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K31 - full

By Diego Cesarei

The K31and the P210 are for me the most iconic products of the Swiss weapon industry. All in, the K31 screams “Swiss Made.” The mechanics are exquisite yet simple, it’s sturdy, but elegant and the accuracy fits the stereotype of everything made in the Alps republic. Thankfully, one thing about the rifle that’s not Swiss is the price. I paid 150CHF for my 1941 K31 and a quick on-line check confirmed that the US price is pretty much the same making it a super-affordable bolt action . . .

Wait a second, did I write “bolt action”? The K31 is in fact not a bolt action but a straight pull rifle. The shooter just needs to pull and push the charging handle horizontally in order to operate the rifle. Typically a straight pull rifle is faster than a normal bolt action, but bulkier and more expensive to produce.

I bought the gun by happenstance. I was basically waiting for my Arsenal Strike One that wasn’t going to arrive any time soon and my “gun buying permit” was about to expire. Well I couldn’t let that happen, so I entered the closest gun shop and used my permission slip on the K31 because it just seemed like the right weapon to celebrate my recent relocation to Switzerland.

For the first year or so I shot it with open sights, at 300 meters from prone position (most Swiss gun clubs only allow this kind of shooting with service or former service rifles) and I started liking the rifle/caliber a lot. The results were so good that it made me wonder how good it could perform with a decent scope and a few well-placed modifications. The rifle, like a lot of other battle rifles of the same era, has a lot of potential and enough flexibility to go from hunting to SHTF weapon without flinching.

That said, a few considerations are needed. It would have been foolish to spend much more on a scope and accessories than what I spent on the rifle. Then again, it would have been a pity to take a great old gun like this and add cheap accessories. I also didn’t want to lose the gun’s fighting spirit. The K31 is no hunting rifle, it was the weapon of the Swiss militia during WWII. Yes, I know that it didn’t see much action back in the days, but it was still built for the purpose of defending one of the oldest democracies on earth, a country where each citizen is a soldier who brings his gun home after the service to be ready to repel any would-be invaders.

But what actually needed to be changed on the K31? How do you convert an old, accurate military rifle into a 21st century weapon system on a shoestring?

The K31 was designed for the needs of a better generation than the current one. Let me digress  and state an evident truth: since WWII the progressive “pussification” (as Nutnfancy would say) of the western average male is a matter of fact, what our grandfathers (and probably our grandmothers) lived through during the war is simply unconceivable for the average contemporary man.

This is to say that to my standards, the 7.5×55 Swiss round is quite punishing on the shoulder and the K31’s steel butt plate doesn’t help mitigate its kick at all. So a rubber butt plate and a muzzle brake were the first items on my list. Attaching a rail on top of the receiver would make the open sights unusable and make it impossible to employ stripper clips.  The rifle would also eject casings straight against the scope. So an offset battle ready (i.e. not clamp on) rail and a decent, yet affordable scope were next.

The K31’s two-stage trigger is OK and doesn’t need modification. Although every K31 has a sort of pillar bedding, the barrel isn’t free floating so modifications of the stock and/or bedding of the action qualified as last point in my list.

Most of the accessories I used are from the Swiss retailer of a Montana-based company called, appropriately enough, Swiss Products LLC. I think they offer the best solutions for the money and I’m very happy with what I got.

K31 - Muzzle 2

The threaded (14×1) muzzle brake is definitely effective. The company states that it should decrease felt recoil by 23%. How they came up with that precise number I don’t know, but it does the job. The quality is excellent and once installed it blends in perfectly. They offer a clamp-on version as well that’s slightly more expensive, but I felt that the threaded version was definitely the most solid alternative.

K31 - Rail

Also from Swiss products is the “drill and tap scope mount”. Again we have good quality at an affordable price. The rail is mounted on the receiver with three screws making the thing rock solid. It’s shaped to match the receiver round side making it more difficult to fit it incorrectly i.e. not parallel to the bore. The rail is offset to allow the use of stripper clips and iron sights. The downside is that when carrying the rifle the scope bumps on your back or ribcage and the gun is a bit off balance. A Piccatinny rail would have been more versatile than the dovetail but, so far, it has worked OK for me. Something that I really would have preferred is for the rail to be a bit longer in order to have more mounting options for the perfect eye relief.

K31 - Rail from ejection port

Last part I took from Swiss Products is the recoil pad adapter. The butt of the K31 isn’t straight but slightly curved, so fitting a recoil pad would have required some modification. Considering that I appreciate a curvy butt as much as the next guy, but I didn’t think I was up to the job (and I don’t have the proper tools). Once the adapter was in place I added a large Hougue rubber butt plate that was resized to fit the stock.

I knew that finding a good yet affordable scope would have been the most difficult part of my project. It had been 10 years since last time I was in the market for a scope and I had no idea where to start. So I was relieved when Tim of the Military Arms Channel enthusiastically reviewed a couple Primary Arms products and I quickly decided to give them a try myself.

K31 - Top view

After getting most of the above parts I contacted Primary Arms to place my order. Imagine my disappointment when I found out they don’t ship internationally. Thank God the internet has the answer for almost everything. I started checking reviews, considering my alternatives and my final choice was for an Optisan Viper 10×44. It’s Chinese made (as are the Primary Arms scopes), but in my opinion it offers the best quality for the money in that price range. Most of all, it’s available worldwide.

Before giving more in depth commentary on the scope, I need to spend a bit more time with it. I will eventually write a dedicated review, but for now all I can say is that I’m happy so far. Obviously it doesn’t have the same optical clarity of a top notch European optic but the difference to me isn’t worth the $1800 or so one would cost me.

Another not so easy decision was what to do with the stock. Again destiny (in the form of issues in the international payment and shipping system) determined the choice for me. While Boyds’ makes very nice stocks, I couldn’t seem to process a foreign payment for one, meaning a custom stock was out. So having the barrel threaded, the scope mount attached and a scope on its way, I decided to spend my time customizing the original stock rather than on the phone arguing with my bank or Boyds’ customer service. I ended up cutting the hand guard shorter, adding three ventilation holes on each side, adding the butt plate and adapter, remove as much material as needed for a floating barrel, adding a bit of McNett Camo Form where needed…et voilà!

Before I knew it, I was zeroing my scope in a 300 meter training range in central Switzerland that’s entirely build inside a mountain (link just in German).

Other mods I would like to add: Mojo peep sights, a bipod, extra/modified magazines (eventually stripper clips from Swiss Bianco). Considering that I went for a fixed 10X scope, the Mojo sights would allow me to engage close-range or moving targets quicker than using the scope or the current fixed sights. I haven’t Mojos’ yet because on this side of the Atlantic they retail for almost the same price as my scope. Depending on what the intended use of the gun is, in general, I would suggest you to consider the Mojos’ for your system.

For some reason, extra magazines for a K31 retail for about one third of the price I paid for the rifle. I will eventually buy a couple of them anyway or maybe buy an entire rifle to cannibalize on spare parts. Apparently there are modified 10/12 rounders (two magazines welded together or modified FASS 57 magazines), but I can’t seem to find a maker (if you are one, please insert your email address in the comments below). US-based Swiss Bianco published a video on newly manufactured stripper clips that I would like to have, but they are not available yet.

K31 - Target size

The result: the gun shoots like a laser. It is reliable, easy to operate and maintain, there is abundance of ammunition and spare parts, and it doesn’t look super tactical or in any way more lethal than it is. I think I successfully converted a 70-year-old battle rifle into a very good all around weapon keeping the overall costs below $600 (excluding gunsmith fees which will vary depending on where you are and what you can do on your own). Most of all, I had a lot of fun doing it. I’m planning to use it in sniping competitions that are becoming more and more popular here in Europe. Given the time, I’ll I’ll let you know how this old gentleman fares against competitors with equipment costing them ten times more than I’ve spent.


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  1. those rifles are neat. i don’t advocate modifying an old rifle but then again they really aren’t the same history rich guns like the mauser or enfield.

    Have you thought about making a cheek riser? I’m sure between the offset scope and stock comb you are doing a fair amount of turkey necking.

    also please tell us more about these “sniping” competitions? is it C&R type shooting or tactical rifle shooting?

    so what i’m saying is: good job and I enjoyed your article.

    • I was about to make a similar comment – looks like a stepladder to be able to see through the scope would be a useful accessory!

      Did you check under the buttplate to see if there was a slip of paper with the name of the person to which the rifle was originally issued? Many of them have that, and some folks have gone through the trouble of contacting the original service “owner”. Mine had the paper, but I didn’t track down the previous owner – sometimes there’s some interesting history there.

    • Sniping competition – You basically partecipate in team of two in some exercises one act as spotter. You have to engage different type of targets from 40 to 600 mt in random positions or even moving or reacting targets. Sometimes you have secondary weapon exercises.
      A famous one in Switzerland is the Gallinago Trophy but is open just on invite to non professionals, you can google it and you will find the information you need.

  2. I like my K31, even tough the wood furniture looks like it got marched on by a company of landser wearing hobnail boots. I installed a muzzle brake and a padded butt stock. The metal plate that came with the gun was bruising me up pretty good.

  3. I love my K31, it is the only C&R gun I didn’t sell in 2012 and for good reason. I missed out on the unissued K31s a few months ago. That was a steal for this quality rifle with the nicest trigger on a military gun.

  4. Nice gun.

    Steel buttplates are uncomfortable but they weren’t made for comfy shooting, rather bashing peoples face in. Wouldn’t recommend the muzzle brake.

    How are the laws in Switzerland regarding guns? Heard that people from specific countries (including mine) are disadvantaged in regards to getting permits. That and that full auto is legal. Can you confirm?

    • Swiss law – Yes full auto is legal if you have a collector license but asking around the ranges will not allow you to use the weapon (in full auto). Apparently there are military clubs in which you can use the full auto but they are open just few days a year and after invite (considering that I’m not Swiss nor military I guess I would never be allowed in).
      To buy gun you need to have a C level residence permit (meaning that you have been in the country a good few years) or like my case you are authorized to buy weapon in your country (I have an Italian, sporting gun license).
      If you are from a number of “risky” country like from few east european countries It’s a bit harder or maybe impossible without a a C level resident permit. So far I experienced Italian Irish and Swiss gun bureaucracy I would say that in Switzerland the law is the more gun friendly but in italy is not too bad as well.

    • A straight pull gun is easier to use left handed than a bolt action.

      Can’t you make some sort of bolt handle that goes over the receiver? Kinda hard to explain.

      • Someone does up in Montana. Don’t remember the name of the outfit. I’ll try to look in my notes and see if I can find the company and/or product.

        • Again, Swiss products to the rescue…with a left-handed operating rod. IMHO, looks beautifully engineered. There’s a Youtube video of installation, but not of shooting with it.

        • That is pretty much what I was thinking.

          But I have no need for it, I am ambidextrous. I just wanted to help out Jim R.

      • Left hand conversions are available. I’m right handed but shoot left handed and I prefer the bolt on the right hand side. More comfortable for me for whatever reason.

    • Left-hander here. If you can get the rifle on sand bags or a bipod, it’s actually not that bad. I use right hand to pull, but I shoot it as a left-hander. And there is an attachment you can buy that replaces the little knob, and runs over to the left side off the rifle. I haven’t tried it, but by some accounts it does the trick just fine. If I find that link I’ll bring it here.

    • I’m a lefty, and still LOVE THIS RIFLE. It’s flat out accurate. Never took it to a range but my first few shots of gp11 174 gr. Had me with in inches of a rock chuck (a rodent we have in montana)@ 400 m using iron sights. Plus when ejecting the brass it spins and whistles, just some “good fun factor”. Unfortunately Gp11 ammo is almost nonexistent anymore but I’ve heard the privi is good stuff.

  5. My K31 uses a scout scope, mounted forward of the action. I can use stripper clips and eject just fine. It required that I replace the rear sight block, which was much easier than I expected. I can shoot rat holes at 150 yards with it. The stock iron sights where good enough to hit a man, but not for groups.


    Magazines are so expensive because they were never meant to be interchangeable. They are serialized with the rifle, and were removable for cleaning.

  6. The K31 is an example of the level of quality that is possible in military arms when one actually cares about quality and equipping the troops with an excellent rifle instead of directing the business to the lowest bidder.

    Another set of examples are the Swedish Mauser-pattern rifles.

    Both use excellent steel metallurgy in their barrels and receivers, attention to detail, competent craftsmanship in construction, etc.

    • Given its intricate cammed bolt, I really don’t know if this is the rifle you would have wanted in the mud and filth of Guadalcanal, but up in the Alps and foothills, as an accurate battle implement, with the ‘every man a marksman’ Swiss militia (and the benefits of a nearby neutral financial center), taken together they were a good enough deterrent to deter Hilter’s hordes; not too many other countries successfully achieved deterrence from those guys.

  7. That’s it- I gotta get me one of those. Seen them on-line at a couple of places, Classic Arms and SOG- anyone bought from these guys? How are they to deal with, is there any other on-line dealers better? Don’t really like to buy that way but it’s the only place I’ve seen the K31s.

    • I got mine from Simpson Ltd, and was very satisfied with the whole deal. Their website has high-res graphics of each gun, and a good, understated description of condition, including measured muzzle condition. I looked through most of the ~400 K31s in their inventory (online) finding what looked to me to be a better-than-usual walnut stock and relatively low usage, and I was, to repeat, very pleased. When the rifle came, it turned out to be (per the tag) probably an officer’s gun, and in really nice condition. Taking the time to look at a lot of examples was well rewarded in my case.

  8. Bought a unissued k31 2year ago love it. Shoot it mostly with iron sights at 3 position comps the straight pull is quick. I out shoot scoped AR15 with it some days.. GP11 rounds can be hard to get but it can be reloaded also with prvi brass. I’ve a scope just mounted to it now for the hunting season so it a all year round rifle great for everything.. Love it.

  9. I recently purchased two K31 rifles, both had the typical beat up stock and fading metal finish but the second rifle I purchased from Calgary Shooting Centre has a near new condition bore & rifling. I refinished the wood & metal on the first one and kept the other original. These rifles are an absolute pleasure to shoot, very well made and extremely accurate. I installed the Swiss Products clamp-on muzzle brake & aluminium scope mount on one and I’m searching for a vintage scope to finish it off. I managed to find some reproduction chargers, unlike the waxed cardboard and tin originals these are polymer construction and cost $15 each. The muzzle brake reduced recoil to about 223 level and the scope mount is solid, it hasn’t moved after about 75 rounds. They’re definitely my favorite military rifles and will be see plenty of range time, at least until I burn through my stock of GP-11 ammo.

  10. This fellow mods mags. I want him to mod a 24 round Stg57 mag for me but I can’t find them for less than $100 us. If you know of any cheaper sources I will appreciate it.

    Rock solid industries is releasing a 10 rounder soon but I still want the 24.

    The conversion requires a K31 mag and an Stg mag. If you want , I will let you know how it turns out.


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