That all depends on bore dimensions and condition I reckon. It's been my experience that Finnish built Mosins and German made Argentine Mausers usually shoot just as well with .308'' bullets as they do with the 311/312's. The bores of Russian and Argentine made barrels can vary widely, groove diameters as large as .316'' have been reported in MN's and .314'' in Mausers made by the Argentines. Like WarPig I can't comment on the SVT's but doubt they'd be any more consistent.
As said above you have to look for 303/7.7mm to find them. Had a quick look on the Grafs, Midway and Natchez websites and they're all are showing a variety of 311/312 150gr bullets in stock.