Spuhr Offset Scope Mount, 34 mm / 38 mm / 0 MOA / 70 mm Offset Gen 3

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On an AR upper, it’s not the total length of the rail that matters, but the section that really belongs to the rigid receiver. If a scope needs to be mounted far forward for the correct eye relief, the mounting base still must not be half on the receiver and half on the handguard. This is exactly where a well-planned optic system differs from a solution that only fits visually.

The SP-4022C shifts the rings 70 mm forward with its extended cantilever. At the same time, it sets the optical axis 38 mm above the rail, corresponding to what Spuhr calls the Absolute Co-Witness AR height. The Gen-3 geometry creates more distance between the rings and shortens the rear ring so that many scopes with longer adjustment turret housings also fit.

What must match before ordering: Weapon side: a continuous, sturdy Picatinny or STANAG rail on the receiver. Mounting: firmly screwed SP-4022C with 70 mm cantilever. Optic side: 34 mm main tube with matching straight clamping surfaces. Ergonomics: 38 mm axis height, real objective outer diameter, and required eye relief. Additionally required: scope, torque tool, and a subsequent complete zero check.

SP-4022C: Gen3, but not the M-reinforced SP-4022CM
The live version is clearly SP-4022C. The C suffix marks Gen3 at Spuhr; for 34 mm mounts, this includes a larger ring spacing. The additional M in SP-4022CM, however, marks a reinforced heavy-duty version. C and CM are therefore not interchangeable model names.
The values of the exact C datasheet apply to this SP-4022C: 242 g, seven interface sets, 38 mm axis height, and no integrated bubble level. Weight or clamping details of an SP-4022CM are not transferred to this product. Anyone explicitly looking for the M-reinforced version needs a correspondingly marked mount.

The long cantilever solves a receiver problem
The complete rail clamping remains on the upper receiver, while the two rings stand significantly further forward. This allows a scope to be adapted to a longer stock position or a dynamic cheek weld without distributing the mechanical base over two separate parts. Loads on the handguard from bipod, sling, or barricade thus do not act directly on an optic clamp located there.
However, the long cantilever is not an automatic upgrade. It makes sense if the correct eye relief cannot be achieved with a block mount or a shorter cantilever. If the natural head position is already further back, the SP-4022C can create too much offset or unnecessarily occupy rail space in front of the optic.

What Gen 3 really changes in this mount
The C in the model name marks the Gen-3 version at Spuhr. For the 34 mm mounts, the distance between the rings was increased; the SP-4022C also has a shorter rear ring. The practical benefit lies in more free housing length around the adjustment turret and thus a better chance to neatly accommodate modern scopes with extended erector housings.
The exact model datasheet explicitly states
also many US-Optics versions with TPAL or EREK housing as compatible. However, this does not imply universal fit. Intermediate tube transitions, turret block, illumination module, and the actually available straight clamping zones must still match the fixed ring positions on the specific scope.

38 mm axis height: head position, co-witness term and installation space
Spuhr measures from the top edge of the rail to the optical center axis. 38 mm or 1.5 inches corresponds to an AR-typical sight line and supports a more upright head position than the low 32 mm SP-4026. The cheek weld must remain reproducible; on a classic stock, the same height can already be too high.
“Absolute Co-Witness” here describes the shared height level with AR sights. A magnifying scope does not automatically make mechanical sights usable through the optic. Field of view, eyepiece, and flip-up sight determine whether the backup sight can only be used after removing the mount or in another configuration.
For objective clearance, the real outer diameter including protective cap counts. Above a rail or handguard level of the same height, 38 mm axis height theoretically allows a maximum outer diameter of 76 mm with zero clearance. If the housing measures 64 mm, 6 mm of clearance remain; if the cap adds up to 68 mm, 4 mm remain. These are calculation examples, not measurements of a specific scope.
The formula is: 38 mm minus half the outer diameter minus protrusion under the objective. Higher handguard areas, accessory rails, and desired safety clearance are additionally subtracted. Objective class and outer diameter must not be equated.

0 MOA keeps the mount neutral
No additional forward tilt is built in between the front and rear ring. The mount therefore does not shift the usable elevation adjustment range of the scope in favor of longer distances. This fits setups that can be zeroed safely on their existing rail without an additional tilt angle.
If an inclined rail is already mounted, its angle naturally remains part of the system. Before an alternative with forward tilt, rail, mount, internal adjustment range, and desired zero distance are considered together. More tilt only makes sense if the optic can actually use it.

Why no bubble level is integrated
The datasheet cites the extreme cantilever design as the reason why the SP-4022C does not have an integrated bubble level. This point distinguishes it from many block mounts of the ISMS family and is decisive for precision applications. Anyone who wants to check canting immediately must consciously plan an external solution.
For this, the mount has seven sets of the Spuhr accessory interface. They can accept suitable direct interfaces or short rails. The interface surfaces on the ring tops follow the scope axis; surfaces on the mount body follow the rail base. This is more important for secondary optics, lasers, or angle indicators than any arbitrary free hole.

Construction, screws and delivery condition
Spuhr manufactures the mount body according to the model datasheet from a billet of the 7000 series aluminum and coats the aluminum parts with a hard anodized surface. The rings are diagonally split so that the screws interfere less with view and access to elevation and windage turrets. Ring and clamping screws are corrosion-protected and waxed from the factory.
The fixed rail clamp has no QD lever. According to the current ISMS instructions, the mount is pressed forward against the rail slot when mounted; the clamping screws receive 5 Nm. For the ring screws, Spuhr specifies 2.0 Nm or the lower value of the optic manufacturer. Additional lubrication or thread locking changes the preload and should not be applied unchecked to the waxed screws.
Our Assessment
The SP-4022C is strong when three requirements apply simultaneously: 34 mm main tube, 38 mm AR height, and a ring position needed very far forward. The larger Gen3 ring spacing and the shorter rear ring solve a real problem of modern scope mounts without shifting the mounting base onto the handguard.
The long cantilever remains a special geometry. Those who achieve the eye relief with 40 mm forward offset carry unnecessary length in front of the base. Those who deliberately shoot low are better served with 32 mm. And those expecting heavy-duty M-reinforcement or an integrated bubble level should look for another model. With suitable optic and shooting geometry, the SP-4022C is a convincing Gen3 premium solution.

Instructor Tip: Determine the 70 mm cantilever only after the stock length Set the stock for the actual shooting position with safety glasses and hearing protection. Hold the scope at the highest regularly used magnification so that the full field of view appears without head movement. Only this position shows whether the extended cantilever is needed. If the mount is chosen first, the shooter often compensates for too much forward offset later with an unnatural head position.

User Tip: Keep the entire clamping on the upper receiver The cantilever carries the rings forward; the base itself remains fully on the receiver. Even with visually flush rails, no clamping screw is placed on the handguard. This keeps the optic position independent of load, disassembly, or minimal movement of the handguard.

User Tip: Do not confuse Gen3 ring spacing with universal fit Place the scope loosely in the opened rings and use only fully cylindrical clamping surfaces. The shorter rear ring creates space next to longer turret housings but does not allow clamping on a cone or housing transition. Illumination module, magnification ring, and throw lever must remain free over their entire range.

User Tip: Measure accessory screws before installation With Spuhr interfaces, not only the thread is decisive. A screw that is too long can reach the scope. Use the length gauge on the back of the supplied wedge and check each accessory pair before pressure is applied to the main tube.

User Tip: Document zero point and screw marks together After correct tightening, mark the position of the clamping screws on the existing index marks. Also note the rail slot used. After disassembly, the same mechanical starting position can be restored; the zero point is still confirmed before the setup is used again definitively.

Black-Raptor Short Summary: Buy if: a 34 mm scope must be clearly forward on an AR receiver, 38 mm axis height fits the shooting position, and the extended Gen-3 ring geometry provides real space gain. Do not buy if: a low sight line, integrated bubble level, QD function, additional forward tilt, or only short forward offset is needed.

Scope of Delivery

Spuhr SP-4022C Gen-3 Cantilever Mount
Spuhr leveling wedge with 10-degree angle
Manufacturer’s manual

Not included: scope, firearm, torque tool, external bubble level, and other Spuhr interface accessories.

Suitable alternatives by tube size and geometry:
Lower 34 mm version with the same long forward offset
Same height and forward offset for 30 mm main tubes
Compact 34 mm Gen-3 block mount without long cantilever
34 mm QD alternative with shorter forward offset

Technical Data


Manufacturer: Spuhr

Model: SP-4022C

Generation: Gen 3

Design: one-piece fixed extended cantilever mount

Weapon interface: Picatinny / STANAG

Main tube: 34 mm

Axis height over rail: 38 mm

Calculated outer diameter limit: 76 mm over an equally high rail/handguard plane at zero clearance; caps, desired clearance and overhang
de reduce this value

Tilt forward: 0 MIL / 0 MOA

Offset forward: 70 mm

Overall length: 140 mm

Weight: 242 g according to SP-4022C model datasheet

Material: 7000 series aluminum according to manufacturer

Surface: hard anodized

Accessory interfaces: seven Spuhr interface sets

Integrated bubble level: no

Quick release function: no

Torque for rail clamp: 5 Nm

Torque for ring screws: 2.0 Nm or lower release by the optics manufacturer

FAQ
How does the SP-4022C differ from the low SP-4026? The SP-4022C sets the optical axis at 38 mm and is designed by Spuhr for the AR-typical Absolute Co-Witness height. The lower alternative also uses a long cantilever but requires a significantly different head position.
Does a scope with extended turret housing fit? Many such 34 mm optics fit according to the model datasheet, including TPAL-/EREK versions from US Optics. There is no blanket guarantee; especially clamping zones and turret block must be checked against the fixed ring positions.
Does the mount have an integrated bubble level? No. Spuhr cites the extreme cantilever as the reason for omission. Tilt control must be planned separately with a compatible interface if needed.
Is the SP-4022C a quick release mount? No. It is firmly mounted on the rail with Torx clamping screws. For frequent tool-free changes, a suitable QD version is the more honest choice.
What does 0 MOA mean? The mount has no additional tilt forward. It does not shift the internal elevation adjustment range of the scope; any tilt of the existing rail remains unaffected.
How is the objective clearance at 38 mm height calculated? Half the actual outer diameter including protective cap is subtracted from the 38 mm axis distance. The result is the clearance to an equally high plane. Higher handguard areas, accessories, and desired safety distance are subtracted additionally.