There are a number of ways to adjust screw timing, these are a few methods I use that do not need too much effort on my part and each in there own way perfectly cures the problem.
Simplest of all for countersunk and raised countersunk screws is to use a countersink bit turned by hand to remove just enough material from the countersink to time the screw correctly.
For domed head screws spin the screw in a drill chuck and use a file on the head's flat surface to remove enough material to get the timing correct. This takes time and by far the method I dislike but it works well.
The last method appeals to me for its simplicity and it works well each and every time, though I will say don't knock it until you have tried it.
This simple fix is not from the gun trade but that should not matter, all it consists of is some strands of wire wool wound on the screws shank just under its head. By removing or adding strands of wire wool you can get the tightness and timing perfectly, also once done it is a permanent fix and easily reversed with no tell tail signs it was ever done. Sneaky, fast, and appeals to my lazy streak!
