How to install Swiss K-31 rifle Grunel sights

The Swiss k31 is an excellent rifle, and arguably the most accurate of the military surplus rifles available. I could go on and on about their quality, craftsmanship and accuracy. If there is any shortcoming with the rifle it is in the stock issued iron sights. With no real click-able adjustment on the fronts or rears, there have been several aftermarket options available through the past decades.

There are Diopter sights if you have a few hundred dollars laying around with nothing to do, but I decided to try the Grunel sights as they have fine-tunable adjustment (1 CM clicks at 100M) and retain the appearance or the original issued rifle. Before getting started  you will need a little brass punch set. This prevents marring of the metal and finish when tapping out the pin and front sights.
Masen Brass Hammer & Punch Set - Brass Punch Set

The previous owner of my rifle had installed the Mojo sights. These are excellent sights. Aperture sights use sound holes which can be much easier to align especially if you do not have perfect vision. However, the windage is not ‘clickable’ and it can be difficult to determine how much elevation each click provides.

k31s03

So to get started, a small non marring clamp and piece of wood is needed to press the spring under the rear leaf sight. The same process is used for the stock sight.clamp

Once the pressure from the spring is held down, use a little punch and gently tap the hinge pin out.
pin2

This is the rear of the Grunel sight, from below. The elevation adjustment is achieved by this sliding piece lifting against the rear sight base:
k31s05

The front sight slips right over the end of the barrel against the stock base. You can even make gross front sight height adjustments by loosening the set screw and manually adjusting the blade height.
k31s01

For the rear sight, slide the adjuster off of the original sight, and put the rear sight leaf into the Grunel assembly and tighten the side screw to hold it in place.
k31s06

Installation is essentially the reverse of removal. Line up the assembled rear leaf and gently tap the pin back in:
pin3

Ready for the range! The top wheel adjusts windage and the lower adjust elevation. This is much easier than trying to tap a front sight around trying to adjust for elevation when you just need a fast change.
k11

I set the windage in the middle best I could, and set the elevation all the way down and was very happy with the first shot!

 

k312
@50m, the first shot landed on the left of the bullseye! I adjusted the windage 4 clicks over and it landed on the right. A couple clicks back and it’s just fine! Windage adjustments with a couple clicks that take a second or two is definitely better than having to tap the front post around at the range.

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3 Responses to How to install Swiss K-31 rifle Grunel sights

  1. Allan says:

    G’day,
    Just curious, you mentioned used a brass punch and then in the picture you used the steel punch. Was the brass not sufficient?

  2. admin says:

    Holy cow, someone read this? There wasn’t a small enough brass one. A finishing nail would probably do fine too: Use the flat end against the pin.

  3. Allan says:

    I reckon thousands have read this. Any info on doing is good info. Especially detailed info such as presented here. Many thanks for documenting it. Just waiting for my brass punch set to arrive and will install a Mojo on one and an S&K mount on the other.
    Many thanks.
    Allan.