What causes pistol rounds to nosedive and cause a jam?

[groundskeeper willy]

Got a weird issue.
Bought an Smith and Wesson SD40 in .40 and it was used but low mileage.
Sat in safe for several years unfired.
Finally get it to the range and its jamming almost every shot.
What happens is the round nose dives and the primer end is sticking out of the slide.
If I am lucky I get two shots before it fails.
I have cleaned the gun several times immaculately. No visual defects. It looks like new.
Lubed it as well until it was dripping and still fails.
Shot it dry as well and still fails.
Tried all three mags I have and still fails.
Tried different brands of ammo and still fails.
Definitely not limp wristing it. Range staff also tried it and it failed in same manner.
Feed ramp looks nice. No burrs or rough spots.
Mags disassembled and cleaned too but they looked great to begin with.

Any advice as to what it could be?

 

[Ribstaylor]

Recoil spring not doing it's job like it is supposed to?

 

[wasrupzuk]

Maybe mag spring is weak or in backwards?

 

[colinjw]

Maybe mag spring is weak or in backwards?

OP said he tried 3 mags so possible but unlikely.

 

[Still alive]

Does the round load normally when you manually chamber the first? What happens when you hand cycle all the rounds from a mag? Just checking if you have an extractor or ejector problem.

 

[groundskeeper willy]

Does the round load normally when you manually chamber the first? What happens when you hand cycle all the rounds from a mag? Just checking if you have an extractor or ejector problem.

If I cycle the slide by hand slow it’s guaranteed to nosedive.
If I cycle by hand normal speed its 50/50 if it nosedives.

 

[Still alive]

Ok, so the gun ejects all spent cases no problem, right? Just nosedives during the forward movement of the slide, while stripping the round off the mag? And it happens while firing and manually?

I know you have tried 3 mags but it really sounds like a mag issue.

Dumb question. You said your gun was a .40S&W. Could it be you have .40 mags but it’s actually a 9mm? The rounds will be looser in the mag and can nosedive. I’m really reaching here.

 

[cooperod]

Sounds like extractor needs tweaking. If you place a fired case under the extractor flat against the face, is it hard to get in? Does it hold the case in place firmly?

 

[just having some fun]

What does it do when you have 1 round in mag and Rack slide ?

What does it do when you have 2 rounds in mag and Rack slide ?

 

[Juster]

Could be squished feed lips on the mag.

 

[highlander]

Maybe mag spring is weak or in backwards?

My thought also.

I could be that the original owner had the mags apart and put the springs in backwards; it can happen easily enough.

Try reversing one of the mag springs and trying it.

 

[Sniper_485]

There is a possibility that your gun hates that brand of magazine. You could try a different brand. $0.02

 

[colinjw]

Is the mag catch locking the mag all the way in ?
Perhaps the mag is being held just a little bit low causing the
nose of the bullet to not go up the feed ramp properly ??

 

[Tex Critter]

I had that same problem. Mine was fixed after I found out 3 of my mags were actually 9mm vice .40S&W.

 

[CoreyMac]

I realize this has been suggested but I had a real bad nose dive on my new sig 1911, I tried 3 different brands of mags and nothing seemed to help. One fellow on here suggested the mag spring was too stiff , said to load a full mag up and let it sit to reduce the spring pressure a bit. Damned if that didn't fix the issue. The round was being held so tight it wasn't sitting properly in the mag. Maybe try a mag with only a few found apposed to full.

Sorry if I have repeated any suggestions. Just going with what worked for me.

Corey

 

[marshall]

That is a mag problem I would think, yes I know , 3 mags 3 problem, it was used , so you don't know what happened before. mags too low in the gun, but don't know how that could be

If I cycle the slide by hand slow it’s guaranteed to nosedive.
If I cycle by hand normal speed its 50/50 if it nosedives.

 

[marshall]

I have used 9mm ammo in 40 mags O.K. have not tried it the other way, but should not matter, the follower/ next round is suppose to hold the case for a push into chamber. A .40c round would sit lower in the mag, so that could cause a problem.
If you look at the springs, the high end of the loop is always at the front.

 

[cooperod]

Since it fails every time on a slow feed, it will likely be the extractor not correctly seating the round under it. But hey, mag trouble shooting is simple to start.