You are probably right that it could be shortened and maybe made a little fatter and still maintain the same ballistics. I know the .308 was shortened in order that it work better in automatic actions. On the other hand, the 30-06 was really long and I have never heard any complaints about the BAR and Browning's other machine guns not functioning well.
The 6.5X55 is already fairly short. There really does seem to be something remarkable about the .264 diameter bullets. The Swedish round is just about the right power to go along with it. BTW the old military round nose 160 grain bullets which are very long will penetrate better than anything I have ever seen. When I was about 18, I ordered one of those Swedes through the mail I also ordered some military ammo. I then went down to my Uncle's swamp and literally could not find a tree thick enough to stop one of those bullets.
I have shot a fair amount of deer and those 139 grain plastic tips kill them like lightening.
For some reason the Swedish Mausers tend to be more accurate than other similar rifles. I have no idea why but they really are accurate. In fact I have never had an inaccurate Swede and I once ordered six at one time. I am certain that I have owned more than 20 of them and not a bad one in the bunch.
Making it shorter and fatter like the .308 could also make it more accurate. I'm no ballistic genius but I know that the .308 is a more accurate round than the 30.06 because the shorter case allows more even burning of the powder. In fact the CMP won't allow .308 rebarrelled Garands shoot in their Garand matches because of the advantage (albeit slight) of the .308 over the '06. Don't forget that the powders today allow much more flexibility than what was available in the 1940's. Of course I'm pretty sure you already know all of this, so I'm just writing for other people's info. I sure am jealous of you having owned all of those Swedes, I've never owned one but I've drooled over pictures of them while reading articles and posts from owners. Maybe someday when I'm done buying match gear... (haha, like that will ever happen)
good shooting
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