All, The weather was just about perfect for a trip to the range today so after cleaning up the leaves & mowing my lawn for the last time this season, I drove out there. I shot the HFP match in the sitting position using my "as issued" K-31 and Lyman #311466 for one target and Lee C309180-R for the other. Both were sized to .309" and seated over 18.5gr. WC 820 + Win LR primers (no fillers). I was quite happy with the results considering that I rarely shoot from anything but a benchrest position.
Sitting position: It's not bad and I had hoped to sit with my back against one of the uprights (telephone pole segment) that supports the roof over our firing line, but I forgot about the sun: We shoot to the ~SW (can't be changed), which isn't good, since the low sun at this time of year is directly on your sights. My first targets were terrible because I couldn't see the rear sight because of the glare. However, there is a rifle rack (no back support though) that is completely shaded by the roof and enough space between 2 of our concrete benches to allow a clear shot at my 50yd. target. By using an old bath mat (bench cover) that I carry with me, I was able to sit on the rack comfortably and actually hit the target.
Btw, I had 17 rounds loaded with the Lee "soupcan" loaded with 15gr. WC 820, which I fired from the same position, but at a single target. The results were impressive! If you happen to have that mold and a K-31, by all means try the combination for it's a good one. I.e., it's one of the better CB's for the K-31.