There is an article on the 6,5x54 M. Sch. in the latest edition of Rifle, (Sept, 2011, No 258). It states that post-war Mannlicher's normally have .264" bores whereas "older" ones ranged from .266-269". Mine is a Model 1903, proofed in 1928. I slugged my barrel and here's the results:

.2564 .2565 .2564 across three different locations on the lands
.2681 .2680 .2678 “ grooves

I've since brought a box of Hornady .268" Carcano bullets which actually measure slightly less in diameter than .268". As suggested, I'll be using a light starting load and measuring base expansion compared with factory loads and also using a Chrony to judge pressures. This rifle does not develop expected velocities with the normal .264" bullet, though the Hornady accuracy is much better (2" or so @ 100 yards), than the RWS one which is undersize !

I had a Model 1950 Mannlicher and the chief difference between it and the latter M.1952 and other post-war guns was that it had no safety beyond the original bolt wing-safety. Later models had side safeties or sometimes tang safeties. Bullet shapes other than round nose will work in some early Mannlichers such as mine, a lot seems to depend on the individual rifle and it's feed ramp and perhaps also the magazine alignment. I've had good results with Nosler 140 grains, and even 129 grain Hornady spire-points. This in a long-throated carbine.