Given the amount of obsolete load data some of us have managed to amass I'm hoping someone here can help me, yet again (you guys have been great with all of my hair brained ideas). I recently bought a rifle (action type is not important, but lets just say it has a 5 rd fixed box cartridge carrier mounted directly below the action and a little lever thingy that sticks straight off the side you use to load and cock it). it is currently in pretty good shape metalwork wise, other than the bore is shot out.  I know I got all of the cosmoline out, so that's not the issue, it's just dark and won,t print a group on a pie plate at 50yds.  I have a 1:9" barrel blank here so the plan is to rebarrel it after work one night. The rifle is currently chambered in 7.62x54R (if you haven't figured out by now it's one of the $85 Mosin Nagant Carbines currently flooding the market). I have been told the 6.5x53R, 6.5x54R, .256 Mannlicher, and 6.5 Vorstok (or something like that, i dont speak russian, sorry) are all the same cartridge. Does anyone know about this? I have also been told they're very common chamberings for European stalking rifles (hence why I turned here). i can't find load data for any of them anywhere, does anyone have any?  Any and all help will be greatly appreciated.

Have you checked out the Cast Bullet Association website yet?  I think you'll get more response there.  They do a LOT with those old military rifles.     They even have organized matches for them I've been told.

There is some potential for significant consfusion here.
There are multiple cartridges for the same designation in one case. In another there are multiple designations for the same cartridge.

There is a Finnish wildcat called the 6.5X53R based on the big Rooski round. So it should be easy to figure out what it looks like in your head. I think there is even a CIP specification for it though I have never heard of ammo being offered for it.

Then there is the original 6.5X53R Dutch Mannlicher round. The base of this round is very similar to the rim and case head dimensions of the .303 Brit. 
This round has also been referred to as the 6.5 Roumanian, 6.5X54R and .256 Mannlicher. 

Now here is a kicker. It is often called a rimmed version of the 6.5 X54 Mannlicher. The two are close but have other differences besides the rim.

What you want is the Finn 6.5X53R not the older original Mannlicher round.   
You might consider just cutting your losses on the Rooski rifle rather than have it lead you down the path to the land of no scope mounts or receiver sights.

[quote author=76777A7D796A6B617D6C180 link=1380072448/0#0 date=1380072448] 
I have been told the 6.5x53R, 6.5x54R, .256 Mannlicher, and 6.5 Vorstok (or something like that, i dont speak russian, sorry) are all the same cartridge. Does anyone know about this? I have also been told they're very common chamberings for European stalking rifles (hence why I turned here). i can't find load data for any of them anywhere, does anyone have any?  Any and all help will be greatly appreciated.

You can drop a .303 into your rifle and see if it feeds. 
The smaller body and rim maybe not even come close to working. 

Since there is not much documentation for the 6.5 based on the Russian case you can develop your own.
You can design a minimum size chamber and neck for long case life and better accuracy.  However you will also be out the cost of a reamer.

6.5x53R Mannlicher
* 160gr RN 32.0gr IMR3031
* 2100 fps
* reform from 303 British - trim rim to .526
* Case Lngth - 2.10
6.5x54R Mannlicher-Schoenauser
* 160gr RN 39.0gr IMR4831
* 2100 fps
* reform from 22 Swift - cut off rim & deepen extractor groove
* Case Lngth - 2.11

6.5x54R Mauser
* Buy them if you can - alot of reform work from 270 Win
* 120gr RN 36.0gr 4895
* 2500 fps
*Case Lngth - 2.125

.256 Mannlicher - No such caliber!

6.5 Vorstok - No such caliber even close to that name

Why you don't just buy a clean barrel for the Mosin Nagant is beyond me - but your choice.  The Nagant's with the right reload are accurate rifles.  Also presume you'll not desire to have it as a match rifle either 

Mosin Nagant - 7.62x54R Russian
* 165gr Spire - 46.2gr IMR4895 - 2600 fps

Found a listing for 6.3 x 53R Finnish in the 3rd edition of the VihtaVuori loading manual using 70,83 and 93 grain bullets with N140 powder at 2900 to 3000 fps. From the description sounds like this cartridge was used in re-barreled 7.62 x 53R M-N.

Pm sent