7.5x55 for Swiss K-31 Loading

[Alk8944]

If any of you load/have loaded for the K-31 I would like to exchange PMs with you!

Before going farther let me preface this with the fact I have been loading for over 50 years for at least 50 different cartridges. I have shot, and loaded for competition for quite a few of these, including some bench-rest. I am not a rookie at this, so please don't talk down to me as though I were!

The issue/question I have concerns the Swiss K-31. Specified COL is listed as 3.050-.060", and the manuals that include this cartridge show this as COL for most Spitzer bullets. They also (Sierra and Hornady) are using the Model 11 rifle, which has somewhat different chamber dimensions. While I can load ammunition or my Model 96/11 as long as 3.155" the longest LOA in my K-31 I can use varies from 2.880 to 2.850" depending on specific bullet! I have a box of Prvi-Partizan ammunition that is loaded to 3.025" that works just fine in the K-31.

I don't know anyone in my area that has or shoots a K-31. Is this typical of the K-31? Did the Swiss military ammunition have a sufficiently different ogive/nose length that allows their ammunition to be loaded to this length? What bullets have you successfully used for the K-31?

There used to be at least one Swiss Rifles shooting forum, but I cannot find it anymore. Is anyone aware if this still exists? URL?

 

[growr]

A dear friend of mine has several K-31's and always used the same load data as his .308 Winchester.....quite often it was a .308 147 FMJ or a 150 FMJ with IMR4895 powder. Seems like it was 44-45 grains, if you want I can call and ask to be sure.

As far as the overall length, you can't go very far wrong in using the Prvi-Partizan as a guide if it chambers properly and the tips of the bullets are not hitting the front of the magazine well.

The Swiss casing is slightly longer so the same loads for a .308 should have a lower pressure and still give you near the velocity you need without undue stress on the bolt. But then you knew that...

Seems like he seated the bullets to the crimp groove and they ran fine...maybe it will for you as well.

These are pretty cool rifles and I have always enjoyed shooting Clyde's K-31's in as issued military rifle matches.

Don't know if I have helped you any or not..........

Randy

 

[Ivan the Butcher]

The issue you are encountering revolves around the different bullets' ogive. The Sinclair International Bullet Comparator or the Hornady/ Stony Point Comparator will both work or you can make your own with a piece of bar stock ( drill a through hole the inner diameter of the lands, say .300", in the stock- a 1 inch nut will work! ) Slide the comparator over the functioning K-31 ammo and measure the total OAL, the set your seating stem to set the bullet you are loading to that depth. On most of my target ammo loading dies, I use the Redding Competition Seating Die which has a micrometer depth adjuster to facilitate this. It couldn't hurt to call Sierra and Hornady and see if they make a uncatalogued bullet with the correct ogive for K-31 ammo. Shooters all over the world use their products, so they may make one for the Euro market. Burger Bullets has several different ogives in 30 caliber to match needs of different shooting systems, maybe one of the higher numbered ogive will work in K-31 ammo.

About half of my target rifles like ammo touching the lands and the others prefer about 25/1000" set back or even more. Since you have ammo that the gun feeds to proper depth, I believe working from the land/ogive interface should give you a very accurate round. Ivan

 

[Alk8944]

Ivan,

Of course the ogive is the issue! That's why I prefaced the question with my experience.

I have already pretty well determined that the Berger or Hornady VLD bullets are what will work. The issue isn't LOA, it is seating depth and space taken by necessary deep-seating of most bullets because of the short nose of most bullets and the short throat of the K-31. I really wanted to know what others have done to avoid the deep-seating. I can't believe that everyone is using the various VLD type bullets at the price they all are! I can believe that most shooters are simply deep-seating and not giving any thought to how it affects pressures!

To achieve the 3.060" standard LOA for the cartridge requires a bullet that can be seated with a length out of the case of .880". .305" diameter seems to be the point at which bullets will contact the rifling hard. The nose length of 6 different Sierra, Speer and Hornady bullets checked have nose lengths ahead of the .305" point ranging from .650" to .695". The shortest of these require the respective bullets to be seated more than 1/4" deeper in the case than either Hornady or Hodgdon list for most bullets. But they are using the Model 11, which has a much longer throat than the K-31!

Even the Prvi bullet won't accomplish this, it is seated to 3.010". This bullet is a two-diameter bullet, which was suspected but verified by pulling one and measuring it! It measures .305" at the case mouth, and abruptly goes to .308" inside the case. It's nose is ca. .830 from where it becomes .305".

The Berger VLD Hunting bullets have a nose length approximately .894". The Hornady VLD has a nose of approximately 1.027". This is including carrying the ogive past the relatively large hollow point, so this is an "effective length". Either can be used at the full 3.060" LOA.

The problem is the Hornady is ca. $39/100 locally, and the Berger ca. $49! This is $10-20/100 more than most standard bullets. I hope you can understand why I was hoping for an alternative!!!

FWIW, while Prvi components are imported to the US, the two-diameter FMJ for the 7.5x55 Swiss is not among them! Yes, I had done my homework before asking if anyone had any other ideas. Thanks for an honest attempt at being helpful though!

 

[DWalt]

I have not experimented very much with the K-31 seating depth or bullet styles, but it does appear to have a little tighter chamber than the 1911's. Even full-length resized cases require a little extra push to close the bolt to the fully locked position. No such problem exists with the 1911 (Carbine or Rifle). I have quite a few Norma cases, but 7.5x55 cases can easily be re-formed from .284 Winchester brass. The rebated rim of the .284 creates no problems. After the first firing, I neck size only, and then chambering is OK in the K-31.

I generally use shorter and lighter .308 bullets, have even loaded quite a few GI FMJ bullets (.30-'06 and 7.62), and even some gas-checked cast bullets. I do not crimp. I have never attempted to optimize grouping performance, as the Swiss rifles are simply fun guns to me.

 

[Ivan the Butcher]

If the VLD's can work That half solves the bullet problem. I know of no one making bore riding bullets in 30 cal. I haven't figured out a die for re-striking normal bullets, That would be the best solution. I vaguely remember the Spanish/German CEMTE project using a long ogive bullet, but the public at the time just didn't understand (and probably still don't) what the advantages a VLD or at least LD ballistic bullet. It sounds like the Swiss beat the weight/length issue, by using bore riding bullets.

I just did a check of my library and see no new research for this cartridge. I tried to find good data from "The Old Days", before lawyers were the editors of reloading manuals, and found rehashed data mostly deleting obsolete powders and nothing for the powders that allow longer burn times without burning out a barrel.

I am sorry I can't give even a suggestion of a load with our bullets. Forum Member Swissman lives over there and may have a solution; you might give him a PM. I know he reloads for older military cartridges, but this round may still be a government subsidized, and they may not reload it! He talked of having to qualify with arms in this round and has family heirlooms he has used in competition. He may know of an online seller of the bullets you would need. He types English, but you may need translation software with the businesses. Best wishes, Ivan

 

[Nevada Ed]

A friend of mine has one and it is deadly accurate.

He shoots in a club and loads his for "Iron" target out to
400 meters but has a scope with his bad eyes.

Good luck.

 

[pakm]

reloading for the 7.5x55 swiss

I'm too cheap for buy special bullets. I had a large batch of pulled 147gr .308 bullets that I used. and your right, the original bullet had two steps I measured the front half at .302 and the rear half at .308.(I'm not a machinest, I'm a half fast tin smith). And yes, I found that the ogive? of the military bullet got in the way. I just seated the bullets a little deeper in the case. and they worked fine and where pretty accurate. with iron sights my old eyes throught they where pretty accurate. I started shoot lead bullets and the lead bullets had the two step dia. so they worked just fine as the length of the mag. would let them. And someone was right, the 7.5x55 is just a slighter bigger, fatter .308 round. but I'm getting too old to shoot the big guns any more. My shoulders don't like it at all.

 

[Dashriprock]

There used to be at least one Swiss Rifles shooting forum, but I cannot find it anymore. Is anyone aware if this still exists? URL?

This one?

The Swiss Rifles Message Board Forums

 

[Alk8944]

This one?

The Swiss Rifles Message Board Forums

No, found that one. There used to be a forum that dealt with target shooting and much historical information about the rifles. Some of this is available on other sites now, but not nearly what there was 10+ YEARS AGO.

Thanks for trying though.