Unfortunately I found that most sets you buy, only a few of them fit the sizes I need. What I do is buy cheap 4"-6" chrome shank Valadium steel screwdrivers and grind them to fit my screws usuing a dial vernier to get the tip correct for the slot in the screw. Most of the time you have to de-mangnatize the screwdriver after grinding them.
I grind them by using the side of the wheel, so that I can keep them parallel to each other.*
Most screwdrivers you buy even if they fit are not right for gun screws. Most screwdriver tips are wedge shaped so only a fraction of the tip is grabbing the slot.
*you should never use the side of the wheel for grinding, but I do it lightly and it is only removing a little metal.
