7.5X55 Swiss ammo question

[gunauthor]

I have a new (to me) K31 Swiss rifle in 7.5X55 caliber. Yesterday I shot a box of factory loads, so I already have some fire formed brass. I also purchased a bag of 100 pieces of brass from Graf. Should I load this new brass to approximate factory loads and then just neck size when it comes time to reload? Or can I just start loading (16 grains of 2400 with a 170 grain cast boolit)? Thank any and all for your kind assistance.

[Maven]

"Or can I just start loading (16 grains of 2400 with a 170 grain cast boolit)?"

Assuming you had no problems with pressure or your K-31, I'd partially FL resize that brass and start with 15gr. 2400 with a CB between 170gr. - 195gr. By partially FL resizing, you back the die out enough so that the resized neck has a slight collar where it meets the case shoulder. (This helps center the loaded round in the bore.) If you can't easily close the bolt on such a cartridge, you'll need to turn the die down incrementally until you can. Btw, I sized my CB's to .309" for the 2 K-31's I used to own. Although accurate, the thin front sight blade was difficult for me to see, making precise aiming problematic.

[Scharfschuetze]

Believe it or not, I usually don't resize my 7.5 Swiss ammo until they get too sticky to chamber after several loads. I guess it'll depend on how much pressure your loads develop. The K31 doesn't have the camming power of a Kar 98 or similar bolt rifle.

I size my boolits for it at .311" and with my K31's chamber's tight neck, there doesn't seem to be enough room for it to expand much. While yours will probably be different, I just deprime, prime, slightly bell the case mouth slightly, charge and then seat my boolits. I might note though that you'll need a boolit with a fairly small diameter nose as there isn't much throat in the K31. NOE makes a good boolit for such use. I use the Privi Partisan brass by default.

I really enjoy shooting mine although I'd someday like to own one of the longer barreled versions that preceded the K31.