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Posted: 9/14/2021 11:00:41 PM EDT
I usually post these in the Gunsmithing forum, but let’s see if It can survive in GD.
I made a friend at the range a few years back, chatted and swapped guns, had similar tastes in guns and shooting philosophy. Ran into him at an FFL, I was picking up a Parker Hale receiver, he was picking up two barreled K-31 receivers. He’s a bit of a K-31 nut, already had several originals. One thing led to another and I ended up borescoping his newly acquired toys. “this one was in the infantry, and this one was in the home guard!” So he decided to build the “good” barreled action into a sporter. He found a Richards Sporter stock, I pillar bedded and glass bedded it for him, and did the final innletting. He sanded and finished it. Link to Bedding Thread https://www.ar15.com/forums/general/What-s-Arfcom-Favorite-Bedding-Compound-UPDATE-Bedded-Rifle-Photos-/5-2407903/ ![]() ![]() ![]() It shot really good. ![]() But what to do with the other receiver with the crap barrel? ![]() |
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Love me some K-31. And I've got the strangest boner right now... Nice rifle!
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Since the factory guns shoot so well, we started wondering what one could do with a good barrel.
The idea of a K-31 based target rifle was born. So off to google he went to find someone to build one for him. He didn’t find anyone. Seems like maybe one or two people in the US had ever done it. We found photos of a gunsmith in New Hampshire holding one, but he never made contact with him. There was one you tube video of a guy rebarreling one, but he bored out the old barrel stub and screwed in a cheap blank and chambered it to a more common US cartridge. Not what my friend wanted to do. All the internet said NAY! Can’t be done. too complicated, with the cammed rotating straight pull bolt, the end of the barrel has a complicated ramp, extractor cuts, all has to be timed perfect, it’s 1.45 inches diameter, and metric threads. Looks like this. ![]() Gotta have a 4 axis CNC machine and someone to write the code! The internet said... |
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What to do with the old barrel and receiver?
Make one cheaply as possible and use as a truck gun or trainer for new shooters. Or just use the receiver and add a new barrel of a different caliber. Or open the bore up to fire a .308 win cartridge. Or a .338 caliber. 338x55 Swiss sounds pretty cool…. |
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So we went to see my buddy Russ, who owns an an R&D CNC shop. He makes neat stuff, prototype surgical tools, and things that go in space.
Sure said Russ, I can do it. For about a thousand bucks. Did I mention my friend is cheap ? He was discouraged, seemed like there was no way to get his dream rifle built. It’s all bullshit anyway I told him. This CAN be done on standard machine shop equipment, manually. The rifle was built in 1916. Manual machines. But it is the swiss watch of rifles, so it wasn’t going to be easy. So we went to see my neighbor, a retired, self taught machinist, who loves a challenge to play with in his backyard machine shop. ![]() The first step was to figure out if he coul even cut the metric threads. After a lot of research, he finally figured out a way to re-gear his Southbend 9 inch and cut the correct thread pitch. ![]() |
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Purchased four when I had the flow, but always wanted one in 7.62 NATO. Can be done, but is very expensive. I believe you can (or could back
In the day) send a rifle back to Switzerland and have the weapon rebarreled, (Hamerlli?) but it was very expensive even then. Issue GP11 is basically match grade ball, so I suppose there never was a big demand for the work to begin with. Fantastically accurate rifles. |
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My friend the K-31 nut was intrigued, so we pressed on. My neighbor spent his spare time for a few weeks tinkering with set ups, figuring out how to set up and make the cuts.
First he turned some dummy barrel stubs in aluminum to test the threads and see if he could reproduce the barrel thread pattern. ![]() |
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Having proved that he could make the thread pattern, my neighbor started trying to figure out how to reproduce the ramp and extractor cuts. This is what he came up with.
![]() The ring is scribed with the witness mark, and cuts, start and finish of the ramp, like so. ![]() Then placed on the new part ( after it’s been tourqued onto the receiver and stamped with a witness mark) Like so, and all the scribe marks transferred. ![]() |
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I don’t have many gun regrets but, I regret not getting a couple of those when they were cheap and plentiful not that long ago.
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Next the stub got set up in the mill, and the cuts made, and the ramp finished.
![]() ![]() ![]() |
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OST, OP you and me must be cut from the same cloth, I LOVE this kind of shit. Can’t wait to be retired!
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![]() ![]() ![]() So the next thing was to check functionality. The bolt went into battery and locked up on the new barrel stub. ![]() ![]() ![]() K-31 function test one |
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At this point, we had my friend the K-31 nut was convinced that my neighbor, the backyard machinist, could get the barrel fitted on his action.
The K-31 Target rifle dream was alive, so he ordered a 1.5” diameter, 28” , profiled to 1.25 at the muzzle, Krieger Stainless steel .308 barrel. We’re going all the way! K-31 Target Rifle! Stay tuned for updates! |
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I love this thread. What I had read was that rebarreling was something too complex to consider.
I have a K31 made in 1947. I had it scoped with an 4 power Unertl, but I found a 10 power leupold on GB, so that's what's going on it. |
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The K/G11 actions are much easier to rebarrel, the cam action and lugs are in the back of the receiver.
Never once have I seen a bad Swiss bore, except on Vetterli's. Curious how it was determined infantry versus home guard? Especially from just a barreled action. Out of the couple dozen K31's I have, only one scoped and I used the Graf's clamp on mount, left it all stock otherwise. I have 3 'u-fix-ems' that I got from AIM for $59. Mostly broken lumber and/or mismatched IIRC. I'm a machinist, might try something similar with one of my junkers. And kudos for using a horizontal mill, not often seen these days. |
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I got my K-31 for all of $85, back when they first came stateside. I got a St. Maries clamp on scope mount on sale, and mounted a cheap Bushnell scope to the rifle. I managed a 0.43" group of five at 100 yds or so, and that was with Prvi ammo, not GP-11.
Iraqvet8888 on YT got a target rifle made from a K-31: ![]() Custom K31 Sporter ![]() Custom K31 Sporter Other K-31 vids he did: https://www.youtube.com/results?search_query=iraqveteran8888+k31 |
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Quoted: The K/G11 actions are much easier to rebarrel, the cam action and lugs are in the back of the receiver. Never once have I seen a bad Swiss bore, except on Vetterli's. Curious how it was determined infantry versus home guard? Especially from just a barreled action. Out of the couple dozen K31's I have, only one scoped and I used the Graf's clamp on mount, left it all stock otherwise. I have 3 'u-fix-ems' that I got from AIM for $59. Mostly broken lumber and/or mismatched IIRC. I'm a machinist, might try something similar with one of my junkers. And kudos for using a horizontal mill, not often seen these days. View Quote The line was a joke I made after bore scoping. He bought two barreled actions of unknown origin. One looked great, the other was pitted. eroded crap. Who knows how it got that way, could have happened here in the States. |
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I'll be surprised if the final product shoots any better than your "good" gun.
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This here is a good thread. This place was once full of stuff like this.
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Massive tag. You guys that can machine metal are amazing! Much respect.
I have two K-31s, paid $89 each back in the day. They are stunningly accurate with GP11 ammo. I can't wait to see what a purpose-built target model can do. You guys are doing God's work, drive on! |
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Quoted: I wish I had gotten one as well....... damn accurate rifle View Quote View All Quotes View All Quotes |
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Quoted: The line was a joke I made after not scoping. He bought two barreled actions of unknown origin. One looked great, the other was pitted. eroded crap. Who knows how it got that way, could have happened here in the States. View Quote View All Quotes View All Quotes Quoted: Quoted: The K/G11 actions are much easier to rebarrel, the cam action and lugs are in the back of the receiver. Never once have I seen a bad Swiss bore, except on Vetterli's. Curious how it was determined infantry versus home guard? Especially from just a barreled action. Out of the couple dozen K31's I have, only one scoped and I used the Graf's clamp on mount, left it all stock otherwise. I have 3 'u-fix-ems' that I got from AIM for $59. Mostly broken lumber and/or mismatched IIRC. I'm a machinist, might try something similar with one of my junkers. And kudos for using a horizontal mill, not often seen these days. The line was a joke I made after not scoping. He bought two barreled actions of unknown origin. One looked great, the other was pitted. eroded crap. Who knows how it got that way, could have happened here in the States. I’ve seen a few pitted K31 barrels—after the Stgw57 had been around a while the K31s had mostly become “corps materiel”, meaning they didn’t belong to anyone and no one was going to get fined for abusing them. Most of the beat up K31 stocks probably happened in the 1980s when they were being used as something heavy for recruits to carry around so they didn’t mess up their real rifles. After that they ended up in the official surplus stores for like 20 francs or something. |
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Quoted: Don't get no funny ideas ! https://www.thefirearmblog.com/blog/wp-content/uploads/2018/12/22121212-920x608.png https://www.thefirearmblog.com/blog/wp-content/uploads/2018/12/555555555-920x443.png Larry Racine was the gunsmith supplying re-barrel services. He is gone. He did say, the earlier Swiss rifles were no more difficult to re-barrel than a 30-30. Very nice work. View Quote ![]() |
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Simpson's Ltd. has barrel gauges, they score their bores ( fair to excellent ) with them.
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K31 barrels are widely available in Switzerland, but they’re 800 CHF, and there would be an importation fee to the US, so it rapidly becomes a cost-benefit analysis.
While there are collectors over there, for the most part the mindset is based on target shooting, so Swiss gunshops are frantically rebarreling and refinishing what we would consider to be collector guns. The only thing that helps with K31s is that most Swiss are uninterested in them, so they aren’t getting shot and rebarreled as much. |
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I've had several k31's. They all will hold the xring in high power matches. A 1954 Hammerelli gave me 2 gold medal scores at camp perry vintage rifle match's. Lack of windage adjustment is it's only weakness. But that doesn't matter if it's shooting sub x ring anyway. Offhand is always the problem. The only comparable vintage rifle I have is a Finnish M39. It will group better than the K31. Put the Garands sights on the K31 and you would have something.
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OP, any particular reason your friend didn't want to go the bbl stub route, & just screw in a .308 bbl into a bored out 7.5mm bbl stub? Seemingly would be a lot less work.
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So my friend knew he wanted to go with a top tier barrel, but he wanted to retain the original cartridge so we didn’t have to alter the bolt or magazine in any way.
7.55 bore barrels aren’t on anyone’s list here, and he was already shooting .308 bullets through his 7.55 barrel anyway, a common practice amongst those who reload the Swiss cartridge here in the US, as 7.55 bullets are uncommon. So the obvious solution was a .308 barrel. Best deal was a Krieger, so that’s what he ordered . ![]() |
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Now he needed a custom reamer to ream a 7.55 x 55/.308 cartridge to combine the Original Swiss case with the .308 bullet and barrel.
After many emails and phone calls, he went with a Mason reamer. He sent them factory cartridge’s, and dummies loaded with the bullet he is going to shoot, in the necked up case, seated to the best length for the magazine. Mason made the reamer to fit that cartridge, along with the gauges. ![]() |
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Join date, post count etc.
And wtf are you doing posting a gun thread in GD? Sudscribed. |
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Quoted: Now he needed a custom reamer to ream a 7.55 x 55/.308 cartridge to combine the Original Swiss case with the .308 bullet and barrel. After many emails and phone calls, he went with a Mason reamer. He sent them factory cartridge’s, and dummies loaded with the bullet he is going to shoot, in the necked up case, seated to the best length for the magazine. Mason made the reamer to fit that cartridge, along with the gauges. https://www.ar15.com/media/mediaFiles/195613/07651793-8F44-4DEB-A7A8-513719B2E279_jpe-2091807.JPG View Quote How much do reamers cost that you have made specifically for a project? |
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