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 or three 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 initial letters identify the type/firearm/rail the mount is designed for:
QDP - Quick Detachable mount Picatinny
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
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. First run of SP-4803b had 11 MIL/40 MOA tilt.
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
4 - Medium cantilever mount
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" (except for on Cantilever mounts)
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.
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.
We currently offer three heights for our cantilever mounts. The high cantilever mounts (where the third digit is a 1) are 38 mm / 1.5" high, the medium cantilever mounts (where the third digit is a 4 - currently only available as as QDP) are 36 mm/1.35" high, and the extended cantilever mounts (where the third digit is a 2) are 32 mm / 1,26" high.