I highly doubt any die manufacturer's are going to change their seating and sizing dies over concerns about shooting 0.308 bullet through Swiss rifles. Those 308 diameter bullets shoot fine.
Undoubtedly pressures do increase with a larger diameter bullet, but so what, decrease your loads. Millions of 0.357 diameter bullets have been shot down 0.355" groove diameter Colt pistol barrels. I am going to claim, that the greatest source of danger, is if the case neck is pinched in the chamber. If the case neck is pinched, pressures go way up. I learned this decades ago when I assumed it was OK not to trim once fired rifle brass. Once fired brass has the most case neck growth, and the case necks on those reloads were in the throat. That caused blown primers.
I am not a fan of tight chambers and tight throats are OK if you know, and cut your loads accordingly. There are those who believe "tight" chambers, "tight" throats are a quality attribute, and want weapons chambered with reamers on the minimum side. These things just cause more problems later, feeding, extraction, not going into battery because ammunition is tight. If the case neck expands, and releases the bullet without pinching, a slightly larger bullet will not be an issue. Here is what to do. Take a fired case from the 7.5 Swiss and see if a 308 diameter bullet will drop in. If it does, you have plenty of clearance and all you have to do, is develop loads normally. I do not recommend hot loading old military actions, just keep them to service pressures and velocities.
AA4350 gave excellent accuracy and just about duplicates Ball velocities with 51.0 grains and a 168 Nosler Match bullet. As you can see 52.0 grains produced velocities over Ball, so I do not recommend that load. It is here for reference.
Instead of AA4350 I am shooting surplus WC852 in the 7.5 Swiss. This is a ball powder, and I purchased my lot from Jeff Barlett at GIBrass.com . It turns out Accurate Arms purchased a 90,000 pound lot of WC852, faster burning than Jeff’s lot, and now it is labeled as 2700. My lot of WC852 shoots extremely well, was dirt cheap, and I am using that up. But if I did not have the surplus powder, I would give IMR4350 or AA4350 a go as it shot very well.
7.5 x 55 Swiss Model K-31
AP11 Swiss Ball headstamp DA 78
24 Mar 04 T = 70 ° F
Ave Vel = 2565
Std Dev = 11
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 = 17
ES = 45
Low = 2510
High = 2555
N= 9
168 gr Nosler Match 52.0 gr AA4350 INDEP brass and primer OAL 2.850
22 Dec 01 T = 58 ° F
Ave Vel = 2624
Std Dev = 31
ES = 72
Low = 2588
High = 2660
N=5
en Garde!
Good morning I need some information. I have a ,Lee re-loading dies for the Swiss 7.5 x 55 K31 rifle ..the challenge is that this re-loading set has the seating die for the .308 " while the bullets of the GP-11 and the Perigrine bullets I have is .306" ..I do not want to shoot .308 " through the .306 " bore...please contact these companies and ask if they have a seating die with a .306 " diameter ???i
