Having both, their performance difference ( along with the 260 Rem) is pretty non existent..
My favorite cartridge of all is the 6.5 x 57..mainly because of its being more a rarity.. I also just neck up 257 Roberts brass..
the Swede, if you have a push feed, the rim diameter vary some between manufacturers...
I built my 6.5 x 57 on a long action, and it is throated to where I can seat bullets out to magazine length in the model 70 its on..
in that scenario, one can match 6.5/06 velocities...
the only difference is in the 6.5 /06, the bullet is occupying part of the powder capacity... on the 6.5 x 57, the bullet is not... but you end up with cartridges with the same OACL...
I think the 6.5 x 57 is more practical than the Swede as it can use Roberts and 7mm Mauser brass by just necking up or down as the case may be...
the Swede is more readily available, but has some variation in specs between various manufacturers..
Die costs are a concern also... the 6.5 x 57 is considered a custom... everyone makes the Swede dies..but dies are actually a low cost in the consideration of the life of a rifle..
only go with either if you are doing it on a long action..
if you are doing it on a short action, then I'd do a 260 Rem...
for the 6.5 x 57, as long as 6mm Rem, 257 Roberts and 7 mm Mauser brass are readily available, you never have to worry about brass availability...
Me, I just love having something different than all the other guys...and when you got what they don't know what it is, but they see how accurate it is...then they really want to know all the details and how to get one... then you just smile and be quiet...and let them drive themselves nuts..
( as a side story, some guys who I know that are always shooting the latest greatest and act all snobby with their wildcats... they saw me nailing some targets at 700 yds on our range one day...they wander over and ask me what caliber I am shooting..
since I have seen them act all high and mighty to other folks around there before, when they asked me what I was shooting, I told them I was shooting a Winchester 6mm Medium Length Short Mag..
of course, they admitted they had never heard of it...and asked was it a new cartridge? I told them I wasn't sure how long it was out, but there are rifles available for it...
so these guys leave, and I am sure are going home to either check it out on the Winchester web site, or stop by one of the local gun shops and ask about it..
as they left, my buddy was looking quizically, and asks what the hell is a Winchester 6mm Medium short Mag? I thought you were shooting a 243? My response was " I am, but those pompous bozos don't know that..."
