Reload away
Absolutely the K31 can be reloaded. I have several, been load testing, found for my rifles an excellent load with surplus WC852. Since my powder came from Jeff Bartlett at Gibrass.com and is different from the other lots of WC852 floating around, I am not going to quote a charge weight. However, 2700 was originally a different 98,000 pound lot of WC852, I think that 2700 would also make an excellent ball powder for use in the 7.5 X 55 Swiss.
You can use standard .308 bullets, you will have to seat the bullets deeper than the OAL of the Swiss ammo or the bullet will get jammed in the throat of the barrel.
I have some data. You can see that my AA4350 load is just under the service rifle velocity. I think any of the 4350’s would be an excellent choice for the 7.5 Swiss.
I purchased cheap Lee dies and they work fine.
I was unable to find any go/no-go case gages for the 7.5 Swiss. I used my Stoney point gages to set up my sizing die. My recolletion using the C375 stoney point gage, I set the headspace on my cases to 1.830”, this was based on measurements of fired cases.
Using "C 375" Stoney point gage
Headspace, Indep, Fired Measurement Average: 1.834
K31 Rifle
AP11 Swiss Ball headstamp DA 78
Ave Vel = 2565
Std Dev = 9
ES = 23
Low = 2551
High = 2574
N= 4
168 gr Nosler Match 51.0 gr AA4350 INDEP brass and primer OAL 2.850
22 Dec 01 T = 58 ° F
Ave Vel = 2536
Std Dev = 16
ES = 45
Low = 2510
High = 2555
N= 9