Hello, I am new to the forums and new to the S&W family. I bought my SD40VE about a month ago and have put at least 500 rnds though it. I had Failure to feed problems at first which had gone away after the first 200 rnds, now I am getting slide lock problems. I first noticed that the slide locked back with ammo still in the mag, i looked at the chamber and noticed that the round seemed a little off or crooked. So i pull down slide lock and was fine, round went right in and shot. This continued a few more times and then noticed that the pin on the left side of the gun(above trigger) was coming out half way so i slid it back in until it locked or think it did, heard a click. I shot about a 100 more rounds and the slide continued to lock, Pin never came out after the intial one. I brought it to a gunsmith, he asked how i held my gun to see if maybe my thumb was pushing up on the slide lock causing it to lock, It wasnt pushing on slide lock. He said that he just need to apply more spring tention in the slide lock. So i paid him 30 bucks to tighten the spring which didnt work. Can u guys help me to fugure out what is wrong.

Call S&W...they'll send you a shipping label, and they will fix it (I assume you bought it new?) There is no need to pay or have a local gun smith fix your gun.

Does this happen with both mags. ?

Are you shooting different ammo then before ?

3

I will call smith and wesson. Yes I shot PMC, Winchester, federal and american eagle and its happening with all of them. Both magazines as well.

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I had this same problem, tried different ammo, got sigma mags, used a different grip, and slide always locked back at least once each mag. Finally noticed that each time it happened, the top round in the mag when it locked was not seated at the back of the mag. It appears that during cycling, the top round is carried forward a little bit and the front of the round was catching on the little tab on the slide lock that the magazine follower pushes up when the magazine is empty. I was able to file down the tab so that it was short enough that the forward seated rounds don't catch, but the magazine follower does. I was careful to only file a little bit at a time so as not to take too much off. I didn't even have to take the slide stop out of the frame; I was able to file it with just the slide taken off. I tested to see if the rounds were catching by simply inserting a mag with a round in the frame (while the slide was off).

Took it to the range yesterday and went through 6 full magazines without an issue.

Sounds like limp wristing maybe the problem.

It is easy to grip when not shooting and say that you aren't interfering with the slide stop. However, a lot of people do not notice that when firing, they tend to lose track of where their thumbs are and the recoil causes their thumbs to move and occasionally push the slide stop up. Be very mindful of your thumbs when firing.

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M&P40c/15-22/SD9VE/Mossy500

I've had a couple SD40s for about 15 years, and the exact same issue pops up now and again (every couple hundred rounds). I initially sent the pistol back to S&W, and they replaced the slide stop. Same random occurrence of the issue. Examining the pistol when it happens, I came to same conclusion you did.

The problem is that the magazine feed lips are losing control of the top round under recoil, and it moves forward. The design of the slide stop engagement tab is such that when the round moves forward under recoil, the bullet ogive engages that tab and it's enough to lock the slide back. The .40 round has a relatively fat and blunt ogive, compared to the 9mm round most of these guns were designed around.

The problem can occur in any lightweight pistol firing ammunition of substantial recoil for the weight of the gun. The .40 round is hard on pistols basically designed for the lighter recoiling 9mm. I've seen this issue occur in .40 Glock pistols also, when the various springs start wearing out. In that pistol, the usual cure is to replace the recoil spring, magazine spring and slide stop with spring, and function is restored.

With the SD40, IMHO the design of that tab is the major individual issue. You would probably not see this malfunction in the SD9 as the smaller diameter bullet is farther from the slide stop engagement tab - the same part is used for both calibres. After S&W replaced the slide stop and the issue persisted, I modified the tab in the same way you did. Haven't had any problem afterwards.

I also change the recoil and magazine springs every 3000 rounds.