The K-31 has a much shorter throat / leade than the previous G/K-11 and '96 models.

Thus, any cast bullet will have to be stepped down to .299" (ish), about .1500" forward of the neck, if you don't want them to "stick".

The fast-twist of the rifling will also limit the velocities somewhat, even if you cast in a "hard' alloy and use a gas-check.

Similar problems are encountered with the .303 cartridge, but there, at least, the throat is a bit longer as it had to accommodate the old Mk6 "torpedoes" LONG after they had ceased to be "front-line" ammo. The barrels continued to be made with this long throat way past the demise of Mk6, for the simple reason that ALL of the firing tables and sight graduations for Mk7 had been developed in the "transition" period and it was probably not "convenient" to fool around with them, again.

Swissicon K-31 barrels have such a short throat that you cannot use Sierra Matchkings, with their tangent ogive in them, whilst these will work fine in the older K-11s. Find a bullet that has a SECANT ogive for use in the K-31
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