I have used Federal with 150 and 180 grain spitzers and Remington Express with 180gr. CoreLokts and they have all done just what they should. I am sure the Winchester factory ammo will be just as good. Start with a box of whichever of those you best like the sound of and try it out. If the accuracy isn't satisfactory the others in turn until you are happy. Get into to reloading if you are going to shoot .303British a lot, it will bring the cost down significantly and you can work up a load that your rifle really likes.