I have the old NORMA 203 (NO the NORMA B203!).
It is similar to the IMR 4320 and the W N135.
Unfortunately for the Italian law we can not hold more than 5 kg of powder and this quantity also includes that contained inside the cartridges loaded!
Once the packs were very small: they were 100 or 250 grams at most. Now the packs are 500 or 1000 grams, and it is easy to exceed the legal quantity!
I also load cartridges for shotguns, so I also have powders for these cartridges!
For this reason I can not buy so many types of powder! Also if a type of powder is not good I spent my money unnecessarily! With the 100 gram packs it was easy to consume them quickly!
The Lee MOLD DC CTL312-160-2R seems to me suitable for the K-31 because the Shmidt-Rubin has a very short trhoat, and this bullet is the one that has the most tapered shape.
Or maybe I'm wrong?