Spuhr ISMS ST-6401 Ø36mm Tube 4 MIL (30mm High) Sako TRG Scope Mount

• Ring Size 36 mm
• Tilt 4 MIL / 14 MOA
• Height 35 mm / 1.38"
• Clearance 6 mm / 0.236" (from bottom of tube to bridge of mount body)
• Length 126 mm / 4.96"
• Weight 245 g / 8.6 oz
• Interfaces 7 sets
• Material 7075 T651 aluminium, hardcoat anodised
• Screws Torx 20, zinc-nickel coated, pre-waxed
• Included Adjustable recoil screw, 10° wedge levelling key, manual
• Compatibility SAKO TRG-22, TRG-42, and Tikka T3x dovetail rifles
• Objective Clearance Designed for scopes with up to 56 mm objective lenses

• Direct dovetail fit for SAKO TRG-22, TRG-42 and Tikka T3x rifles, eliminating the need for additional rails.

• Integrated bubble level at the rear of the mount to ensure correct rifle alignment and prevent canting errors.

• Seven accessory interface points allowing attachment of over 40 different accessories from the Spuhr ISMS system.

• Diagonally cut rings that improve visibility of elevation and windage turrets without compromising strength.

• 7075 T651 billet aluminium construction for maximum durability with reduced weight.

• Hardcoat anodised finish for long-lasting surface protection.

• Zinc-nickel coated Torx 20 screws that resist corrosion in all weather conditions.

• Pre-waxed screws from the factory for consistent and secure torque application.

• Adjustable recoil screw included for enhanced stability under heavy recoil.

• 10-degree wedge levelling key supplied for quick and precise scope alignment.

• Designed for long-range performance, offering improved scope positioning and stability.

• Spuhr Aluminium One-Piece 36mm Dovetail Rifle Scope Mount - 14MOA

Why is a one-piece dovetail mount mechanically superior to split rings on a dovetail rail?
Split rings rely on the rail to align them; the ST-6401 does not. Because both rings are machined in the same fixture, their bores are perfectly coaxial. This prevents the scope tube from being forced into a bend when torqued down — a common cause of tracking errors.

How does the ST-6401 prevent scope tube ovalisation?
Spuhr machines the ring bores after anodizing so the internal diameter is exact. This ensures uniform radial pressure instead of point-loading, which can distort thin-wall 36 mm tubes and damage erector assemblies.

What role does the 14 MOA cant play in optical performance, not just ballistic reach?
By shifting the scope’s mechanical zero downward, the erector assembly operates closer to its optical center. This improves tracking linearity, minimizes optical distortion, and keeps parallax behavior more predictable at distance.

Does the ST-6401 reduce the need for shimming or bedding on dovetail rifles?
Yes. The mount’s base geometry is cut square to the ring axis, so the optic is already aligned to the dovetail’s reference plane, eliminating the need for corrective shims used on less precise mounts.

How does dovetail engagement differ from Picatinny recoil lugs?
Instead of a single recoil stop, the dovetail interface distributes recoil forces across the full length of the angled rail faces. This reduces micro-movement under recoil and prevents peening of a single lug.

Is the ST-6401 more tolerant of rail wear than separate rings?
Yes. Because it clamps across a long dovetail surface rather than two isolated points, wear on the rail is spread out, preserving alignment even after thousands of rounds.

How does this mount affect barrel harmonics?
The one-piece body resists torsional flex, so the scope mass does not oscillate independently of the action. This reduces tiny shifts in point-of-impact caused by optic mass reacting to barrel whip.

Can this mount support clip-on night-vision or thermal units?
Yes. The rigid, monolithic body keeps the scope’s optical axis stable relative to the bore, which is critical when using inline devices that depend on precise optical alignment.

Does the 14 MOA cant change how zeroing is performed?
Yes. Zeroing will occur with the elevation turret dialed slightly downward relative to mechanical center, which gives you more upward travel for long-range dialing while maintaining optical symmetry.

Why is this mount preferred on high-magnification 36 mm scopes?
Large-tube scopes have heavy erector assemblies. The ST-6401’s ring spacing and rigidity prevent tube flex that would otherwise degrade tracking and cause zero drift during recoil.

How does the ST-6401 handle temperature-induced zero shift?
The mount’s aluminum alloy is stress-relieved and anodized, reducing internal stresses that cause warping when temperatures swing from cold to hot firing conditions.

Why is ring spacing important on this model?
The ST-6401 spreads the rings far enough apart to stabilize long scope bodies, reducing bending moments on the tube when firing heavy recoiling cartridges.