Frustrating day at the range (M&Ps)...

[tydephan]

So tonight, I loaded a few rounds just to make sure I was seating the primer all the way down.

I loaded 30 rounds. Same formula as listed in the original post, except I used once-fired RP brass this time.

15 rounds through the M&P40. 4 failures to fire.
15 rounds through the Glock 22. 0 failures to fire.

So while I might not have been seating the primers deep enough originally, I think I can now rule that out as a possibility for the failures to fire.

RH45 - I have not been measuring my pistol brass before loading it. I do it religiously for 223, but have read in multiple places where it was not necessary in pistol rounds.

With the failures now of both RP brass and Winchester brass, it may be safe to also assume case length is not the problem. Hellifino.

 

[shooter1]

tydephan,
I know these little problems are mind bogglers, but you will work through them. When you mentioned that the primer strikes were slightly off center on your misfired primers, my first thought was the pistol was not completely in battery when the striker released. It's a problem I ran into with a Glock 21 with an aftermarket barrel years ago. The problem was the slight bulge in the case caused by the seated bullet. The rounds chambered and fired fine in my other .45s, including my 1911s. The case bulge prevented the round from fully chambering by a couple thousandths. That's when I discovered the LFCD I mentioned earlier. I changed my loading process to seating and crimping (LFCD) as separate operations. Problem solved. I kept the Glock about 9 years after the change, and shot it a LOT. You may not have the same problem, but it's worth checking out. You have adequate die stations on your 550 to give it a try. If you don't like the LFCD, I believe Dillon makes a final crimp die as well.
Good luck!
str1

 

[tydephan]

Thanks shooter. Let me ask you this - if there was a bulging issue, the rounds wouldn't just drop into the chamber when I test "drop" them into the barrel (separate from the gun of course) would they? Wouldn't there be some slight friction?

Here's an image I took tonight from one of the FTF from this evenings session:

 

[shooter1]

In the Federal Ordinance barrel I had in the 21, the rounds would drop in. There was slight resistance removing the round with a fingernail. Good picture! If the case is in the firing orientation in your chamber, it is slightly low toward the 6 O Clock position. It looks to be pretty light as well. Do the rounds that fire show the same primer strikes? Do you have a stock power striker spring?
str1

 

[shooter1]

I'm doubting you have an ammo problem. Chances are the new striker assembly will cure the problem. I would be interested to know what that problem is. The M&Ps I see at the club seem to be pretty much problem free. Hope the new assembly comes in quickly. I know this is wearing on you! Let us know how it works out.
str1

 

[tydephan]

In the Federal Ordinance barrel I had in the 21, the rounds would drop in. There was slight resistance removing the round with a fingernail.

These drop in and out. I can drop one in and rotate the barrel and they just drop right out without any coercion. I don't think that dismisses the possibility of what you're talking about though.

I doubt the round is oriented in the photos as it was when it was struck. The strikes look maybe very slightly lighter than rounds that have been ignited. Hard to tell on some, and then others very definitely look lighter.

Thanks for the help. We'll wait and see. I'll be sure to update when I have some new results. As for now, this one goes in the safe until the new assembly arrives.

ETA: If the striker assembly doesn't fix the issue, I'll investigate the seating and crimping in different stages option. Thanks a bunch!

 

[kmbrman]

tydephan&shooter1

Another problem I've run into with the M&P is that some out of spec. factory rounds don't chamber or eject well. Some Aguila 9mm I've tried would have to be pushed into the chamber by hand the last smidgen to seat fully. Also the bullets were seated too deep in the case,compared to American made rounds and when the length was measured they were shorter than other rounds of the same grain [115] bullets! This is of course not a fault of the gun.

 

[tydephan]

I have good news! The new striker assembly seems to have fixed the issue. I fired 65 rounds this afternoon after installing the new assembly and experienced 0 failures. Obviously I'll put several more hundred rounds through the gun to make sure.

Check out the differences between the new striker (left) and the old one (right).

I bought this gun used, and I'm almost positive the previous owner has done some sort of milling on the part of the striker exposed from under the slide.

 

[kmbrman]

tydephan

The striker in your photo on the right side of the picture has had it's profile changed by someone doing their own gunsmithing. In Dan Burwell's trigger job info that's on the internet, he tells owners not to change the contact surface on the striker face ,and only to polish and to NEVER remove metal. It should always look just like the new one in your picture. If the profile of the face is changed the firearm could be dangerous and discharge by accident by having the hump that is seen, removed by careless Kitchen Table gunsmithing .

 

[fastbolt]

I was going to say that I'd suspect you have a M&P 40 from the production period before they revised the striker. A change was made to increase the material located on the front of the striker's foot to allow more spring compression and increase the force of the striker's impact.

You posted a good picture of the difference, but since I've already copied them I'll post a couple thumbnails anyway.

The first is of a current production striker laying on an image of the earlier production striker in an earlier armorer manual which allows you to see the difference in between them on the front edge of the foot, and the second image shows the same pictures from the pages of 2 different releases of the M&P armorer manual (which also displays the difference in the striker foot dimensions). Enlarge each of them a couple of times for a bit better detail.

 

[shooter1]

tydephan,
It appears your MP40 did have the earlier striker assembly and/or had been cobbled up. I'm sure your problem is solved! Just keep the striker channel clean and dry and misfires are a thing of the past. GREAT news, enjoy your pistol!!
str1

 

[tydephan]

Curious as to why someone "might" have modified the striker assembly and pickup bar (pictured below), I asked Dan Burwell for his comments.

Below is what he had to say:

Niether of those were done by the owner.

What you have there is a second generation striker. they did not have the extra step. the extra step gets a little more retraction on the striker loading the spring more.

they slide is they way they slides came for awhile. S&W would have the slide melonited then finish the pick up. Don't ask me why.

This is the "modification" I thought was made to the pickup bar:

 

[kmbrman]

Striker difference

Guys , I'm glad we found some interesting facts out about the striker changes to the M&Ps. Mine has the HUMP on it so it's the other design. By the way the M&P can benefit from the new after- market sights from Dawson Precision .I added the staight target version with black on black, with screw click adjustments for windage and elevation. Come in really handy to zero different loads.