EXPLAINING THE ISMS MODEL MARKINGS

Most items from Spuhr are marked with a model number and a batch number. When ordering please refer to the model numbers.

Scope mounts are marked with a model number consisting of two letters followed by four digits. However, there are three exceptions to this rule where there is a total of five digits as well as some models featuring a suffix.

The batch numbers consist of four letters. Old batch numbers consisted of a single letter followed by four numbers; for example M-1204 or M12/04, where the numbers indicate year and month.

The two letters identify the type/firearm/rail the mount is designed for:
SA - Scope mount Accuracy International (11mm dovetail)
SP - Scope mount Picatinny
SS - Scope mount Sauer (for Sauer SSG and STR rifles)
ST - Scope mount TRG (17 mm dovetail)
SR - Scope Rings (separate rings for Picatinny rail)

The first digit identifies tube diameter:
3 - 30 mm tube
4 - 34 mm tube
5 - 35 mm tube
6 - 36 mm tube
7 - 40 mm tube

The second digit identifies tilt:
0 - 0 tilt
3 - 3 MIL/10.3 MOA
6 - 6 MIL/20.6 MOA
7 - 7 MIL/24 MOA tilt
8 - 13 MIL/44.4 MOA and 11 MIL/40 MOA
9 - 9 MIL/31 MOA

Note: The SP-61602 and SP-41808 feature two digits for tilt: 16, indicating a tilt of 16 MIL/55 MOA, and 18, indicating 18 MIL/61.8 MOA.

The third digit is for special versions:
1 - Cantilever mount
2 - Extended cantilever mount
3 - Short rear top cover for the S&B Ultra Short

The fourth digit identifies height:
1 - 30 mm / 1.18"
2 - 38 mm / 1.50"
4 - 48 mm / 1.73"
6 - 34 mm / 1.35"
8 - 44 mm / 1.73"

Note: The height is always measured from the top of the rail to the centerline of the optics. On a tilted mount the measurement is made at the back plane of the rear ring.

B suffix
Some mounts feature a B suffix following the model number. In the ISMS line this indicates an extra-long mount for scopes with extended length erector housings, such as the U.S. Optics TPAL and the NightForce B.E.A.S.T.
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Pro Tip: Use a paint marker on your scope mount

There is nothing worse than suddenly realizing your scope mount has come loose in the field and you've lost your zero. Quality scope mounts like the Spuhr AB Seekins Precision or Badger Ordnance mounts that are properly torqued down go a long way towards preventing that from happening. A cheap back up is to use a paint marker and index all the screws on your mount. As soon as something comes loose you'll have a visual indication that there's a problem. Placing a mark on the body of the scope also allows you to identify where the scope was mounted when it was level and at the proper eye relief. This comes in handy if you end up in a situation where you need to turn the mount around. Ask me how I know...

Some shooters prefer not to paint their scopes during classes and I completely respect that, when you've paid upwards of $2500.00 for a scope most guys don't want to paint little red lines all over it. To each their own, personally I'll take the added insurance and peace of mind that I get with indicators like paint markers. Besides I don't believe in safe queens and scars add character.

Shooter: Alexandra I Wilson
Rifle: Barrett 98B
Mount: Spuhr ISMS
Scope: Leupold Optics MK4 4.5-14 FFP
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Stay tuned for a series of videos on the "How To" build out your AR-15 from Optics Planet. Geissele Automatics, LLC ALG Defense 5.11 Tactical Nosler Spuhr AB Vortex Optics STI International 3-Gun Nation BOOMFAB Invictus Practical ... See MoreSee Less

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