My dad gave me my grandfathers Czech Brno VZ24 that he brought back from WW2. I cleaned it all up and it is in beautiful shape. I thought all vz24's were chambered in 7.92x57 but I recently got some vintage ammo just to check the fit and the bullet won't chamber, this has never been modified (all numbers match-all) unless it was done during the war. What else could this be chambered in?"
It appears that the vz. 24 rifle was also chambered in 7x57 Mauser and 7.65x53mm Argentine. Of those two, I would bet it is a 7x57, the Argentines are probably pretty rare. The Israelies also rebarreled some to 7.62 NATO. The safest bet is to have a gunsmith make a cast of the chamber so it can be measured.
"Those who hammer their guns into plows will plow for those who do not."