.40 S&W M&P failure with Hornady TAP ammunition

[Warhammer4k]

My S&W M&P in .40 S&W has been utterly reliable for years, so I'm very surprised that it malfunctioned when I was shooting some carry loads (Hornady TAP .40 S&W 180 gr. JHP) at the range last weekend.

The malf's were feed failures. I got 3 or 4 failures in shooting 2 magazines of the Hornady TAP ammo. No pictures, but they were the type of failure where the next cartridge sort-of starts to feed, but then jams up against the chamber roof, or partway into the chamber. Magazines were firmly seated when these failures happened, and I was shooting exactly the same way I've shot thousands of rounds through the pistol without the first problem. So I'm baffled.

I inspected all of the fired brass. None of it was abnormal in any way. I'm sure I would have noticed if any of the rounds had been oversized out of the box, to the point that they wouldn't fit in the chamber. I doubt they would have fit in the magazine if that were the case.

I went on to shoot several magazines' worth of reloads (180 gr. FMJ bullet on 5.0 grains Bullseye) without a single failure. This is more of the same thing I've seen with thousands and thousands of rounds of my reloads in the M&P: they just work.

It's almost as if my M&P is perfectly reliable with reloads, but won't work with "quality" factory ammo!

I don't know where to even start diagnosing this problem. Any ideas?

Edited August 9, 2012 by Warhammer4k

[lee blackman]

I'm putting my money on cartridge over all length. Just cause its factory doesn't mean its perfect, period.

I've had it happen to me before with factory winchester .38super ammunition. I bought two boxes off the shelf at the local Academy cause it was the only brand they had. When I shot up the last bit of fiocchi I loaded up the winchester. It kept sticking in my magazine. I kept having failure to feeds. I pulled the base off my mag and got the remaining cartridges out, opened up the other box of the same stuff and the same thing happened. Being a reloader, I was going to pull the bullets and save the components, I mic'd a couple of the cartridges to find out they were longer the spec OAL for .38super. One by one I ran them thru my seating/crimp die to push them futher in the case, and wha la! They functioned just fine.

[Sin-ster]

It may just be that the bullet profile doesn't jive with your feed ramp.

Have you shot any other expansion-focused JHP's through the pistol before? Any similar to the shape of the TAP round?

[Warhammer4k]

What's really disturbing about this is that Hornady TAP was my carry ammo. I tested several magazines' worth a couple of years ago, then shot a couple of magazines every 6 months or so just to make sure I could still hit stuff with it, firing a lot of reloads in the meantime. TAP always worked. Reloads made with Hornady XTP bullets (the same ones in TAP) likewise worked. If there's a problem with the XTP bullet and the M&P feed ramp, it's a new one.

Going to give it another try tomorrow afternoon, starting with a squeaky-clean gun. The M&P was dirty before the range trip where TAP failed, but not THAT dirty. It shouldn't have had feed problems just from being a little grimy. If I have malfunctions again, this time I'll take pictures.

[lee blackman]

With factory ammo, you have to pay alot of attention to the LOT number. Basically every LOT is a different load, even if its technically the same, its still a different run, and there will be variations between each lot, sometimes slight, sometimes drastic. You'll find on occasion there are specific recalls on specific LOTs. And nothing mechanical is ever 100% reliable, so you should always train yourself to handle malfunctions. And be open to other options, in case the particular brand/model of ammunition you prefer isn't available. Its good to get a feel for other stuff off the shelf.

[Warhammer4k]

All of the TAP is from the same lot, so go figure why it worked before but won't now.

To clarify, the problem ammo is the plain brass-cased TAP CQ that comes in a red box, product number 91365. All of it is from the same lot number (3090622). I started with a couple hundred rounds of it, and am now down to about 100 (5 boxes). I suppose it's time to consider a completely different ammo choice, such as Gold Dots.

Anyway, I shot some more of the TAP again earlier, starting with a spic-n-span gun and two magazines I had also cleaned. I had 3 failures, and thought to take a picture of one of them:

That's what the failures last week looked like, too.

I measured a few cartridges - all were right around 1.123" COAL, which should be OK. My reloads tend to be longer, and they work fine.

I think a call to S&W is in order. Maybe Hornady too.

update:

S&W's response: "That's weird. Send it in." They provide a prepaid shipping label, so that's really easy to do.

Edited August 13, 2012 by Warhammer4k

[Sin-ster]

Yep, I'm baffled if you've shot TAP through it before without issues.

It almost looks like the extractor claw won't pass the rim, in the picture you took. I can see that happening on a new gun, but... not an old one. (Unless you've armorer stripped/replaced some things...)

I suppose it could be the result of a magazine, but... I'm guessing you tried several different ones, checked the springs and lips, etc.

Can you smack the back of the slide to get the round to fully chamber and the gun to go into battery? That'd be one seriously borked recoil spring if it was the ONLY problem, but it might be why you've just run into it (exacerbated by something else).

[RWF]

recoil spring? maybe?

maybe the tap needs a liitle extra push. just quessing.

[redial]

Same problem you're having with the Glock 20?

[okshootist]

If you're using the same magazines, I would start there. It's possible that the springs have weakened and/or the feed lips are no longer in spec and your reloads are a little more forgiving than the TAP rounds.

[Warhammer4k]

Can you smack the back of the slide to get the round to fully chamber and the gun to go into battery? That'd be one seriously borked recoil spring if it was the ONLY problem, but it might be why you've just run into it (exacerbated by something else).

I didn't try smacking the slide, but hitting the magazine from the bottom does make the stuck round chamber. So it's not as if there were something preventing free movement of the slide and recoil assembly. The cartridge just kind of..gets stuck, for no apparent reason.

I'm sure S&W will try brand-new magazines as part of repair service. Mine sure look fine, and I have 10 of them, so it's not as if I'm constantly using the same 1-2 mags.

I don't know when I'll get to send it in exactly. I made the warranty request yesterday, but still haven't received the prepaid shipping label email. I expect a human being at S&W needs to review & approve the claim, so it will likely take a few days.

Edited August 14, 2012 by Warhammer4k

[Babaganoosh]

For what it's worth it might have something to do with the OAL. I reload and at 1.125 I seem to have jams. 1.135 and they run with no issues. Probably not the problem since you have run them before, just throwing it out there.

[Warhammer4k]

Got it shipped on Wednesday so S&W should get it today. I don't know how fast their turnaround is, but I assume it will get overnighted on the way back, so I might be back in business by next weekend.

I hope this gets resolved. I was planning to use the M&P in an Ayoob live fire course in October. There wouldn't be much point in using a gun for the class that I can't carry because it won't work with defense ammo.

[Warhammer4k]

Good news, everyone!

I got my M&P back on Wednesday. Took it to the range this AM. It's once again working perfectly.

Unfortunately, I used all remaining 105 rounds of the Hornady TAP to verify function, so I'll have to order some more.

I also shot a box of Blazer and some handloads just to be sure.

S&W put in some new parts, including a new-style slide stop. It's much better than the old one. Anyway, the gun works again.

[Warhammer4k]

This story doesn't have a happy ending just yet.

Something about the new-style slide stop keeps the gun from locking open on an empty magazine with 7 out of my 10 magazines. I first noticed this at the range last weekend, shooting reloads and CCI Blazer. Wasn't quite sure what was going on at the time, but knew something wasn't right.

At home, I tested all of my magazines empty, with the gun also empty, and found that only 3 of them will reliably activate the slide stop. Most of them never activate it; one does so occasionally.

With the slide removed from the gun, all magazines push the slide stop up far enough that you'd think they would also do it with the gun in one piece. Not so.

So I don't know what's going on here. Have I managed to wear out 7 of 10 magazine springs? All the magazines are of a similar age, having been purchased within a year or so of when I originally bought the gun. Doubting the "worn mag springs" idea since this never happened with the old slide stop.

Going to call S&W about this Monday. Until then, any ideas?

Edited September 7, 2012 by Warhammer4k

[Warhammer4k]

I'm pleased to report a happy ending to this story.

I received a package from S&W last Friday, which contained five each of new magazine springs and followers. I swapped them with the old springs & followers in five of my known "problem" magazines, and it fixed the problem right away. I made sure, by shooting the gun using those magazines the next day. It reliably locked open on an empty magazine, once again.

S&W is pretty awesome. Now I just need to order five more springs & followers, so I can do preventive maintenance on the remaining magazines.

FWIW, I ended up buying Speer Gold Dot LE .40 S&W (product 53962) as my new carry ammo.