Gents, I was looking at CoTW yesterday while on the can, and in the military cartridge section, I was looking at the pictures of the 6.5x54MS and the 6.5x55 Swede. I noticed that the MS had very little apparent case taper compared to the Swede, so I went to the pages that listed the case dimensions. There, I saw that the Swede had a rim/base diameter (in inches) of .480/.480, and a shoulder diameter of .424. I then looked at the 6.5 MS, and saw it had a rim/base diameter of .447/.450, with a shoulder diameter of .424. Thus, the MS and the Swede had the same shoulder diameter, but different rim/base diameter. I know the Swede is "sort of" from the Mauser family, so I looked at the dimensions of other cartridges in the military section to see if the MS shared the rim/base diameter of another cartridge. Guess what was closest? The 7.62x39 at .445/.447. Could it be that my 6.5 Grendel, which is a 6.5 PPC improved (and the PPC case is based off the 7.62x39), really be a shortened version of the the 6.5x54MS? Would that mean that Kalashnikov was exposed to the 6.5x54MS since it was a Greek military cartridge and began expirementing with it, and came up with his 7.62x39? Or is this just a coincidence?

And if this is in the wrong forum, Moderator feel free to move it...

Those rim/base dia dimensions are different in other books/blueprints. Co-inky-dink, I don't really know, but the 6.5x52 Carcano(7.35 Terni) is awfully close to the MS also.

Maybe so. The same edition of CoTW also says that the 6.5x52 MC may be formed from the 6.5x54 MS.

I think it is interesting to look at the dimensions of different cartidges from different countries and different times. If you look at the rim/base dimensions of the 350 Rigby Rimless Magnum and the 35 Newton, they are awfully close as well. The Rigby preceeded the Newton, so did Chas. Newton cut off the Rigby case and neck it down to get a 35 magnum to fit a 30-06 length action?