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Gunsmithing Rifles

How to Mount a Scope on a Swiss K31

by Gus Norcross   |  July 31st, 2013 5

I think most of you will agree that standing on a range hammering targets with an accurate bolt-action rifle is a lot of fun. My favorite rifle for this activity is the Swiss K31. Very accurate with a good trigger, and weighing less than 9 pounds unloaded, these are slick weapons readily available on the surplus market. My only serious gripe about the K31 is that I can’t see the sights very well, and if you’re not hitting the target, where is the fun in shooting? The barrel-mounted tangent rear sight might have worked for me in the ‘70s but no more. This rifle screams for either a receiver mounted peep sight or a scope.

Fitting a peep sight would require drilling and tapping holes in the receiver, and I’m not quite ready to make permanent modifications to this rifle. So I looked at scope mounts. Due to its vertical ejection pattern a scope can’t be mounted directly over the top of the receiver loading port. That leaves us with either a side mount or a “scout” type mount forward of the receiver. I have tried the side mounts from Swiss Products. They sell a permanent mount that screws to the left side of the receiver, which is quite solid but it requires drilling and tapping three holes. OK for a sporter, but doesn’t fit my criteria of no permanent alterations. The same company produces a clamp-on side mount which attaches to the right side of the receiver that works quite well. I set up a rifle with a 2-7X Leupold VX-1 and the clamp-on side mount (see pics). It worked fine except for a few brass marks on the scope body, and the slight offset of the scope to the right of bore centerline was hardly noticeable when shooting.

I was relatively satisfied with the side mount setup, but one day the nice people at Hi-Lux Optics sent me a new scope to evaluate. It is similar to the 2-7×32 scout scope I previously tested on the Garand but with a new .308 BDC reticle. When someone sends me a product to test I feel obligated to do so and I contemplated my options. Looking through the Brownells catalog, I came upon the S&K “Insta Scout Mount” for the K31.  The S&K mount replaces the rear sight, attaching securely to the rear sight base and provides 4 3/4 inches of Weaver style rail forward of the receiver. Attaching the steel S&K mount was a snap and I mounted the scope to the rail with Burris Zee rings to keep it as low as possible.

Minimum eye relief of the Hi-Lux scope is 8.7″ at 7X and is perfect for the K31. Most scout scopes are low power optics good for a quick shot at shorter ranges but not so good for target shooting at distance. With a variable power scope like the Hi-Lux I have the best of both worlds. I can turn it down to 2X and hammer targets off-hand at 50 yards or I can sit at the bench at 100 yards and test my handloads at 7X. The .308 BDC reticle is designed to be zeroed at 200 yards—center of crosshair—with hold-over marks for 300, 400 and 500 yards. The 7.5 x 55 K31 actually fires a .308-caliber bullet, although the brass casing differs from our own .308 Win and ballistics of the two cartridges are similar enough that I believe the reticle will work in this application.

Zeroing the scope was quick and easy with the finger adjustable elevation and windage knobs, although I found the knobs a bit stiff to operate. Once the rifle was zeroed, I loosened the two screws on each knob and zeroed the scales. The knobs provide positive, audible ¼ MOA clicks and are capped when not in use.

With the Hi-Lux scope, I was able to shoot sub MOA groups off the bench at 100 yards relatively easily firing Swiss 174-grain FMJ ammo dated 1978. A K31 is generally very accurate, and the addition of a good scope allows the marksman to shoot the rifle to its potential.

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