Originally Posted by GeorgiaRaised85

So, by removing the flag, that disables the lock from engaging itself under recoil?

Yes. The lug that actually locks the hammer is a little lump on the side of the "flag" itself. Remove the flag, you've removed the lug, and it cannot lock. That's all I've done, so far, to my 340PD lock.

If the spring for the fork were to fail, what could possibly happen?

The fork spring is a coil, compression spring. With the plug in place, the spring is almost fully compressed, with no place to go, best I can tell. If it collapsed and lost all spring tension (HIGHLY unlikely) in theory, the fork might be able to move forward enough to release the plug, but the spring is so close to going solid with the plug in place, I'm not sure it would release. If it did, at least in my 625, I think the result would be a plug that floated back and forth in the hole a little, but I don't think anything would hang up. If the fork itself could get loose, it might hang something up, but it doesn't look to me like it could get loose into the internals.

I don't suppose the spring could fail, but how long could that spring stay at the proper tension to keep the Plug in place? 10 years? 20 years? 30 years?

The "proper tension" of the spring is not going to be critical. One thing for certain, the likelihood of the plug or fork coming loose for any reason is a HELLUVA lot less than that of the flag locking up the gun. If anyone with a remotely mechanical bent looks closely at the unmodified internal lock, he marvels at why they don't self-lock more often than they do.