My K31 had a .297 bore and .307 groove, first tried RCBS and some Lyman molds, all of the ones I tried were too large for the bore, my friend made a nose sizing die for the 30-180-sp and 311299, sized the bore ride section to .297.
ordered a mold from Mountain molds that fit the rifle, using SAECO 301 as a guide for the shape, and it shot well, shot a postal from the other site with the 308329 (I think may have been 359) 180gr long pointed bullet.
bought the NOE mold made for the K31, and this shot consistently 1 1/2MOA, with 78yo eyes at the time, factory sights.
my friend had some Chinese powder BW-36, said 4895 burn rate, not really more like 3031, no flash supressor, used it up went to Benchmark at 32 grains, very good accuracy
I have about 200 bullets sized and lubed .309, if you want to try the bullet, free for the shipping...PM
mountain molds target 100yds, postal was at 50yds