[2nd Edit: As with anything on the internet, it may or may not be valuable. After a couple hundred more rounds, the pistol does the OOB hangup just as much as originally. This polishing didn't resolve it, dang it. It only happens with a loaded mag inserted, and I think the extra drag of the extractor bar rubbing on the top round in the mag really exacerbates this. I polished the extractor bar, and that helped a little more. I don't know. Several things happen at that same moment. The trigger bar also pushes against the frame when in the reset position, so maybe there's too much interference there? I may try something to sand away a little of the frame behind the trigger bar. Seems disappointing that this "professional grade" pistol does this. On the other hand, my experience with pistols is admittedly quite limited, and maybe this is just another foible some of them have. This OOB issue could happen in a conflict situation I guess, but if I ever pull the trigger and it moves full travel with no bang I'll have a quick response. Either bop the back of the slide, or more likely go with my extensively practiced tap/rack/bang drill since that will also work.]

The OOB issue has been discussed before here. It's when you have a loaded weapon, chambered round, and push the slide slightly out of battery (up to about 1/4"). It will just stay there, with the trigger not able to fire it. First pull may release the slide, second pull may fire. Sometimes first pull will fire after the slide goes back into battery. Scary for a self-defense weapon to have this issue, since it could be pushed slightly OOB in a lot of ways.

This is due to the way the slide "reset bump" interacts with the vertical tab of the trigger bar. This tab does two things, one is to lift the striker drop safety button, and second is to reset the trigger. The reset happens by the slide's reset bump, really a form of linear cam, pressing the vertical tab sideways. When you push it slightly OOB, the slide will hang up on that reset bump binding sideways with the trigger bar tab.

The LGS dudes weren't any help, but one guy said that a lot of firing may help, like 500+ rounds. So, bag that I said. I'm an engineer, and I'm going to see what I can do. I made up a paste of polishing compound and a little gun oil, dabbed a bit on the trigger tab and the reset bump, and worked the hell out of it. I racked it 100 times (barrel and spring removed), added more compound, and repeated. I did this until I'd racked it 500 times (it goes fast). Now, it will barely do this hanging OOB thing at all, like almost not at all, and if it does, just even tipping the barrel end down a bit puts it back into battery. I'm very happy with it.

So then I decided to look really closely to see just what had been polished by all this effort. I don't know if it's tolerances or what, but the trigger bar tab on my Shield doesn't hit the slide's cam bump properly. It turns out, the trigger bar tab hits the slide's bump at a significant angle. The cam has been worn by the polish so there's now kind of a chamfer on it, and the trigger bar tab has a smallish groove-like feature. The trigger bar tab leans outward when pushed by the slide's reset bump. As a result, the trigger bar tab is only riding the very corner of that bump, easily creating a binding condition. My extensive polishing has created a larger contact area, the visible chamfer, now about 1mm tall.

I think Shield has a problem with how the trigger bar tab is held in alignment with the slide's reset bump. If it held itself vertical, and rode smoothly against the whole face of the reset bump, it shouldn't have this issue. But with it being pushed out of vertical, and only riding against the very corner of that slide reset bump, it binds up. This may be why some Shield's are better or worse about this too.

So, for what it's worth, my fairly simplistic polishing process has taken my Shield from a paperweight to a weapon I'm rapidly gaining confidence in. No more getting stuck out of battery, not even when really carefully trying to make it happen.

Polished area of "reset bump" in slide:
http://i59.photobucket.com/albums/g2...g?t=1447203598

Trigger bar's vertical tab:
http://i59.photobucket.com/albums/g2...g?t=1447203672

Polished area of trigger bar's vertical tab:
http://i59.photobucket.com/albums/g2...g?t=1447203525

[Edit: added photos]

Good info thanks for posting, So far I have no issue's with my 9mm Shield..

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9mm Shield

Nearly every semi auto gun I own will do this (including rifles) if you either ride the slide/bolt when chambering a round or slightly pull the slide/bolt rearward out of battery. So far this has never caused me any issues. When chambering a round, you rip the slide back like you're trying to tear it off the frame and let it go.

This could be a problem when holstering the gun, especially if it's a tight fit. The solution here is to place your thumb on the back of the slide and use it to push the gun into the holster. I've got into a habit of doing this.

Yep, it's not an issue with racking in a round, or even holstering exactly. I use a smart-carry holster, and the weapon sits barrel down in the pocket sitting on the end of the slide. Clothing and body contact cause even more pressure on it, so if it's out of battery and I draw it, there's a real possibility it wouldn't fire. Also, if one is in a SHTF scenario, the BG could push it out of battery by grabbing for it, or you could bump it into them or yourself, any number of ways it could be slightly pushed back. My Ruger can't be made to to this, at all. I don't know, but I'd be real surprised if a Glock does it (don't own any).

With it now "polished", I'm very confident it won't do this in any real scenario, so I'm comfy now!

Interesting thoughts redwing57. Got any pics of the parts in question? I'd love to see them.

Here is a short video on how the M&P trigger works:


Here's a thread listing the parts of the M&Ps:
M&P Parts Identification

It's just for reference to keep us all on the same page. It helps us use the same terminology which makes it easier to communicate what our troubles are.

I like your use of "reset bump" to denote the cam in the slide channel. I don't think anyone has ever given that particular feature a name before. At first I didn't know what you meant, but it became clear as the description went on.

I'm not convinced that the "reset bump" and trigger bar tab are 100% of the issue. However, they are certainly a large contributing factor. Neither do I believe this is really much of an issue.

If the slide gets pushed out of battery by inserting it into a holster, won't it be driven back into battery upon the draw? The holster for my M&P 45 was very tight when new and it wanted to push the slide out of battery. At first I would just push it closed. Then I just ignored it. As I present the gun, it does indeed move the slide back into battery. Now that the holster has been used for a while, it doesn't push the slide out of battery. I really think the issue is just breaking in the holster.

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You posted while I was typing.

Yes, it could be bumped out. Even so, just a little use will stop that from happening. My 45 did that initially, but now I can't get it to stay out of battery even if I try. It just took a little use.

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Freedom isn't free.

Interesting discussion...I guess I just got very lucky! I have no issues and I'm up to a little bit over 1500 rounds through my Shield 9. Two rounds failed to fire but both had a dimple on the primer. I have noticed that I need to holster the gun by pushing on the back of the slide or it will go out of battery but only until the gun is seated and I need to let the slide seat itself when I cycle by hand, but I never thought of either of these as engineering problems.
Thanks guys, I really like knowing what to watch for!

So, this concerned me a bit. I've never noticed this happening but I've never tried to make it happen either, so I tried it with my 9mm. Without a magazine in or round in the chamber, I could not make it happen. Even if I pulled it out about 1/4" (and I tried different lengths) it slide right back into battery. I tried it with a full magazine, no round in the chamber, same thing.

I tried it with a full magazine and round in the chamber and it would stay out of battery...***as long as I kept it level or tilted back*** If I tilted it forward, just a little, like barrel down 1/4", it'd slide right back into battery.

I will say that I have over 1000 rounds through my shield so this may have been something that happened when it was new and doesn't any more.

Thanks for all the thoughts. I'm going to try to get a couple of pictures to show what I was talking about.

I'm sure after a bunch of shots this same wear-in would have happened, and the OOB thingy would have cleared up. Doing the polishing compound was to speed it up.

I really want to start carrying this pistol, since I've lost confidence in my Ruger SR9c that's my present EDC. It has an irregular fail-to-reset-trigger issue that 3 trips to Ruger haven't fully resolved. I'm just tired of fussing with it, and I don't trust it.

So imagine my alarm when this vaunted brand-new Shield more than once simply failed to fire when I pulled the trigger. Yes, I'd not done a proper full-power slide release, but I'd never felt anything like that before from any pistol. This didn't reinforce the wisdom of picking up the Shield, to say the least.

Anyway, I'll try to document with some pics.

I checked mine and it does exactly the same as this. Over 1000 rnds thru it. Does not concern me at all... not easy to get it OOB to start and easily goes back forward. There are so many other things that could go wrong in close up fight. My Shield has been 100% from the start. It is something worth checking though and if it doesn't go back easily there could be a problem.

Thank you redwing57. Putting some lub on the reset bump definitely help. so for sure it's part of the issue.
Also the ammo in the magazine rubbing on the bottom of the rack.
now, I wonder if it's the fact that it rubs on the rack or the fact that it pushes the rack up pressuring it upward

Just checked - The Shield hangs, The Glock doesn't. Both mags fully loaded.

I reload 9mm and had no trouble until I got compact pistols, one of them being a Shield. The cartridge over all length that worked in my full size gun got hung up in the barrel leade and wouldn't quite get into battery and were hard to extract. A little shorter OAL stopped the trouble. I did a LOT of plunk testing in the barrel to get that fixed. Now if I want reloads that will fit ALL of my semis, I have to make them at or below this maximum length.

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Redwing I understand your problem fully and only a few of us really understand what we are talking about. I am a Master 1911 smith but had trouble with both my shields doing this and figuring it out, You have probably seen my threads and it irritates me when these guys come on here and tell me to slingshot the slide etc from all the way back and I am also a Combat Master 1993. I know your pain and understand the skepticism of those who doubt you and also may not even have the cognizance to know their gun does it too.

I believe this once figured out could be fixed with an adjustment rather than material removal. I am going to work on this myslef in the next few days.

As per my comment concerning the short OAL I'm going to try the short bullets for a while, but if I'm not happy with the results I'm going to get my chambers reamed a tad to allow a little more flexibility. I do understand that the magazine and feeding action may limit the size of the cartridge also. There's no free lunch.

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"He was kinda funny lookin'"

Wish I had a 9mm finish reamer. I am going to look for one and also am going to crown my barrels on the lathe because one of my shields will one hole at 7 yds and the other will only do golf ball sized groups. Both have 3 1/2 pound triggers with reset cut into the sears so it is not trigger control.

I would set my factory cartridges with the reamer to barely hang my fingernail on the bl, hood or a tad deeper.

TRY THIS, unload completely and pull the trigger, then move the slide back and forth, nice and smooth when the reset tab is out of the equation with lock up. Let up on the trigger and move the slide back and forth, hangy on the reset tab.

So yesterday when I put some lube on the reset bump I thought it had made it better, but in fact it didn't.
The fact is, if a round is in the chamber and you push the rack forward, after that if you pull it back a little bit, but without cycling it, the rack goes back in position.
But if you put a fresh magazine, and rack it, or fully cycle the rack, putting a new round in the chamber it will hang OOB again.
So it seems like it's something with the angle the ammo goes in the chamber. after the ammo is fully accommodated in the chamber and you pull it a OOB, it goes back in place, but for a new round it stuck OOB.

There's a rib in the slide that the top round in the magazine presses against. It's the thing that shoves the next round in the chamber, the "stripper", I don't know what it's called. But mine did this worst when you insert a fully loaded magazine. You can watch it push up the slide when you squeeze the full magazine in until it snaps in place. That rubbing, between the top round and that rib on the slide seems to be a big contributor.

Even though it might collect a little extra soot, I rub a VERY thin amount of grease on that rib when I lube the gun. Not enough to even see, just a film. I even gently polished that rib with my Dremel's felt wheel and a little rouge compound. Not enough to remove any finish, just a very light polish.

And one other thing, you may or may not be able to make peace with this aspect of the pistol. You can put a little pressure on the back of the slide and put it in battery, holster it, and forget it. I've been assured there are other pistols with this same behavior. They recommend putting your thumb on the back of the slide as you insert the pistol into your holster to make sure it stays in battery. It won't go OOB in the holster, nor when you draw it. Some are dead set against press-checks for this very reason. The Shield is not the only pistol subject to doing this.

Nice writeup redwing. You'll notice that one of the seven lubrication points in the manual includes the top of the trigger bar where it contacts the striker block. That little extra bit of resistance could make the difference between hanging up and allowing the slide to return to battery.

Ok, one more comment for those who may read this far down! One other thing that's happening in that last 1/8" of travel into battery involves the chambering round. If you look closely where the barrel meets the breech face, you'll see because the barrel rocks, that the round is sliding up the breech face, while under the edge of the spent-casing extractor, and may have some pressure there. Also, the two lugs at the top of the barrel (spanning the open spot to visually see a round is chambered) seem to also contact the breech face and ride up just a bit.

This is a little controversial, but I've taken a very lightly oiled q-tip and rubbed over the breech face, extractor, and the barrel lugs. It's a really small amount, you can't even tell it's there. But it seems like anything I can do to reduce friction everywhere will help. Be very careful not to get any oil in the firing pin hole. It will gunk up and give light strikes if you do.

Finally, I'm using Weapon Shield lubes, since they are claimed to help smooth metal surfaces that are under high contact pressure.

Yes, reduce friction using oil or grease when the gun is not at the range and will be used for self-defense. However, the best way to reduce friction is to allow the metal parts to mesh and wear together without oil/grease, for a limited time, during firing at the range. For those people who do not fire their guns (and they are actually in the majority, e.g. city dwellers), cycling the slide by hand without oil or grease is not enough to allow the metal parts to mesh together. Rather, it is the unique stresses during the firing of the gun that best allow the meshing of surfaces. (E.g. see this slow motion video of a gun being fired: https://www.youtube.com/watch?v=7Fr5ccyriJI )

The issue of the Shield hanging out of battery has been discussed since the gun was first introduced. It is principally caused by the strong upward pressure of the top round in a fully loaded or nearly fully loaded magazine, hitting against the slide's loading rail. Other combinations of causes include the pressure of the extractor against the chambered round's casing, the trigger disconnector riding the bump in the slide, and the barrel-to-slide lock up points of contact.

Inevitably, people always fail to discuss that it is the job of the recoil spring to overcome all of the above mentioned forces of resistance. However, people who replaced their recoil spring reported that it did not eliminate the problem. The solutions discussed are to apply a very small amount of grease (not oil) on the disconnector bump area on the slide, to apply a light coating of oil (never use grease!!) to the slide's loading rail, and to reduce rounds in the magazine by -1 from the maximum (e.g. 6 rounds in a 7 round magazine).

In my Shield, the principal cause of hanging out of battery is a fully loaded 7 round magazine... but not a fully loaded 8 round magazine. Rather than carry -1 in the 7 round magazine, I am going to try the MagGuts product and only load 7 rounds in it.

No, this can't be part of this problem. The trigger bar only contacts the striker block when the trigger is held back.

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My ported 9 does an OOB thing in the middle of a mag occassionally, but more so with a SS RSA upgrade I have. When I put the OEM RSA back in, it does it very seldom - so, I think that has something to do with it; i.e., the spring and the slide weight (or in my case, lighter weight; ergo less momentum going forward to close due to the porting, especially on a slightly imperfect round (bullet seat, case dimension, etc - factory ammo; not reloads). Check the under side of the slide top and see if there are little drill indentations where they milled out slight bits of material to "balance" the slide, or get the weight "just right". I think S&W knows they've got a problem or issue in this area. As an engineer also, there's my two-cents worth, and thanks for the bump theory. I'll give it a bit of a polish just for the hell of it.