Doable. As noted, you need to reduce the powder charge a bit. The last ones i made were pulling down with about 44gr powder per 7.62x54r, i loaded the 303 with a full scoop from my lee dipper that came with my classic loader in 303, which worked out to a bit under 39gr if I remember correctly.
As a comparison, 303 max loads with h335 is 42gr, with bl-c2 is 48gr, with max pressures at 42000 and 39000 cup respectively, while max x54r loads are 49.5 and 55.5, with pressures of both being about 46000 cup.