View Full Version : K31 Swiss ammo from 284Win Brass + 308 bullets?

09-23-2009, 7:47 PM
I saw this on another forum, has anyone tried anything similar?

Absolutely. That's the only ammo my K-31 has ever eaten. Just run the .284Win brass through the K-31 resizer die. Be sure your lube is good. Check the length of the brass and trim if necessary. (I haven't had to.) Load it up with .308 bullets. I get fine results with 150gr. Sierras or Speers, but the original GP-11 ammo uses 175gr. projectiles. I have heard good results from the 175 Sierra GameKing, which apparently has a profile similar to the GP-11 bullet.

I took my first hog with my K-31.

My favorite load is 43gr. of H335 under a 150gr Sierra lit by a CCI 250 primer.

09-23-2009, 9:40 PM
Lots of people have, because there was no good supply of 7.5x55 Swiss brass. You can get that now from Graf & Sons. Privi brass, it's very good quality and it's cheaper than 284 Win brass.


284 Win brass $586/1000

09-23-2009, 9:49 PM
In the past, the K31 rifles were available but no reloadable brass (GP11 is Berdan primed). 284Win cases (except for rebated rim) are very close to 7.5x55 cases. One pass through a resizing die produces useable cases. The rebated rim generally did not cause any problems as long as you did not load too hot (sticking cases).

When inexpensive Boxer primed 7.5x55 cases became available there was less need to reform .284Win cases. The K31 barrel has a nominal groove diameter of about .307-.3075" which is perfect for our .308" bullets.

09-23-2009, 10:02 PM
I use .284 brass because it is stouter than 7.5 brass. The case wall is thicker so you have to reduce the normal 7.5 load by a grain or two. I use either 4320 or 4064 and USGI pulled M72 match bullets.

09-24-2009, 5:20 PM
a little bit of work, but worth it.

09-24-2009, 5:52 PM
Back before I sold my K31s, I originally made handloads from Winchester .284 brass because Grafs was sold out of their 7.5x55 brass.

The only real significant difference is that the rim on .284 is slightly smaller than 7.5x55 rims. If you soft stroke, the brass sometimes won't kick out because the extractor loses grip on the rim and it just sort of stays in the receiver (above the magazine).

Not a big deal.

But get 7.5x55 Grafs brass because it should be cheaper than Winchester .284, and is most likely easier to come by since Winchester .284 is still a seasonal run item (last time I checked). Winchester .284 is often bought up by all the 6.5x284 shooters.

As far as 30cal bullets, yes, 7.5x55 uses .308" diameter bullets. The ***IMPORTANT*** thing to understand is that you will ***NEED*** to verify the correct seating depth to the lands for your bullets in your chamber. The COL data in reloading manuals will be worthless for the most part. The K31 was designed for the bullet used in Swiss GP11 ammo. That bullet has a VLD style ogive so seating a standard bullet with a long bearing surface will hit the lands a lot earlier than you would expect compared to the GP11 cartridge. So if you used, say a 168gr Sierra Matchking, the best thing to do would be to oversize the neck on a cartridge (or cut a vertical incision on the neck for slack) and soft seat the bullet into the rifle (put the bullet in the case somewhat high; chamber it in the gun, close the bolt, extract, measure base to ogive length or base to tip, seat shorter than that measurement for safety).

gun toting monkeyboy
09-24-2009, 5:53 PM
As the others have said, it works and people have been doing it for years. Welcome to C&Rs. Land of the improvised cases. That one is a simple 1-2 step conversion. I have seen (and done) cartridge conversions that had 7-8 steps start to finish. Back your loads down 10-15% to start with, and you will be fine.