This is from a friend of mine south of the border. He emailed this to me in response to a question I recieved from someone. Please note that all targets were shot prone with a sling. He posted this on many of the Swiss Rifle Forums.
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Parts of an old post:
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Parts of an old post:
The K31 can be a bit of a challenge because of the throat, or lack of it. My first efforts centered around the Lyman/Ideal 311291U. The "U" means "undersize". Since a lot of shooters thought it was beneficial to shoot bullets unsized, or sized very little, Lyman would continue to use a worn (undersized) but resharpened cherry to cut moulds and mark them "U". Usually this meant that the driving bands were closer to .309 than the .312 or so of moulds with a "new" (unworn) cherry. Unfortunately, it meant that the nose portion of the bullet would also be under sized, sometimes as small as .296. That was disastrous for most US .30 caliber rifles, but it works out well for the typical Swiss. The target below was fired with my first K31, which had by this time fired a few thousand rounds of jacketed bullet loads, so it had/has a "throat" of sorts, and I had no issues getting the old Lyman bullet to "fit". The groove diameter on this one is .307." The dispersion is 1-7/8", and as you can see it is almost all vertical. Heavier charges of slower powders, leaving less air space, may help.
The most reliable bullet I have found for the K31 is the Lee C312-1552R, which was designed by Ed Harris for the 7.62 x 39. On the surface, it seemed like an unlikely choice, but just seating some in dummy cartridges to check fit showed that it could be chambered in any of my K31's without intruding into the powder space. This is typical performance:
Extreme spread is just a skosh over 1-1/2". I have since found that bullets sized to .310 in this rifle with 16 grains of 2400 shoots just a little better, and it continues to shoot like this, day in and day out. Believe it or not, the groove diameter of this rifle is .3092".
This a 100 yard "Garand Match" target fired with this rifle and load. There are 34 shots in this target, 4 sighters (marked), ten shots standing slow fire (10 minutes) ten shots prone rapid fire (70 seconds); and ten shots prone slow fire (ten minutes).
These are all fairly mild loads and may not hold together well for 200 yards. I have done limited cast bullet shooting with the K31 past 100 yards because getting a heavier bullet to fit is problematic. If you can find a Lee 180 or 200 grain.30 cal mould that actually makes good bullets, you might try those. The 200 grain bullet with 16 grains of 2400 works beautifully in my 1911's. The bore-rider part of the Lee .30 cal moulds is undersized (.298-.299) to be of any use for our .30 cartridges, but works for the 7.5 x 55. The trick is to find a Lee mould that will cast good bullets reliably. I also have two copies of the Lyman-Ideal 311334, like the 311332, only 195 grains or so. The bore rider portion on both is .298, so the fit in my K31's is good. To get velocities higher than what I am getting with #2400 powder (1400-1500 fps), I will go with a medium burn rate powder like ReLoader No. 7. This has given me excellent results in the .308 Match Rifle, with the Lee 309160 round nose cast in linotype (10-shot MOA groups at 100 yards.) The same load (24 grains of ReLoader 7, Lee 209160 cast in lino) has given 1-1/2" groups at 100 in 7.5 K31 No. 831979. Have only tried one load with the 311334, and it was only so-so, but I was not having a good day.
Summary:
For 100 yards, the light loads with 2400 powder discussed above have been reliable and accurate, and have won a few 100 yard "vintage" matches for me.
For 200 yards, 180 grain bullet minimum, 1600-1800 fps. Charges of 24-26 grains Reloader No. 7 look promising. (that powder also meters very nicely through my old RCBS Uniflow) Bullets may need to be harder than plain wheel weights. Lino or heat-treating might be necessary for consistency
Hope this helps.
Resp'y,
Bob S.
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