Basically what I'm saying is if your 303 is a 2 groove rifle it will most likely shoot the most accurately with FB bullets vs. the BT. If it's not a 2 groove shoot whatever you like,your rifle will tell you what it likes best.
Cordite powder burns much hotter and the BT bullet used made erosion much worse. Smokeless powders used today burn much cooler and will work fine with BT bullet. BT bullets gain the advantage at about 300 yds. and beyond over the FB bullets since most of my shooting is done well under 300 yds. I just use the FB bullets in all my mil-surplus rifles.