VDino-

I have a 6.5x53r rifle. It's light and handy, and the cartridge is easy to load.
I use Winchester .303british brass (tried others, the WW brass works best because of base-diameter) and a 6.5x54ms die set (because I already had the MS dies) with a shell holder for .303
For load recipes I look at 6.5x54ms data and work from there, I'm using the Hornady 160gr soft nose round nose (SNRN) bullets.

One thing to consider - you should do a quick look at this gun that you want, to make sure of the cartridge chamber.
There are other rimmed 6.5mm cartridges that it could have been built for, which might not be as elegant for use with available brass.
I once passed on a 16/6.5mm cape gun that was so very special in many ways (cartridge trap, peepsight in the tang, set trigger, pretty wood and engraving etc) but it was built around a long 'pencil-thin' cartridge for which I could not get proper brass or even a 'parent case' from which to form the brass.

If it is indeed a 6.5x53r chamber, grab it and love it!

Cheers
Tinker