GP100 Crane Latch Screw Thread Pitch?

[CvlEngineer]

My dad gave me his old GP100 service revolver (he was a local deputy sheriff for 30+ years) a while back and said it needed a little work. This pistol and another Colt SAA replica (well-made Italian job) were the only guns that survived in useable condition when my folks place burned down in a brush fire. Although the revolver did not suffer heat damage to its cylinder or frame and still looks serviceable, it did get hot enough to mess up some of the springs, including the crane latch spring. As I was rebuilding it and replacing all of the soft parts, I discovered that the crane latch screw is completely seized and will not budge for anything. Not sure if this is related to the fire or something else, but either way, it needs to come out. Since the spring is shot and does not securely latch the cylinder, it looks like I will have to drill the screw and re-thread the hole to replace the spring/screw. Does anyone know the size and pitch of the crane latch screw? I am hoping that once I drill the existing screw I can just use a tap to chase the existing threads because otherwise I will have to find someone who can fabricate a larger crane latch screw (it is a rather unique screw) and make the hole on the crane latch larger. I purchased a new crane latch and screw, but I don't have a scale small enough to measure the superfine thread pitch on the screw. I don't want to mess it up by using the wrong tap. Sorry I don't have any pictures to post because I am at work (and I typically don't take non-functioning firearms to work with me). Thanks to anyone who can help.

By the way, it is a .357 if that is important.

 

[NikA]

If the gun got hot enough to destroy the temper of the springs, I question whether the heat treat of the other steel parts wasn't affected.

I should be able to measure a screw for you later tonight if someone else doesn't get to it first.

 

[CvlEngineer]

If the gun got hot enough to destroy the temper of the springs, I question whether the heat treat of the other steel parts wasn't affected.

I should be able to measure a screw for you later tonight if someone else doesn't get to it first.

Thank you very much. I thought so too, but I went through it with a fine-tooth comb and it seems fine except for the crane latch issue (and melted rubber grips). Obviously, I am going to make sure to test it well before I hold it while I shoot it. I can send pics later. I would think that since it is a shiny nickel finish, it would have discolored if it got much too hot. It is possible that the spring was screwed up long before the fire because my dad hadn't used it for years. All of his other guns were totally destroyed, which was heartbreaking. He had some really REALLY nice stuff (Walther PPK .380, S&W .357s, .45 Auto Commander with left-handed safety, Winchester 10-guage lever action (I think it was a '73?), more rifles than I can remember, etc.). The two firearms that survived were in a separate display case that got protected when a stucco wall fell on it and insulated these guns and some of his most valuable badges from the fire. It was weird how there was total destruction except for the one corner where that case was.

 

[NikA]

Thread size appears to be #5-44TPI. Mine was a bear to get out because it was slightly bent, I believe others have said the screw is typically staked or thread-locked.