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 (if other than 0) is for special versions:
1 – Cantilever mount
2 – Extended-length cantilever mount
3 – Short rear top cover for the S&B Ultra Short
4 – Medium-height cantilever mount
The fourth digit identifies height:
1 – 30 mm / 1.18″
2 – 38 mm / 1.5″
4 – 48 mm / 1.89″
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.
B suffix
Some older mounts featured 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.
C suffix
Some mounts feature a C suffix following the model number. This denotes a Gen3 mount which has either an updated side clamp design or (for all 34 mm mounts) an increased distance between the rings, using an A-40B rear top cover, or both.
Cantilever Mounts
We currently offer three heights for our cantilever mounts. We offer two types of cantilever design: a 40 mm/1.57″ cantilever and a 70 mm/2.75″ extended cantilever. Mounts with a 1 or 4 as a third digit in the model number feature the 40 mm cantilever, whereas mounts with a 2 as the third digit feature an extended cantilever.
