M&P Shield .40 S&W Kaboom

[Bob K.]

I put my first rounds through a new Shield .40 today. At around the 40th round, I experienced a cartridge detonation and case-head separation in the ejection port. I've been following the kaboom and case bulging threads and I offer this additional incident as a data point. I make no judgments at this time because this certainly could have been my fault.

Here's what I know.

• Serial # is HMXxxxx
• It was a reload.
• Is it possible that I could have overcharged the reload? Sure. If I did overcharge it, it would be the first cartridge in 20,000 rounds of reloading across 13 calibers and 18 years.
• Was the brass old and/or weak? Possible. I never use brass cleaner (to avoid weakening the brass) and only use walnut media for cleaning. Hence the staining on the brass. The brass could be up to 18 years old but could be only reloaded a couple times. I hand-inspect each piece of brass before reloading.
• I had regular FTFs in those first 40 rounds. I was shooting FMJs and lead semi-wadcutters. The lead semi-wadcutters FTF'd pretty regularly. Some of the FMJs also failed to feed and I had one FMJ that had a significantly set-back bullet as a result. (Note: I put a meaty taper crimp on all semi-auto rounds and I don't experience FTFs with these rounds in my Beretta 96F.)
• I inspected my brass after the session and I had significant case bulging on about 10% (about 10 cartridges) of the rounds I fired. I wasn't paying attention enough to associate the bulged cases with any particular bullet. These are middle-of-the-road reloads that I previously loaded up for my Beretta 96F. I intended to throw a variety of rounds at the Shield today to gauge its ability to eat what I give it. I'll pay more attention and be a little more methodical next time.
• On several cartridges, I needed to tap the back of the slide to put it in battery.
• No squibs. All bullets clearly came out of the barrel and hit the target.
• Other than some power and brass fragments to the hand and face, there were no other flying bits. (Thank you, eye protection.)
• Post-incident inspection showed no damage to the firearm and I continued to fire it after the detonation.

Again, no judgments yet. I plan to watch closely for further problems.

 

[Coastie762]

Lot of good information in your post. You noted that you experienced bullet setback with some of your loads. It's possible that setback caused your detonation. The .40 operates at fairly high pressures, bullet setback during chambering can cause pressures to skyrocket.

When I first started loading .40's I noted problems with setback on some of my loads. The problem was due to insufficient sizing. Even with a healthy crimp I found it possible for the bullet to be pushed back into the case during feeding. To correct this I purchased a sizing die from EGW, this was essentially a Lee carbide sizer ground slightly undersized. This worked quite well to eliminate that problem.

Was the detonated round a jacketed or lead load?

 

[M29since14]

Sounds like you were having a LOT of trouble with your handloads. First question, does the gun work normally with factory ammunition? If so, your handloads probably need considerable refinement. As to what caused the problem, it sure sounds like bullet setback during feeding, given the information supplied.

 

[robert1804]

Great write-up, Bob! Your Beretta 96 is very unlikely to have set-back problems since it feeds cartridges nearly straight into the chamber, unlike most other automatics.

Proper case tension is needed to prevent set-back. Taper crimping is not effective to hold bullets. As Coast762 said, an undersized sizing die is helpful, especially with thinner walled brass.

 

[epj]

I have long been suspicious that the Shield can and will fire in a slightly out of battery condition. I have pretty much stopped shooting both my 9 and my .40 as a result of this suspicion. When I get time, I may dig them out again and do some more looking into it. As to the OP, good possibility of bullet setback. Or, might have fired just out of battery.

 

[Ole Joe Clark]

Did you do the "plunk test" after reloading the shells?

 

[NCW Ray]

I find your thread title "M&P Shield .40 S&W Kaboom" very misleading. Sounds to me like it should have been titled "My Reloaded Ammo Kaboom". And probably should have been posted in the Reloading section.

 

[LAA]

I have long been suspicious that the Shield can and will fire in a slightly out of battery condition. I have pretty much stopped shooting both my 9 and my .40 as a result of this suspicion. When I get time, I may dig them out again and do some more looking into it. As to the OP, good possibility of bullet setback. Or, might have fired just out of battery.

Based on this, and the fact I've never been suspicious about it, probably because I haven't had the need to think about it.....

I did try my 9mm & 45 ACP Shield. I don't have a 40 Shield. Thought I might even go to the trouble of loading some primer only cases, and load them through the mags. But I didn't get that far. At least not yet.

Pushing both the 9 & 45 just very slightly out of battery, the trigger pull actually forced it back into battery, or the trigger wouldn't release the firing pin. Based on that, I don't think I'll bother with the primed cases.

Other than that, both of these two pistols have had a tremendous amount of rounds put through them. These include many types of factory loads, and numerous combinations of reloads. I've had no reason to doubt them. These two, are my carry guns. If there was any suspicion regarding operation, they wouldn't be.

 

[Hillbilly77]

Post-incident inspection showed no damage to the firearm and I continued to fire it after the detonation.

Is that a crack in the feed ramp in the first picture?

If the feed ramp is cracked, the chamber is weakened and I wouldn't fire that gun anymore until it was fixed.

 

[LAA]

Is that a crack in the feed ramp in the first picture?

If the feed ramp is cracked, the chamber is weakened and I wouldn't fire that gun anymore until it was fixed.

I think that's just the casing with the crack.

 

[Hillbilly77]

I think that's just the casing with the crack.

Ahh.
Good call. I see it now.

 

[model3sw]

This exact problem happened to me just about 6 months ago. A 469 ANIB that had been in our collection for 25 years. Gifted to my eldest son on that day.

We first fired some of my personal target ammo with no problems.

But here's the issue. Over the years with collections purchased much loose reloded ammo was collected. That day we were just 'wasting" some of the old ammo to use it all up.

My son firing this 469 for the first time out of the box after years of storage. It blew one of the grips off (the 469 grips interlock and snap in they are not screwed in). EXACTLY the same with the the bottom of the case blown off.

The ammo was noticeably BULDGED at the bottom, near the rim.

What happened was that the firing pin was till active even though the slide did not completely seat.

The same ammo on a Sig 226 when the side did not seat the firing pin was not active. thus would not fire.

I believe if your slide was fully seated, this may not have happened.

Thankfully. no one was hurt and the 469 was not hurt.

We examined all the loose / old ammo and sized the base of the cases with a micrometer. We removed and disposed of, just that one box of ammo with the buldged cases.

Likely the person who reloaded these did not use the proper sizing dies and / or method of resizing.

I've noticed this in the past with cheap grade reloaded ammo. About 20 years ago, I and friend were using up the older reload ammo, in stock, at a local PD range here in Florida, where he worked.

That time in the past, all that happened was it would not seat fully on a Sig 226, thus would not fire.

It is a matter of if the firing mechanism is live even when not seated fully or as in the Sig 226, the firing mechanism is inactive unless the slide is fully seated.

 

[LAA]

snipped
I believe if your slide was fully seated, this may not have happened.
snipped
That time in the past, all that happened was it would not seat fully on a Sig 226, thus would not fire.
snipped
It is a matter of if the firing mechanism is live even when not seated fully or as in the Sig 226, the firing mechanism is inactive unless the slide is fully seated.

So, who else has a 40 Shield to test? My 9 & 45 Shield will not fire, unless the slide is fully seated. I'd rather see actual test results here, than just conjecture. So far in this thread, it's a case of opinions, without facts.

 

[model3sw]

So, who else has a 40 Shield to test? My 9 & 45 Shield will not fire, unless the slide is fully seated. I'd rather see actual test results here, than just conjecture. So far in this thread, it's a case of opinions, without facts.

My statements on 469 and Sig 226 are factual and re-tested to affirm. I offered a probable cause to the problem on the Shield, while stating facts as related to the S&W 469 and Sig 226 used in my scenario.

As I wouldn't own a Shield, a few of you should give it an honest test instead of just a statement that the Shield sill not fire unless the slide is locked and fully closed. Further, a similar vintage Shield should be used.

Before you say it will or it won't ... make sure the magazine and chamber is empty, close the slide gently on a 1.5mm hex key (with the right angle of the key protruding from the top of the side) a bit off center from the firing pin (in case it does strike you won't hurt your firing pin) and pull the trigger. After the 1.5mm hex key try a large metal paper clip, opened up with the wire end down in the chamber to keep the slide back that small distance.

Beside the above as ONE scenario that might cause it there are multiple instances of the .40 S&W Shield exploding. Here are a few, then GOOGLE it yourself.

There are plenty of reports of the Shield 40 exploding similarly, here are only 2 :

http://smith-wessonforum.com/smith-wesson-m-p-pistols/359609-sadly-another-40-shield-kaboom.html

http://smith-wessonforum.com/smith-wesson-m-p-pistols/372544-m-p-shield-40-blow-up-3.html

 

[Bob K.]

Great conversation so far.

• Yes, this could be my fault. I'm really confident with my reloads, but certainly, I could have done something wrong. Perhaps I've been lulled into accepting less-than-perfect reloads because my Beretta 96F is so darn reliable and shoots anything I give it. Perhaps the Shield is more precise (finicky?) and I need to be sensitive to that.
• I don't know if the detonated round was an FMJ or a lead semi-wadcutter.
• Yes, bullet setback may have been the problem. The detonated round was a full speed cycle into the chamber and gave no indications of hanging up. I'll check my sizing die and taper crimp to make sure I'm getting what I need.
• I haven't fired factory loads yet. That's my next troubleshooting step.
• In another KB thread, a member suggested the unsupported chamber may be less tolerant of marginal brass and that a perfect combination of conditions could result in a case blowout. Maybe that's what I experienced and I'll need to be a little more diligent with brass. The bulged brass indicates I need to consider it as a factor.
• I'll check for OOB problems. With an empty chamber, I've noticed I can pull the slide back approximately 1 to 2 millimeters and still drop the hammer. Because alignment slightly changes, I'm not sure if it would actually result in a primer strike if there were a cartridge in place.

 

[mrmike7189]

ouch that could have been a lot worse!

 

[Flash_80]

Tried this just now on my Shield 40. I could get the striker to fire if I pulled the slide back just a hair to where the barrel started to tilt. Could not if there was any space between the lug and the frame, but I could make it go when the barrel had just a bit of tilt and the slide was not completely forward.

Tried on my FS40 and my P99 as well. They did the same, albeit not quite as much tilt. FS40 less so than the other two.

 

[jim46ok]

1. Measure a factory round casing with your reloads.
2. Measure chamber size and compare to your 96F.

All mfg have a SAAMI spec to follow. Manufacturing variances sometimes exceed (one way or another) these specs. I wouldn't be surprised if your measurements show a smaller chamber on the M&P. And as stated, maybe not a true "full length resize." Your die might be slightly big......JMHO

 

[OldLawman]

If not already noted by someone else, Glocks in .40 have had similar issues.

Just one of the several reasons I decided against the caliber. If I want something bigger than a 9mm, I move up to .45 acp. The pressure curve differences in .40 seem to be one of the root causes.

 

[yep380]

I'm trying to imagine how a reload (or any round) could go off out of battery. Would a primer sitting proud possibly contact the breechface as its being cycled/chambered... could that do it?

Did you pull the trigger on this round, or did it go off as the gun was cycling?