K31 - Switzerland's answer to the Kar98K

[tac]

Raw linseed oil on walnut. Shellac on beech. Later, shellac was put on walnut then the shiny syn...

You are cerroct.

 

[Phantom Man]

You are cerroct.

I try to be rite when possible.

 

[Capn Jack]

Okay - nobody has asked for it, but some of you might find it interesting - THE SKINNY ON THE SWISS SERVICE CARTRIDGE - GP11 -

A look inside: GP-11 7.5x55 Swiss - Surplus Rifle Forum - www.surplusrifleforum.com

or, if you are feeling lazy - with grateful thanks to Surplus rifle Forum.

SURPLUS RIFLE FORUM - WWW.SURPLUSRIFLEFORUM.COM: FOR SHOOTERS AND COLLECTORS OF MILITARY FIREARMS WORLDWIDE

Originally posted by carteach0.

GP-11 Swiss 7.5mm, weighed in the balance.

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So many of the new K-31 owners share the same opinions regarding the Swiss GP-11
round. It always begins with: "Wow, this is incredibly accurate!", closely followed
by: "Where can I get some more of this?"

The 7.5 Swiss is an interesting cartridge. It has features that echo other notably
accurate and powerful rounds over the last century. Its case is shorter, stouter,
and quite tapered when compared to it's contemporaries. The sharp shoulder and
squat powder space reminds me of the 'Ackley Improved' series. P.O. Ackley thought
we could take most standard rounds and make the shoulder sharper and the powder
room a bit bigger, instantly improving performance. In almost every case it worked.
The 7.5x55 might have been built by Mister Ackley. It's every bit as powerful as
the 30-06, while also having the easy to find accuracy of the .308. In addition,
it functions smoothly with the unusual straight pull K-31 action.

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As usual, the measuring arsenal includes an RCBS 10-10 scale, Mitutoyo micrometers,
Central vernior calipers, some other assorted goodies, and a large cup of coffee.
Starbucks beans, ground at home, drip type coffee maker. A shlop of cream
in a big cup, and we are good to go.

GP-11 7.5x55mm is brass cased with a magnetic steel jacketed bullet. The bullet
core is solid lead with no voids, and seems very well bonded to the jacket.
Several bullets were sacrificed to the cutting wheel (monkey curiosity strikes again!).

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A feature of the GP-11 noticed by most people immediately is the unusual sealer
applied to the bullet/case junction. Unique in my experience, the Swiss painted
on a heavy band of wax. While it's not uniform by any means, the sample I looked
at had wax about .012"thick and .030" wide.

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This wax seal was easily removed with nothing more than a rough towel and a bit of pressure.
It's a soft wax, even 25+ years after it was applied. Once removed it revealed
a very heavy bullet crimp. Looking for all the world like a 'LEE factory crimp' its
a very firm and uniform crimping of the case into the bullet cannelure.
Many precision shooters swear by a crimp to encourage consistent powder burn.

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Two questions came popping into mind while looking at this wax...
(a) Where does it go when the rifle is fired? Is it perchance smeared down the case
walls, making extraction easier? If this is the case, why hasn't a problem with 7.5
handloads in the K-31 surfaced (tough extraction)?
(b) Could it be possible that this wax sealer serves to center the round in the
chamber? This might help account for the phenomenal accuracy of the cartridge.

It's time to look at some case dimensions.......................
In the run up to writing this, someone mentioned "It's going to be boring...."
Friends and neighbors, why would someone say this is going to be boring?
Because when we see the same thing every time, there's nothing interesting
going on. This ammunition saves everything interesting for the range, and
nothing for the load bench. It's so uniform that no time was wasted making
graphs. If the reader wants flat lines..... check out the average politicians
brain scan.

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The largest variation was found in overall loaded cartridge weight, mostly due
to the non-uniform wax sealer. Weight spread was 415.5 grains to 420.2 grains.
About 2.2 grains of that can be accounted for with case weight variations, and
another 0.5 grains in bullet variations. The rest seems to be the wax.

Over all length measurements were the most boring of all. It measured 3.045" Exactly.
No variation, *0*, Nada, Zilch, Sigh........

Case base diameter measured from .4941" to .4952", a .0009 variation. The horror
of it! Almost a thousandth of an inch! Those crazy drunken Swiss!

Case neck diameters ranged from .3360" to .3372", a variation of .0012" This
was of course measured after the wax was removed. The variation seems to be
due to the very firm crimp distorting the case slightly. Still minimal by military
ammunition standards, and certainly not bad at all by commercial standards.
There was almost zero variation found in neck diameter. They were round.

Case length began at 2.180" and ended at 2.184", a range of .004. This measurement
found no wild fliers, but was spread evenly across the range.

Tearing down the ten round sample, we find this:

View attachment 737271

The bullets pulled from the case with extreme force. The first one took four attempts,
till I realized a 'pull' was not going to do it, and a 'jerk' would be required. (Please
hold all jokes till the end of the article!). Even so, many bullets required two or three
attempts to get them out of the case. Not because they are glued in, but simply
that very heavy crimp set deep into the cannelure.

The powder appears quite fresh. It's an extruded grain not unlike IMR 4895, but with
a shorter grain. In grain size it looks like AA2015br powder, but has the same shiny
coating 'look' that IMR stick powders have.

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Powder charges weighed in from 49.9 grains all the way to a whopping 50.1 grains.
A 0.2 grain variation. You graph it, I'm going to take a nap.

Once pulled down, cases were weighed. They ranged from 193.2 grains to 195.5 grains.
This is a variation of 2.2 grains, and the largest spread of any single component.
The cases were mirror bright inside. Berdan primed, the twin flash holes were very
clear in the flat base inside the case. Looking at the pristine flat base inside the case,
a question came: How in the world did the Swiss form the anvil for the Berdan primer
while leaving the inside of the case flat?

Using the wildly dangerous torch trick to blow out the live primer (nothing too dangerous
in search of data for our readers!), an extremely uniform primer pocket was found.
In fact, the pocket appeared to be milled rather than punched. If so, this is incredible
precision and care for a military round. The flash holes also appear to be drilled
rather than punched. Stunning quality and meticulousness for a military round!

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The bullet, as stated, is a steel jacketed number with a lead core. Full metal jacket
with a strong boat tail. Weights ranged from 174.3 to 174.8 grains, a 0.5 grain spread.
Most notable were the diameter variations: Only .0004". The bullets measured from
.3076" to .3080", and were perfectly round. No variation at all in diameter was found.

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It would be an interesting day at the range, passing a few handfuls of this ammo across
a chronograph. By all reports, this is the most accurate standard military ammunition
built, and frequently wins matches. Perhaps that has something to do with the general
lament over the *lack* of GP-11. What supplies that do show up, vanish almost
instantly. In fact, if anyone has a case they'd like to contribute to the cause, I'll
happily continue testing it!

• Quote

Post by Rapidrob » Sun Nov 12, 2017 8:33 pm
Since the original posting of this article is long gone, the statement about the wax ring has an answer. The wax ring is vaporized when the cartridge is fired and coats the bore. This will do several things. It lubes the bore to help the steel jacketed bullet traverse the rifles bore with less friction. It keeps the powder fouling softer than a dry bore. This helps reduce corrosion. The grease aids in the cleaning the bore after firing. Since fired cases are dry to the touch once fired the wax may not help with extraction. It you shoot the cartridge with a piece of cardboard closely off to one side of the muzzle,there is wax on the cardboard.

On the old SRF we did an experiment mixing the wax and loading the case with a similar weight and type match bullet. A wax "ring" was made by using a heated wax mix and a small needle syringe. It did work, but unneeded due to our bullet jacket material. Plus there was so much surplus 7.5 GP11 ammo for sale at the time it was time consuming.

I know of no other ammo loaded for a military that is as consistent or of such a high quality as Swiss GP11.
I have not shot,nor know anyone who has shot the "new" made GP11 replacement ammo in 7.5 Swiss. [Edit - RUAG in Switzerland made a 'new run' of an estimated 26 miilion rounds of so-called New-GP11 in Fall of 2017. I have yet to hear that any has left Switzerland. RUAG UK denied its very existence, in spite of being shown a flyer from the Swiss factory trumpeting the production]

Tin Can Sailor
'Nam Vet
NRA Endowment Member
President New Mexico Military Surplus Rifle Pistol Shooters

@tac: Always informative, often humorous.

 

[tac]

The kindness of your comment only adds to weight my increasing modesty.

 

[CLT65]

Very informative, thanks guys. When I got my K31 about 20 years ago, the stock was OK except for the bottom couple inches of the buttstock. I spent a lot of time refinishing it to look nice. Since then, I've wished I had left it well enough alone.

 

[tac]

Should have looked for one from an MP unit, or transport rail or truck, even medic or FLAK - none of their soldiers wore crampons or had spiked heels and boot welts - the very things that inflicted the so-called 'beaver-chews' on your carbine.

 

[03A3Sporter]

" They still ARE milsurp. "

No, now they're expensive collectibles. They go from Milsurp to Expensive Collectible when the importation stops and there ain't no more where that came from.

They are still Milsurp, Edelweiss Arms is still importing them . FWIW they weren't all that cheap to begin with as far as the surplus rifles went. About $299 when I bought mine several years back compared to other guns which could be had for $50 to $99 . They are fine shooting rifles though that have few peers in the military surplus market.

 

[Aero Denezol]

I had a very nice 1950s K31 for a while that I sold because there was no ammo. I bought an Enfield No. 4 instead. Now the Swiss ammo is available and the Enfield ammo is sold out.

For all the professed love for the K31, I found they are surprisingly hard to sell. After a couple months, I ended up having to drop the price on mine. I shouldn't have let it go at all. That's probably the only deal in however many years of shooting/collecting I still feel pretty bad about. I ripped myself off.

 

[tac]

You can't find Prvi Partizan [PPU] .303 British ammunition? In America? I'm truly gobsmacked.

 

[Aero Denezol]

PPU Swiss was gone for a long time. Now it's back, along with GP11.

Last I checked PPU .303 was also sold out.

 

[03A3Sporter]

I had a very nice 1950s K31 for a while that I sold because there was no ammo. I bought an Enfield No. 4 instead. Now the Swiss ammo is available and the Enfield ammo is sold out.

For all the professed love for the K31, I found they are surprisingly hard to sell. After a couple months, I ended up having to drop the price on mine. I shouldn't have let it go at all. That's probably the only deal in however many years of shooting/collecting I still feel pretty bad about. I ripped myself off.

This is true, I have observed the same things many times . Most folks do not love or want manlicher or any other kind of straight pull actions. It is just not something Americans have embraced ever. People appreciate a very accurate rifle are the ones who tend to buy rifles like the Swede 96, M39 Finn Mosin and K31.

 

[Phantom Man]

PPU Swiss was gone for a long time. Now it's back, along with GP11.

Last I checked PPU .303 was also sold out.

Call PPU direct and ask them who has it. Contact info at bottom. Contact - PPU USA Ammo

 

[Phantom Man]

@tac I know this is a bit off topic but could you give us some of your pet .303 hand loads. Also curious if you used Vihtavouri in any?

 

[tac]

I don't have a .303 of any kind, remiss of me, I know. I never served with it, regardless of the comments about my great age and so on.

I DO use Vihtavuori N140 and N140 in both .308Win and 7.5x55 - two loads for each. And 6.5 Swede and 7mm Mauser, too.

Sorry I can't advise.

All I CAN advise from secondhand knowledge is to check the bore of any .303 you might have.

The USUAL bullet available is a 174gr .311 boat tail, but up to 600 yards or so they all seem to work better with a flat-base bullet if you can find any. Some older rifles might have bores of around .312 - 314...MUCH harder to find bullets in these diameters, even here in UK.

During WW2 No4 manufacture by both Long Branch and Savage, you'll find later models with two-groove rifling. Talking to pals in HBSA and LECA it doesn't seem to make any difference worth noting to the accuracy, but for goodness' sake don't go crazy mad about accuracy.

These rifles - ALL of them - were made as battle rifles, with the expectancy of a trained shot being able to hit a man-sized torso at 600 yards or so - somewhere, not the third button from the top down. In real life, very few actions took place at anything like this range - 50 - 200 yards being far more common. With that in mind, a three-inch ten shot group was accepted as average, and a two-inch group exceptional, so much so, that rifles showing this degree of accuracy were set aside by the tester to be sent to Holland & Holland for conversion to the No4[T] sniping rifle.

 

[Phantom Man]

I don't have a .303 of any kind, remiss of me, I know. I never served with it, regardless of the comments about my great age and so on.

I DO use Vihtavuori N140 and N140 in both .308Win and 7.5x55 - two loads for each. And 6.5 Swede and 7mm Mauser, too.

Sorry I can't advise.

All I CAN advise from secondhand knowledge is to check the bore of any .303 you might have.

The USUAL bullet available is a 174gr .311 boat tail, but up to 600 yards or so they all seem to work better with a flat-base bullet if you can find any. Some older rifles might have bores of around .312 - 314...MUCH harder to find bullets in these diameters, even here in UK.

During WW2 No4 manufacture by both Long Branch and Savage, you'll find later models with two-groove rifling. Talking to pals in HBSA and LECA it doesn't seem to make any difference worth noting to the accuracy, but for goodness' sake don't go crazy mad about accuracy.

These rifles - ALL of them - were made as battle rifles, with the expectancy of a trained shot being able to hit a man-sized torso at 600 yards or so - somewhere, not the third button from the top down. In real life, very few actions took place at anything like this range - 50 - 200 yards being far more common. With that in mind, a three-inch ten shot group was accepted as average, and a two-inch group exceptional, so much so, that rifles showing this degree of accuracy were set aside by the tester to be sent to Holland & Holland for conversion to the No4[T] sniping rifle.

That is a good response and I was not looking for a Percision load but just a common load as I have enough PPU brass now to start loading for it.
How about a 7mm load for a Spanish 1893?

 

[CLT65]

I don't know why I never bought any GP11 ammo back when it was cheap and plentiful. Instead I found some once-fires .284 Win brass and reformed it. I still have it and it works fine, but it's ironic that nowadays 7.5 Swiss brass is easier to find than .284 Winchester.

I did buy a whole bunch of HXP .303 British ammo a few years ago when it came in cheap. I like it a lot; shoots great, boxer primed and non-corrosive. I have so much I've thought about selling some of it, but then I wouldn't have it anymore!

 

[tac]

I don't have one of those either.

I can really only offer basic loading advice, with the usual provisos, on loads that I use in my own guns.

 

[tac]

I don't know why I never bought any GP11 ammo back when it was cheap and plentiful. Instead I found some once-fires .284 Win brass and reformed it. I still have it and it works fine, but it's ironic that nowadays 7.5 Swiss brass is easier to find than .284 Winchester.

I did buy a whole bunch of HXP .303 British ammo a few years ago when it came in cheap. I like it a lot; shoots great, boxer primed and non-corrosive. I have so much I've thought about selling some of it, but then I wouldn't have it anymore!

The Greek HXP .303 is generally thought of as some of the best ever made, and has not been seen here in UK for more than ten years or so. Enjoy it while you can - there is no more.

 

[Phantom Man]

I don't know why I never bought any GP11 ammo back when it was cheap and plentiful. Instead I found some once-fires .284 Win brass and reformed it. I still have it and it works fine, but it's ironic that nowadays 7.5 Swiss brass is easier to find than .284 Winchester.

I did buy a whole bunch of HXP .303 British ammo a few years ago when it came in cheap. I like it a lot; shoots great, boxer primed and non-corrosive. I have so much I've thought about selling some of it, but then I wouldn't have it anymore!

CLT,
If you do want to sell some of that HXP please let me know..

 

[CLT65]

These rifles - ALL of them - were made as battle rifles, with the expectancy of a trained shot being able to hit a man-sized torso at 600 yards or so - somewhere, not the third button from the top down. In real life, very few actions took place at anything like this range - 50 - 200 yards being far more common. With that in mind, a three-inch ten shot group was accepted as average, and a two-inch group exceptional, so much so, that rifles showing this degree of accuracy were set aside by the tester to be sent to Holland & Holland for conversion to the No4[T] sniping rifle.

I had a No.4[T] at one time, many years ago. I bought it cheap and had to research what that T meant. As I recall it would shoot around 2 to 2.5" groups at 100yards. I was disappointed because I thought "sniped" meant better than that. I ended up selling it cheap.

Before anyone gets excited, this poor rifle had been butchered before I got it. It was poorly "sporterized". The barrel was shortened, the forend cut, the front of the cheek piece rasped down where it contacted the stock, and it had a poorly fitted scope mount with an old "Hensoldt" scope on it.

Looking back, I'm sure the pieces of this poor abomination would have still been worth more than I sold it for, but this was back in the early '90s.

Added: even the receiver was trashed, because the butcher who "sporterized" it drilled and tapped the side of it for the scope mount they used.