Scope Mounts

Scope Mounts Frequent Asked Questions

Knowing the diameter of your rifle scope’s tube is essential. The scope mount’s rings will clamp around this tube to hold your scope firmly in place.

Most rifle scopes feature a 1-inch or 30mm main tube, but it can be difficult to tell the difference just by looking, so make sure by checking the box and user manual, searching for the scope’s specifications online, or even using a caliper to measure the diameter for yourself.

The 1-inch and 30mm 1-piece scope mounts are not interchangeable, you won’t be able to “just make it work” if the mount doesn’t match your scope.

The 35mm and 34mm scope tubes are more rare, and usually found on premium optics. There are high quality choices available for 35mm and 34mm 1-piece scope mounts, but your options will be more limited.

Some optics with non-conventional construction will feature their own proprietary mounting systems. Prism scopes like the Trijicon ACOG don’t have a space for rings to clamp onto, so the scope’s body is machined to match a detachable mount underneath.

In these cases, only products that specifically claim to match your scope should be considered. Full size ACOG mounts are a different size than mini-ACOG mounts, so make sure you are clear on which type of ACOG you are shopping for.

Sometimes scopes will utilize a modular mounting system to give users more options for their best prism scope mount. For example, the Primary Arms 2.5x, 3x, and 5x prism scopes include removable mounts for compatibility with the full size ACOG scope mount system.

The most popular mounting option for 1-piece scope mounts is the 1913 MIL-STD rail, also known as the Picatinny rail.

Based on the older “Weaver rail”, the Picatinny rail consists of evenly spaced dovetail brackets separated by slots between them.

Although they use the same overall concept, the difference between Weaver and Picatinny rails is standardization.

Weaver rails have a wide variety of slot sizes and spacing depending on manufacturer and intended use.

The Picatinny rail features consistent measurements for uniform size, shape, and spacing throughout, which must always conform with the military specification.

The Picatinny rail was adopted by the US military in the mid-1990s, and quickly became the industry standard system for attaching optics and other accessories to rifles. Almost every 1-piece scope mount uses the Picatinny rail system.

Precision bolt action rifles from Remington, Savage, Ruger and other manufacturers often come without a scope mount base installed. Other shooters may wish to upgrade their rifle’s base system from an older style to Picatinny.

It is important to note whether your rifle is a short action or a long action for proper Picatinny base fitment to the rifle’s receiver.

Pay close attention to any forward “cant” or taper purposefully built into the base, usually expressed in MOA or minutes of angle. A 0-MOA base will line up its Picatinny rail section exactly level with the barrel’s bore.

A 20-MOA base will position the rail at 20 minutes of angle relative to the bore, with the front of the base sitting slightly lower than the rear. Tapered Picatinny bases are used to ensure that the attached scope does not run out of elevation adjustment when shooting at long range.


When considering a mechanically tapered scope mount setup for a long-range rifle, be wary of combining bases and mounts that both have built in taper.

For example, attaching a 20-MOA AR-15 Picatinny mount to a 30-MOA Picatinny base mathematically combines both tapers, resulting in an extreme 50-MOA total taper.

Such an extreme angle between scope and bore could adversely affect the rifle’s ability to be sighted in correctly at shorter ranges.

While the vast majority of AR-15s on the market feature “flat top” 1913-MIL STD Picatinny rail receivers, it takes a bit more work to find the best AK-47 scope mount setup for you.

Ultimak mounts that replace the AK’s gas tube are fantastic for mounting red dot sights above the handguards, but traditional rifle scopes must be mounted further to the rear.

RS Products and Midwest Industries make excellent mounts that attach using the AK side rail often located on the left of the receiver.

These mounts curve over the dust cover to place the scope correctly in line with the shooter’s eye. Other manufacturers like Texas Weapons Systems make dust cover mounts featuring built-in Picatinny rails so optics can be placed behind the iron sights on AKs with no side rail.

Quick detach or quick release mounts are very popular among modern sporting rifle shooters. High quality quick release scope mounts allow the user to remove and reattach their scope again and again, by hand using no tools, without “losing zero” and requiring scope adjustment to get back on target.

Some users prefer quick detach mounts to store their rifles more easily without the optics attached.

Others want the ability to remove a malfunctioning scope quickly and continue shooting using back up iron sights. Finally, some shooters want the ability to swap between different scopes on the same rifle depending on the situation. Using QD scope mounts for each optic makes that flexibility possible without re-zeroing the rifle after every configuration change.

Quick release mounts generally use one or two levers in the place of thumb screws, nuts, or Allen head bolts. With the mount placed on the Picatinny rail base, the levers are turned inward, locking them in place and tensioning the mount.

Brands like American Defense, Midwest Industries, and Bobro use various methods to adjust lever tension, allowing the user to account for variations in Picatinny rail dimensions, or simply to suit personal preference. Be aware that excessive lever tension can gouge or dent the receiver rail and make the mount very difficult to remove by hand.

Non-QD mounts requiring tools to install and remove your rifle scope often cost less, weigh less, and are less bulky than similar quick detach mounts.

However, in addition to losing the advantages of tool-less quick release, budget AR-15 scope mounts are often less “repeatable” and more likely to require scope adjustments after each installation onto the rifle.

Optic height is expressed as the measurement between the top of the mounting surface and the exact centerline of the scope’s glass.

Common “AR height” 1.5-inch height AR-15 scope mounts will place your eye 1.5 inches above the top of your rifle’s Picatinny rail as you look through the scope. For reference, standard AR-15 iron sight height is just underneath that, at 1.41 inches above the rail.

One-piece scope mounts for AR-15s are so popular that it’s pretty hard to go wrong with optic height. Recently, extra tall 1.93-inch AR scope mounts have been gaining popularity.

These were originally designed so the scope’s field of view would clear bulky accessories like lasers mounted above the rifle’s handguards.

Extra tall AR-15 mounts may be more comfortable for taller shooters or shooters with bigger heads. They may also provide a minor advantage to sight acquisition speed when standing up.

However, when shooting from the prone position your cheek weld may not be as stable and repeatable with an extra tall AR mount.

The big word of caution on one-piece scope mounts is for shooters using rifles other than AR-15s. An AK or a bolt action rifle with the stock positioned significantly lower than the Picatinny mounting surface demands a mount with a much lower central height.

Installing a 1.5-inch AR height mount on a standard Remington 700 will force you to abandon your cheek weld entirely.

You will have to hold your head completely above the stock to look through the scope, and this is far from ideal. For these applications, you need to restrict yourself to looking at mount options with height measurements of 1-inch or even less. Fortunately, the proprietary Ultimak and side rail AK mounts are intentionally designed to place the scope’s centerline as low as possible.

Forward offset refers to the distance between the position of the mount’s rings compared to the position of its Picatinny rail interface area, where it physically attaches to the rifle.

Some rifles like the FN SCAR feature long sections of uninterrupted Picatinny rail, allowing the mount to be placed anywhere along the top of the rifle and making forward offset irrelevant.

However, for rifles like the AR-15 featuring handguards that are separate from the receiver, it is not desirable to place the scope mount on the handguards or use the scope mount as a “bridge” between the receiver and handguard.

A better choice is using a scope mount that only attaches to the rifle’s receiver, with enough forward offset to place the scope at the correct position relative to your eye looking through the scope.

In general, if you are using a long eye relief scope (approaching 4 inches of eye relief), you prefer a shorter length of pull style rifle stock, or you shoot with your head in a forward position in the “nose to charging handle” style, look for a “Recon scope mount” or “SPR scope mount” type with significant forward offset.

If your optic has a short eye relief (2 inches or less), you prefer a full length stock, and you shoot with your head further away from the charging handle of the rifle, then a forward offset mount won’t be needed.

When in doubt about the proper forward offset, AR-15 shooters should err on the side of too much offset, rather than not enough. If your mount doesn’t have enough forward offset when attached to the front edge of the AR-15’s receiver rail, you’ll need to extend your collapsible stock or otherwise find a way to re-position your eye further back.

It is much easier to move the scope mount a couple of slots further to the rear on the receiver due to too much forward offset.

When shopping for your best scope mount, you may be surprised by the wide variety of prices that go along with the wide variety of products. The mount’s job is to precisely attach your expensive scope to your expensive rifle in a way that will create durable, repeatable accuracy shot after shot.

A mount that loosens up or breaks can leave you out in the field with no method to accurately aim your rifle. While there certainly are budget optic mounts that will get the job done, our advice is to take your selection of 1-piece mount just as seriously as you took the selection of your rifle and scope.

If your rifle and optic are intended to function correctly in all conditions and survive some measure of accidental abuse, you don’t want the scope mount to be the weak link that lets you down and renders the rest of your investment useless.

If you are researching which 1-piece scope mount is right for your next build and you have a technical question about a product that Primary Arms carries, feel free to call 713-344-9600 or email info@primaryarms.com. Our dedicated customer service team here in Houston, Texas is standing by to help!

List of Scope Mount Manufacturers

Quick Detach Mounts

American Defense
Bobro Engineering
Burris Optics
Kinetic Development Group
Midwest Industries

Fixed Mounts

Aero Precision
Burris Optics
Daniel Defense
JP Enterprises
Leapers UTG
Nightforce Optics
Primary Arms
Sig Sauer
Vortex Optics
Warne Scope Mounts

Scope Mount Bases

Evolution Gun Works
Manticore Arms
Midwest Industries
Nightforce Optics
Seekins Precision
Tactical Solutions

AK-47 Mounts And Bases

Leapers UTG
Midwest Industries
RS Products
Texas Weapons Systems
Troy Industries

If you have any questions, don't hesitate to send us a message at info@primaryarms.com or call us at 713-344-9600.

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