Let me tell you my recent story of woe.
Twice a year I go through my safe, oiling everything & recording the S/N's. I've been doing this for years now, so I have a solid procedure down, so it zips along somewhat smoothly. Still, it takes time to do 150-ish guns.
When I got to my Desert Eagle .357, it was gummed up something fierce due to my believing the hype about the lube's claims. (Made by a former SEAL, blah blah blah.) It took all I had to get the slide to move back out of battery, but it did. Slide comes off, barrel comes out, everything goes into the baking pan to soak in Hoppes. Scrub everything down until it sparkles (thanks USMC!), lube it this time with Lucas Synthetic Gun Lube. Slide, barrel & frame all mate nicely with no problems whatsoever.
Then..................................... I arrive at re-installing the firing pin asy.
For the record, I can detail strip a 1911 down to bare frame with no help at all. I can do a Beretta 92FS with some Youtube help now & then. (For the record, I refuse to do a USP, period.)
The Desert Eagle is really similar to a 1911 firing pin asy. Firing pin stop in a groove on the rear of the slide, a firing pin & a firing pin spring. There is a cut-out on the side of the firing pin to allow for the firing pin stop/safety to prevent it from moving, so it's obvious which way the firing pin goes in. Super easy, right?
I WORKED ON THAT BLANKETY BLANK BLANK BLANK BLANK SOB FOR OVER AN HOUR TRYING TO GET IT IN!!!!
After my blood pressure peaked around 300 over 299, I laid it all down on the table & went to the house to have a cold beer & think about my inadequacies on cleaning my own guns.
So............................ Next day arrives. I come home from work & go straight to the garage. I'm gonna fiz that SOB or I'm gonna dremel that SOB right in two! (I knew right then how Hacksaw Reynolds felt. You kids look him up.)
Initially, I had the same issue again: the firing pin would NOT go down in the firing pin channel. I visually checked it for an obstruction, it was perfectly clear. The spring was ok, no binding. THEN...............................................
I flipped the gun over & looked at the side of it. "Hmmmmmmmmmmmmm", I thought. "Was the safety on or off when I took the firing pin out? Well, shit, let's flip the GD thing off (or on, whichever it was) AND BY GOD IT SLID RIGHT IN LIKE BELONGED THERE!!!!!!!!!!!!!!
Ho Lee Schitt, I wasted I don't know how much time trying to figure this thing out & I simply stumbled onto the fix more or less by accident.
Yes indeedy, more beers were consumed that night in celebration. (After the guns were put away, of course.)