Have a gremlin I am chasing on my main carry pistol.
First the set up on this. Pistol has always been rock solid reliable and I have run well over a thousand rounds trouble free with her.
Had a range mishap a couple months back. Pistol was laying on the shooting table with the slide open and was accidentally knocked off. Landed muzzle first in a clay sandy mix here during a historic drought. When i picked the pistol up and looked down the barrel to see if it was plugged ( was in a BIG way with this stuff) this stuff fell through the barrel into the action.
Dropped the slide wipe out and blew out what I could but the pistol has not run right since. Ran about 10 rounds that day and it kept jamming so took her home. Dropped the slide and thoroughly cleaned it out with solvent and q tips but did not do a full on disassembly.
Brought her out Saturday to the range for the first time since then. Ran 50 or so rounds flawlessly out of the case so I set it down.
Came back later loaded her and she did not drop all the way into battery noticed the slide was sticking and hanging just before it was locking up. Bumped it into battery fired a round and it jammed. Removed the mag unloaded the pistol and it cycled smoothly, drop a round into the chamber mag in or out made no difference but it was sticking just before coming fully into battery so put her in the case. Keep in mind just did a spring job and the recoil spring has under 250 round on it. Also when I got home swapped in a fresh spring same issue.
Used spray Remington dry lube after that last clean so wonder if it just got hot and gummed up or something?
Pulled it down and cleaned her last night this time with spray blast then military CLP to get any gunk out then lubed it well with Break free and let it sit for an hour or so.
Seems back to normal for now but have not had it back out on the range and got it hot.
Anybody seen this and have suggestions here?

Never have encountered the described issue, and I've even got a 5943.

Then again, it's a rare to find a firearm muzzle down in anything.

Should your heavy duty latter spraying doesn't do the job (though it likely has) then a full teardown seems in the cards. Bluebelly2 has some really good third-generation, semi-auto teardown videos on YouTube (find 'em here: blubelly2
- YouTube).

Later.

Well this one is giving me fitts! With an empty mag everything seems fine, but load a full mag and the slide sticks just before full lock up. Been through it a couple times now but find nothing out other norm. It feels like it's dragging when you pull the slide back slightly and if you do it really slowly it will hang but only with a loaded mag (same issue with 4 different mags). All happened after the fall and before it was rock solid reliable but dang if I can find the problem so far!

Possibly did you get sand/dirt/rocks in the action then when you fired it, that foreign material gouged a burr into the slide or frame?

Run a dry Q-Tip all along the slide rails and frame rails and see if there's a burr that grabs the cotton.

I would begin to suspect something is amiss with the barrel where it's binding on the locking lugs or the barrel cam as it tries to lock into battery.

Since the gun landed muzzle first with the slide locked open, have you checked the condition of the cam surfaces on the barrel block/lug and the frame for a possible burr or deformation?

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Conrad
SWCA #1830 SWHF #222

Is it perhaps possible that also your mags are dirty and the cartridge release timing is not correct?
Since you state that without the mag the gun action is smooth....

Factory ammo or reloads?

I've had 9mm that don't like 124gr..

I would reommend a complete cleaning including removing your grips just in case as sometimes only a small amount of dirt will cause serious problems if its gets into the wrong place.

Did this and found a spot of grit deep in the slide rail of the pistol. appears that I may have not gotten all the grit out of the rail on the actual slide. Deep cleaned the rails with a toothpick and cloth and it feels better. Will know when I can get it to the range if this was all of it. At the least your tip definitely helped me find grit inside that rail I had missed so THANKS!.

Factory 115 grain. I had a mix of Winchester White Box , Blazer Brass and Remington on hand.

Mags all run perfectly in my 6904.

Have not pulled the grips so will do.

I'm not sure what you have done as far as cleaning is concerned. Perhaps a complete tear down and ultrasonic cleaning or washing would be in order. I would do the mags as well.

Keep in mind that the small particles of dirt/debris can embed themselves in the metal contact surfaces and cause problems, even when the contact points appear to be clean.

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Ret. LE, FA Instr, S&W Armorer

Forgot to post a resolution on this one guys.
It was that piece of sand or grit embedded deep in the aluminum frame rail. Must have happened when I blew it out and then shot it. Caught it by running a Qtip carefully down the frame rail. I then did a simple deep clean scrubbing of the frame with added emphasis on the inside of that rail then hit her with some lube and all is well.
Ran 200 rounds + through it so far and not one hint of a problem.