As parts become more scarce and more expensive, the simple screw deserves a few thoughtful moments. All of us have experienced a nice Lee Enfield with screwheads that are mangled, mis-shapen and somewhat buggered.
Because of the many different factories involved over many decades, slight variations in screw slot sizes can add a very difficult dimension to a screw that has been either in place for over seventy years or has already been rounded out by poorly fitting tapered screw drivers.
A tapered screw driver blade, if thick enough, will contact the top of the slot on both sides. But when you turn it, the taper tends to lift the blade out of the slot, losing its contact and ending up tearing the opposite outside corners out of the slot.
A hollow ground screwdriver, correctly fitted in a good screw head, contacts the inside walls of the slot evenly all the way to the bottom. It drives without wedging upwards and gives you by far the best chance of success.
I use this set of hollow ground screw drivers. It doesn’t mean I’ve never buggered a screw head, a close look will show a few broken blades in the set which probably damaged screw slots. If every screw you stuff costs $7-8 and you bugger them again next time…. makes the price of a decent set of screwdrivers very good value.