(Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7.62×45mm can handle up to 430.00 MPa (62,366 psi) Pmax piezo pressure.
regulated countries are currently (2014) proof tested at 537.50 MPa (77,958 psi) PE piezo pressure.
Re-barreling, or even "Sleeving" the barrel of the Czech Vz.52 carbine in order to shoot 6.5mm Grendel is a viable option that provides a common factory / boxer primed and reloadable compatible cartridge.
The .250 Savage would also be another reasonable option for rebarreling the Vz.52 rifle, if intending to use the OEM magazine attention to the Overall Length (OAL) of the finished cartridge will be important.
Boxer-primed cases can be easily formed via resizing and trimming 6.5×52mm Carcano brass, but these are difficult to obtain.
Another route is to use the .220 Swift cartridge, but along with resizing and trimming, this also requires turning the rims down on a lathe and cutting deeper extractor grooves.
.300 Savage is probably the closest in size for a relatively available American Boxer-primed reloadable .30 caliber cartridge.
A .300 Savage chamber reamer can open up the Vz.52 chamber to the correct .300 Savage cartridge case body dimensions with the deeper and wider shoulder; OAL would have to be adjusted to fit the magazine as well.
A reason to change the original calibre can be to comply with a minimal permitted calibre or bullet weight for the legal hunting of certain species of game or change external or terminal ballistic behavior.
It is low recoil and so can be used from carbines, but has long enough range to be used in machine guns and designated marksmen rifles.