Is early unlocking still a problem with the FS 9mm M&Ps? RANGE UPDATE

[Nakanokalronin]

Reading a response from my range report on another forum has someone mentioning early unlocking on the FS 9mm M&Ps. After doing a Google search, it seems many have gone with a Wolff guide rod and 20lb recoil spring to fix it which results in better accuracy. My M&P FS 9mm shot fine for me although I believe the groups could have been tighter than what they where so I'm not sure if this is still something that happens.

Anyone change out the recoil springs and guide rod with the type from Wolff and see their accuracy increase?

 

[TxM&P9]

I've read about that too. I thought they were for the older model M&P9 fs.

 

[Nakanokalronin]

I've read about that too. I thought they were for the older model M&P9 fs.

That's what I'm wondering. My groups where pretty good and should be even better now that I have the lighter pull,reset and break point due to the Apex sear. Once in awhile I did get a flyer so I'm just wondering if it still occurs in the current models.

 

[TxM&P9]

yeah, from what I could tell my groups are dead on. I'm not expert on barrel lock up but it seems pretty damn solid from when I rack the slide. Hopefully someone that knows will chime in.

btw. I'll take some pictures on my next outing with my compact an full size to share with yah.

John

 

[1sailor]

So as I understand it, the early unlocking was causing vertical stringing of the groups. And by increasing the recoil spring strength it allowed the gun to remain locked up longer allowing the bullet to leave the barrel before the slide would start back. Is that right? If this was a known problem has it been corrected?

 

[Nakanokalronin]

So as I understand it, the early unlocking was causing vertical stringing of the groups. And by increasing the recoil spring strength it allowed the gun to remain locked up longer allowing the bullet to leave the barrel before the slide would start back. Is that right? If this was a known problem has it been corrected?

That's the reason for the heavier recoil spring I believe. I hope someone on here knows if this has been corrected or not. Hopefully the thrown shots was due to the trigger pull which is where the Apex sear may prove it's worth.

The early unlocking seems to not have been in the .40S&W and 45ACP offerings, just the 9mm.

 

[TxM&P9]

I replied to you on glocktalk. It is a gun problem.

 

[clcdawg]

I have read about this issue before but my M&P is more accurate than I am. Since I shoot it better than a G19 I am not to worried about it anyway.

 

[Nakanokalronin]

I had a few off the wall fliers but it might have been more about the trigger than any barrel issues. After dropping in the Apex sear, the trigger travel is shorter and smoother, reset is shorter and more noticeable and the pull is lighter by at least a pound.

I'll try and get to the range again soon to see how things go, but so far so good. The most accurate ammo out of my FS M&P was the 124gr.+P PDX-1 which kind of surprised me since it's less accurate in my other 9mm offerings. This makes me think I don't have the premature unlocking syndrome but I'd like to be aware if anyone else notices it or if S&W has said anything about it.

 

[MichiganScott]

The relieved firing pin hole in the breech of the M&P would suggest that S&W is well aware of how the pistol unlocks. I suspect any premature unlocking was a trade off for 100% functioning. These are combat pistols, not target guns.

 

[Badkarma 1]

One way to check if your getting a premature unlocking is to inspect the spent casing. Look at the primer, see if there's a vertical mark left by the firing pin. Then it's unlocking early!
You gotta remember the M&P was designed as a .40 first, 9 second, and unlike vicea versa (where the early .40s were actually modified 9mms), Smith had to "detune" the pistol for the lighter 9mm.
Personally though I'd like to know how there running with a 20lb spring though?! Dale

 

[WR Moore]

I'd like to see documentation of a "problem" rather than someones opinion as to why they shoot poorly. Preferably citing measured times for various designs to unlock for comparison. There was considerable engineering work on the M&P series and as someone noted, it was originally designed as a .40 S&W.

Very short version: development of the .40 S&W cartridge required design changes to increase the dwell time-the time the barrel & slide remain locked together-in existing pistol designs. Since the M&P9 shares the recoil spring, locking block and barrel cam designs of the M&P40 (has a very slightly lighter slide) it pretty much has the same dwell time.

In a great many pistol designs based upon the classic Browning systems (like the M&P), the barrel & slide remain locked together as the slide moves rearward in recoil until the cam on the bottom of the barrel meets the cam on the locking block. At that time, rear of the barrel is pulled straight down. to unlock from the slide.

Any protrusion of the primer due to cratering or expansion into the firing pin/striker hole will result in the protrusion being shaved off. In extreme cases, it can lock the barrel and slide together like a pin in a socket. The tear drop relief at the bottom of the M&P striker hole is meant to provide a camming surface for any primer protrusion to prevent malfunction and minimize metal shavings in the firing pin tunnnel which may result in misfires. So, "strange" appearance of the primer compared to a hammer fired design with a different breech face doesn't prove anything either. (S&W also thoughtfully provided a debris drain so that the action of the striker shovels metal shavings and powder residue out of the firing pin tunnel. It isn't mentioned in the manual for some strange reason, cleaning it along with the striker tunnel is a real good idea.)

Most striker fired designs show some signs of striker drag. Recall that the inertial firing pins common to hammer fired designs are spring loaded to move to the rear. Striker fired designs are spring loaded to drive the striker forward so that they can fire. Yes, there may be a retraction spring, but it's nowhere near as strong as the preload spring on an inertial firing pin or the strikers firing spring. Comparing primer marks between the two different designs doesn't demonstrate anything but the difference between the two designs. You certainly can't use it as a method to diagnose 'premature unlocking'.

Walk around a range and look at some primers from competing pistol designs. Glock typically produces a coffin shaped primer mark showing where the primer expanded into the rectangular striker hole. Striker drag marks are also common.

About heavy recoil springs- I don't have figures on the M&P design, but the 1911 with the standard 16 lb spring had slide impact loading of about 700 Gs in recoil and 750 Gs going into battery while stripping a round. Recall that the forces going into battery are being stopped by the take down lever. And you want to increase the load on the take down lever????????????? 20 lb and up recoil springs had a surge in popularity in IPSC back when. Sheared barrel underlugs and slide assemblies launched downrange had a similar surge.

Those who suggest their technique may be the root of bad groups probably have the best grasp of the situation.

 

[Blue'87GT]

One way to check if your getting a premature unlocking is to inspect the spent casing. Look at the primer, see if there's a vertical mark left by the firing pin. Then it's unlocking early!
You gotta remember the M&P was designed as a .40 first, 9 second, and unlike vicea versa (where the early .40s were actually modified 9mms), Smith had to "detune" the pistol for the lighter 9mm.
Personally though I'd like to know how there running with a 20lb spring though?! Dale

FWIW, my .40 full size showed signs of this verticle marking on the primer with the few rounds (~150 rounds) I shot prior to returning overseas. (I only got to shoot for one day--it's in storage for the next year) It was still more accurate than I was. Is this something that I should return it to S&W for? BTW, this was with Winchester white box ammo.

 

[Nakanokalronin]

One way to check if your getting a premature unlocking is to inspect the spent casing. Look at the primer, see if there's a vertical mark left by the firing pin. Then it's unlocking early!
You gotta remember the M&P was designed as a .40 first, 9 second, and unlike vicea versa (where the early .40s were actually modified 9mms), Smith had to "detune" the pistol for the lighter 9mm.
Personally though I'd like to know how there running with a 20lb spring though?! Dale

Here's four cases from my first range trip....

 

[WR Moore]

Blue '87GT- Take a real good look at your breechface when you get back. I expect your primers are entirely normal for an M&P. Fired primers in the M&P are not going to look like fired primers from your M4, M9 or anything else that's hammer fired.

Thanks for your service and watch your 6.

Nakanokaironin-your pictures won't load, at least with my current settings.

From previous post:Most striker fired designs show some signs of striker drag. Recall that the inertial firing pins common to hammer fired designs are spring loaded to move to the rear. Striker fired designs are spring loaded to drive the striker forward so that they can fire. Yes, there may be a retraction spring, but it's nowhere near as strong as the preload spring on an inertial firing pin or the strikers firing spring. Comparing primer marks between the two different designs doesn't demonstrate anything but the difference between the two designs. You certainly can't use it as a method to diagnose 'premature unlocking'.

 

[Blue'87GT]

Blue '87GT- Take a real good look at your breechface when you get back. I expect your primers are entirely normal for an M&P. Fired primers in the M&P are not going to look like fired primers from your M4, M9 or anything else that's hammer fired.

Thanks for your service and watch your 6.

WR-Good point, I'll give it a look when I'm home next. Can't wait to have it in my hands again! Thanks for the last line--will do!

 

[Nakanokalronin]

Blue '87GT- Take a real good look at your breechface when you get back. I expect your primers are entirely normal for an M&P. Fired primers in the M&P are not going to look like fired primers from your M4, M9 or anything else that's hammer fired.

Thanks for your service and watch your 6.

Nakanokaironin-your pictures won't load, at least with my current settings.

From previous post:Most striker fired designs show some signs of striker drag. Recall that the inertial firing pins common to hammer fired designs are spring loaded to move to the rear. Striker fired designs are spring loaded to drive the striker forward so that they can fire. Yes, there may be a retraction spring, but it's nowhere near as strong as the preload spring on an inertial firing pin or the strikers firing spring. Comparing primer marks between the two different designs doesn't demonstrate anything but the difference between the two designs. You certainly can't use it as a method to diagnose 'premature unlocking'.

Shows up fine but try coping and pasting this link in your browser: http://desmond.imageshack.us/Himg708/scaled.php?server=708&filename=dsc01819c.jpg&res=landing

 

[Nakanokalronin]

Are the pictures of the cases showing up for anyone?

 

[Aahzz]

I see the pics fine.

 

[WR Moore]

OK, got home and used another computer. Those are entirely normal primers from the M&P. We adopted the M&P in early 2006, I transitioned to the weapon in April and picked up my personally purchased one in June(?). I'm also an instructor, I expect I've seen ~600K rounds go down range since then with our .40s. Less with my 9 since I'm buying the ammo.

As noted previously, look at your breechface. I've seen empties fired in M9s that didn't look that much different. If you're basing your expectations on .45 ACP empties, remember the 9 & .40 operate at over twice that pressure. Then there's the difference in firing mechanisms.