the BM59 is a .308

you can get or used to be able to get ramline 10rd mags for the remington 7400/7600 series of pump and auto loading .06 rifles.
for your price range i'd buy a used garand those clips hold 8rds of .06
and they are very nice/accurate shooters. until i got out of .30 cal stuff i had a few .308 converted garands 3 full size and 2 tankers.