The threaded cap type wouldn't be 5x anything; the OP must be referring to the old type crane lock screw (the two-piece type).
FWIW, I get 42tpi on a Police positive, but with so few threads it is hard to be sure. A problem with gun screws is that gun companies like Colt, S&W, Winchester and Remington were around before there were any standards, and they made their own screws to their own specifications for the intended use.
BTW, note that that screw has a double head, so unscrewing it lifts the crane lock also. An ordinary screw will be OK to hold the crane lock in place, but without the double head screw, the lock will have to be pried out once the screw is removed.
Jim