Rugged, stable, machined perfection, and repeatable. These are the first words that come to mind when describing the SPUHR ISMS single piece mount. Specifically the SPUHR ISMS SP-4006. This article will be an overview of the Spuhr ISMS single piece scope mount, including an install of an Arken EP-4 Optic we have in for review. The SP-4006 model works with 34mm scope tubes and has a zero MOA cant. The mount weighs 8.4 oz and is machined from billet 7075 T651 aluminum, and all aluminum parts are hardened and anodized. The Torx T20 base and ring screws are zinc-nickel coated for corrosion resistance.
ISMS stands for Ideal Scope Mounting System. After using these mounts on several rifles it truly lives up to the name. Let’s discuss some of the features.
One of the first things you notice about the mount are the extra holes for accessories. The SPUHR designers realized that serious shooters sometimes have a desire to use additional components. These may include a level, RMR, rangefinder, laser, or lights. This mount allows the user to attach these items directly or with the use of adapters, such as picatinny rails, sold by SPUHR.
One of the small, yet very useful features that is also added, is the integrated bubble level. This bubble sits at the rear/bottom of the base and is visible with a quick glance while shooting. The standard level is white but a green level is also available for purchase. On the .308 rifle in the images, the bubble level was clearly visible and eliminated the need for a scope mounted and pic rail level.
The SP-4006 mount uses 6 Torx T20 screws per ring! Talk about rugged. These screws come pre-waxed from SPUHR to ensure perfect torque values. The torque setting for the rings is determined by your optic manufacturer. The very best way to ensure you have the proper torque values is to pick up a set of Fix-It-Sticks. I used their 45 in-lb torque limiter on the 4 base screws and 15 in-lb torque limiter on the 12 ring screws. The rings are also wider than many other rings on the market, which provides more than ample contact surface so scope movement is a thing of the past.
As an added feature, in case the included twelve scope ring screws isn’t enough to hold your scope firmly and you want to go the extra mile, the SPUHR mount can accommodate your wishes. These mounts have finely machined channels on the inside of the rings where one can apply a small amount of Powdered Rosin. I personally have never used the rosin, but I have also never had a scope move after it was mounted either. Either way, it is there in case you need it!
Mounting the SPUHR to your rifle is extremely easy. The four base screws are numbered in the order in which you should tighten the T20 screws to 45 in-lbs to prevent any binding.
I have discussed many of the features included in this mount, but lets get to one of my favorites. The SPUHR mounts ae shipped with a “wedge” leveling key. This wedge is inserted into a channel in the mount base. The top, or flat side, of the wedge will contact the flat bottom of the turret housing. While tightening the rings, this wedge will ensure the scope reticle is mounted perpendicular to the picatinny and scope base. This increases the speed and effectiveness of the scope mounting procedure.
Within the first sentence of this article, I mentioned that repeatability was one of the features of this mount. You may have thought, “How does repeatability apply to a scope mount?”. Many of us understand the feeling that comes from paying a large amount of money for a superior optic. It goes with the territory, when acquiring very good glass. However, when it comes time for our next rifle purchase, we tend to look at it reluctantly. We take into consideration the fact that any new rifle will need a new optic, so the costs really start to add up. Add the need to convince the wife on why we need another optic and we tend to hold back on the new rifle. Whatever the case may be, the SPUHR ISMS helps with this new rifle/optic consideration. The reason is, this mount can be removed from one rifle and placed on another with the quick removal of the four base screws. I have personally taken this optic (after a zero was obtained), moved it to a different rifle, shot a match, returned it to the original rifle, adjusted the turrets back to the original settings, and confirmed my 100 yard zero. It was a quick process and proved out that this base is made to be easily moved from one rifle to another. Repeatability.
If you are looking for, the Ideal, wait scratch that; the “Perfect Scope Mounting System”, save yourself the time and look at a SPUHR mount. You cannot go wrong. Btw, maybe that will catch on, the SPUHR PSMS?
To see the full line of SPUHR Mounts and accessories, head over to Mile High Shooting.