Can anyone enlighten me why the vihtavouri powder manual lists loads for 7.5 x 55 Swiss as "GP31".

Obvious undocumented answer: They got confused between GP11 and K31. (The data are reasonably conservative and will be fine for any normal 7.5x55 Swiss rifle in sound condition if the usual prudent handloading practices are followed.)

 

I have seen GP31 used before, and I thought is was in the JGS website, but if it was, it's been changed.

JGS Precision Tool offers reamers and gauges for "7.5x55 GP-11" and "7.5x55 Swiss". What's the difference? We know that the chambers in the K31 and the 1911 series rifles and carbines are different, so my undocumanted guess is that one is for the "K31-type" chamber, and the other is for "everything else". But which is which ... ? Might be worth a phone call just find out.

Resp'y,
Bob S.

 

they could be referring to the 7.5 round for the model 1889 rifles as 7.5 swiss. It is 7.5 X 53.5 or somewhere thereabouts rather than the GP 11 7.5 X 55. There is a difference in the chambers as well as the ammo.

Frank

 

In German:
http://www.lima-wiederladetechnik.de/Patronen/7,5x55-Schweiz.htm

In Googlized Hinglish:
http://translate.google.com/transla...ima-wiederladetechnik.de/Patronen/7,5x55-Schweiz.htm&sl=de&tl=en&hl=en&ie=UTF-8

 

CIP standards sheet

This CIP standards sheet, titled 7.5x55, GP31 may be the answer to your question. Whether it's a typo that got carried over to V's production or is really the latest (1984) CIP standard is debatable.