of longer range bullet drop corrections and errors caused by range estimation inaccuracies, a higher sight will help you.
Keeping the Line of Sight Clear
If you plan to shoot with any fingers on the top of the handguard, mount something to it, or use ghillie materials, especially closer to the muzzle, a higher sight will allow more room before it’s field of view or line of sight will be blocked.
Field of View with NVGs
When you drop your head down to use your sight, your eyes have to shift up to continue looking straight. When you wear NVGs, the tubes can’t shift up so the more you have to angle your head down, the more the NVGs will be looking down and your FOV will drop down. Higher sights allow your head to stay straighter and maintain your ability to see into the regions above your point of aim.
Glasses
Whether the top of your glasses interferes with your ability to use your sight completely depends on your glasses, how you wear them, your head and how high you place your stock on your body. More often than not, having a higher sight will keep the top of your glasses from getting in the way of using your sight for the same reason that NVGs are more difficult to use with lower sights.
Charging Handle and Bolt Clearance
A large sight that is mounted near the bolt of a bolt action rifle or the charging handle of a semi auto or automatic rifle can make it more difficult to operate. Mounting the sight higher will usually give more clearance to operate the rifle.
Visibility Over the Rifle
The higher your sight is, the lower your rifle is compared to your eye while you’re using your sight, so the part of your vision that is blocked by your rifle is lower. If you have both eyes open, your sight shouldn’t be blocking any of your vision unless you have a scope. Your head is still able to rise up to the same height to see over your rifle regardless of sight height unless you place your stock higher on your body to assist.
Rifle Cant Error
Firing with your rifle canted can cause significant differences in the point of aim and point of impact of your bullets at long range and the higher your sight is above your barrel, the greater this difference will be.
Close Range Height Over Bore Adjustments
The height of your sight has to be corrected for at close ranges, so a higher sight will make achieving precise shot placement and shooting over the top of objects at close ranges more difficult.
Cheek Weld
When your sight is low enough that you can get a good cheek weld, it’ll be easier to repeatedly get your eye straight behind your sight quickly. If your sight is low enough that your face is really resting on your stock, it’ll reduce neck strain, which is nice when you’re set up somewhere for a long time. If your sight is so high that no part of your face touches the stock, it’ll take more time to get used to the exact head vs stock placement needed to line up with the sight.
Firing Through Gaps
A lower sight allows you to use your sight and fire through a smaller hole or gap in the environment that is close to you. Higher sights allow you to use your sights over smaller obstructions like vegetation and fire under it, so whether this is something worth considering is up to how you plan to use your rifle.
Head Exposure
With a lower sight, when prone or firing over top of cover or concealment, your head doesn’t have to stick up as far, keeping you more concealed and protected from dangers. The rifle can be turned sideways to reduce head exposure but will only be effective at closer ranges due to the extreme cant error that will be created.
Storage and Transportation
A higher sight will make a rifle take up more room and make it harder to fit in bags and other transport and storage areas.
Bonus Consideration
An additional thing to consider is if you want to be able to mount a magnifier or a night vision or thermal device on the rail behind or in front of a sight, the sight has to be mounted at a height that the other device will be able to line up with.
If you already have the rifle the sight will be going on, or have a similar one, test how it would be with a sight at different heights used in as many situations as you can think of. If you’re already used to a certain height, remember that a change will take some time to get used to and may not seem as good at first, but may end up being better for you once you become accustomed to it. Taking into consideration the information explained here and your particular situation, you should be able to find the optimal height to mount your sight.