S&W M&P 40 Mod 2.0

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bdb242

bdb242

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Became the proud owner of another .40 S&W last Monday. Model M&P Mod 2.0. Finally got to fire this piece yesterday. After running 12 rounds through it in a slow and deliberate manner I was impressed with the accuracy of the 4.125" barrel. The problem is with the condition of the ammo. I was firing a 135 gr Nosler JHP load in new R-P brass over 9.9 grs of Longshot with CCI 500 primers. Max load is 11.5 grs. of Longshot. COAL was 1.125". 6 of the rounds fired were normal in every respect. 6 rounds had perfectly flat primers, and I mean FLAT. I'm going to try and post a few pictures. The empty cases ejected 8-10 ft high and traveled 10-12 ft to the side.

I de-capped two of the primers to measure them. Normal primer measured 0.120". Flat primer measured 0.113. Both primers came out of the sale pack. I pulled a couple of bullets and re-checked the powder. 9.9 grains on the dot.

Any ideas? Checked headspace, going to call S&W tomorrow to get the specs of what it should be. Measures .0065" right now. I have 88 more rounds loaded, sometime this week I'm going to run a few of these rounds thru my Hi-Power to see how the primers look in it.
 

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Did you start low? Maybe the XTPs go deeper into the case than the nosler JHP that's listed in the data.

Also... stupid question, but are you SURE it was Longshot?

Are you SURE of the OAL?
 
Not sure what I'm seeing in your pics... are the bottom two primers decapped primers that you placed on top of empty cases or what is that?
 
Yes it is Longshot, COAL came from Hodgdon's web site for that bullet, and yes the those primers were removed from the cases they are sitting on to measure the thickness. Going to fire some factory ammo today if I have time to see what happens. I think headspace is excessive after talking to a pistol-smith last night who called me.

Changed the info a little after I looked it up again. The info for the load is correct as posted. Nosler 135 gr JHP is the bullet specified with the Longshot data.
 
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Fired 1 factory round, a 180gr Winchester load, case ejected shoulder high and landed about 5' from my shoulder. 4 rounds of 135gr Sierra JHP with 7.7 gr HS6 were tried next and recoil and ejection was identical to Winchester factory load. All primers were normal. I'm picking up 50 Nosler 135 gr JHP bullets from a friend tomorrow. Going to start with 8.5 grs of Longshot and work up .2 gr at a time and see what happens. Anxious to see how this goes.
 
I loaded 4 rounds of 135 JHP Nosler with 8.8 grains of Longshot with a COAL of 1.129" using CCI SPP. All fired with normal looking primers and no ejection problems. Loaded 4 rounds with 9.0 grains of Longshot and had 4 more flat primers and cases ejected within 18" of the 8.8 grain load, COAL was 1.129". I guess the max load for Longshot in this pistol is 8.8 grains. Accuracy was amazing to me. The 8.8 gr loads were the 2 two shot clusters at 20 yards offhand, and I am not a good pistol shot. Next will be a chronograph session to check velocity.
 

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Yes, all rounds have been "plunked" before firing. No issues with feeding either.
 
I'm confused. The picture in your first post of the flat primers don't look the least bit flat to me, but I'm no expert. I see a nice radius on the outer edge of the primers. I probably need to be educated about flattened primers.

I'll be interested to see your chrono results.
 
For 40 S&W, Hodgdon shows the starting load for 135 gr bullet to be 8.5 grains and the max load to be 11.5. So at 8.8-9.9 grains, you are toward the lower end to mid range of manufacturer recommended charge weights. And your primers don't look at all flattened to me. Have you chrono'd the load to see if your velocities are in the range that the manufacturer states? The primer pics above suggest to me that you are good to go.
 
Here's a flattened primer. It's a 357 and not a 40, but I couldn't find any of those.
 
My primers on the .40 loads were completely flat, there was NO firing pin indention at all. Primers were not swelled around the edges as your 357 shows as a high pressure load should. The firing pin indention is what has me really confused. 8.8 grs of Longshot behind a 135 gr Nosler JHP all looked normal. Two of the four 9.0 gr. loads showed no primer indentations. In the picture I posted the two cases on the right have no primer indentations, there is a ring on the primer from the bolt face surrounding the firing pin. These loads ejected a good 12 - 14 feet high and traveled a minimum of 12 feet from me. I had one of my sons watching the brass as I could not find several of the fired cases to check the primers. Apparently several of them landed on my roof and rolled into the gutter.
 
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Now I think I understand your problem better. It seems that you are getting some unusual signs. Cases being ejected farther than usual might indicate higher than normal slide speed. And you are seeing that where there should be a dent in the primer from the firing pin, that depression has been somehow pushed out so that it is essentially flat with the surface of the primer. And the edges of the primer are still round indicating that the loads are not over pressure.

In 25+ years of reloading I have yet to see what you have observed. I've had pierced primers before, notably with 400 Cor-Bon and 9 mm major using small pistol primers, but never have seen the firing pin dent pushed out to be flat with the primer surface.

As an aside, one of the fascinating things I find about reloading is that you run into problems or issues that require thought and experimentation to resolve. As a retired research chemist I have to say that I love this problem solving.

Anyway, I'm puzzled by what you have observed. Having never seen this before I would look to ammo first and then would consider if the problem could lie within your M&P itself. I might try running a box of factory ammo to see if you can duplicate the problem. And then I'd try your reloads in a different firearm to see if the problem transfers. Since I know next to nothing about M&P's, if ammo turns out not to be the problem, I'd be looking to other M&P owners for help.

Just my two cents worth. I hope you find the solution.
 
The .40S&W is a cartridge extremely prone to overpressure. I didn't quite understand what exactly your primers look like after shooting because the photo is very bad. After you upload a photo it would be even better to click on "full image". However it could also depend on the breech face and how the firing pin acts and how it comes back after hitting the primer (see Beretta 92 pistols). I would also control these things.
 
Found a new Springfield XD 4.5" barrel .40 at a good price, going to get it this afternoon to check the ammo / different gun theory :). Also found some ammo on the shelf. Why not.?!

Picked up the XD yesterday. It is an XDM and the date on the factory shell case envelope was 2013. The envelope was still sealed. Pistol is brand new! Apparently it was overlooked in storage and was just put out along with another XD in .40.
 
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Finally fired some 10.0 gr. Longshot loads under the 135 gr Nosler JHP in the new Springfield XDM-40 that was way to hot for my S&W MP 2.0. No issues at all with the XDM and it really liked the 10.0 gr load. Very accurate, 5 shots in 2" at 20 yards and I'm not a very good pistol shot either. Must have been luck. 8.8 grs of Longshot is all the S&W can handle with the 135 gr Nosler bullet. Oh well.
 
bdb242 said:
Fired 1 factory round, a 180gr Winchester load, case ejected shoulder high and landed about 5' from my shoulder. 4 rounds of 135gr Sierra JHP with 7.7 gr HS6 were tried next and recoil and ejection was identical to Winchester factory load. All primers were normal. I'm picking up 50 Nosler 135 gr JHP bullets from a friend tomorrow. Going to start with 8.5 grs of Longshot and work up .2 gr at a time and see what happens. Anxious to see how this goes.
Click to expand...
Might be the best way to go. That is a very High velocity load. best to work up slowely. I love Longshot in my 10MM Glock. Are you running thru a Crony? Did you Try the 10 grain load in the M&P???
 
No, haven't tried the 10 gr load. The M&P really likes an 8.8 gr charge of Longshot under the 135gr Nosler JHP. Just going to stick with that. When Spring gets here I'll see what the velocity of the 8.8 gr load looks like and compare it to the 10.0 gr load in the XDM-40.
 
I would run some factory ammo thru it.

I would also try some handloads with a faster powder, like WST, or titegroup

I would NOT call S&W and talk about reloads
 
Ran some 135 gr Federal PD Hydro Shocks with no issues. No issues with factory 180gr Winchester FMJ's with no issues. I have no other factory ammo to try at this time.
 
Spent some time yesterday with my Quick Load program checking out the published data for the Nosler 135gr JHP and Longshot powder. Published max load of Longshot with the Nosler 135 gr JHP is 11.5 gr. According to Quick Load a 11.0 gr load produces 35,878 psi of chamber pressure. SAMMI rating is 35,000 max for a .40 S&W. At 9;9 grains a maximum average pressure warning is printed due to tolerances that may cause dangerous pressures. Apparently my S&W tolerances create such an issue, while the Springfield XDM has so problems with a 10.0 gr load of Longshot and the Nosler JHP. The 10.0 gr load produces 28,450 psi according to the data in Quick Load. Actual velocity testing will have to wait till another day. I will be looking for around 1150 fps with 8.8 gr in the S&W and 1300 fps with the 10.0 gr load in the Springfield. More to follow later.
 
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