M&P sear plunger size


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ny32182
July 26, 2012, 10:52 AM
I think the sear spring in my M&P is on the way out, so I am looking for some spares. Things I have observed:

1) Like some other M&P springs, it looks like stock ones are nigh impossible to find on the open market

2) It appears Apex makes at least four versions:

-"Small plunger" competition
-"Small plunger" carry
-"Large plunger" competition
-"Large plunger" carry

My trigger is a fully stock Pro version. Does anyone know if there is a way, without taking it apart and measuring, to know if I have the small or large sear plunger? Does anyone know whether the "carry" or "competition" version is going to be more reliable with the stock Pro sear?

Gun was originally purchased sometime around March 2011 and is a stock 5" 9 Pro. Thanks,

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rsbufo1966
July 26, 2012, 11:39 AM
Could you explain why you think the sear spring is going out? A little more information would be helpful...

Are you experiencing sear flutter/failure to reset?

Was the gun manufactured in 2011, or was that just the purchase date?

How many rounds do you have through it to date?

As for which size spring...you'll have to detail strip the gun, remove the sear from the SHB and eyeball it.

I can't answer as to the reliability of the Apex springs with the Pro sear. I installed the full DCAEK on my 40fs, and it uses the small sear spring. On M&P's with the small sear spring there are reports of sear flutter/failure to reset with the DCAEK, however I've never experienced this. I also have a 40c, and I only installed the Apex USB as I like the pre/post-travel and reset that the stock sear provides for carry purposes.

If you find you have the smaller sear spring, Apex can/will mill your SHB to accept the larger sear spring if you'll contact them...

One final note: Don't install the Apex Comp AEK parts on your carry gun... I can't see any good coming of that if you were to have to use it in self-defense.

ny32182
July 26, 2012, 11:47 AM
Could you explain why you think the sear spring is going out? A little more information would be helpful...

A couple..."bump fire" near-doubles in live fire recently; and a couple "dead trigger" failure to resets in dry fire.

Are you experiencing sear flutter/failure to reset?

Beginning very intermittently now, yes.

Was the gun manufactured in 2011, or was that just the purchase date?

I don't know. It has the newer striker if that helps.

How many rounds do you have through it to date?

A little over 13k live rounds; probably 2-3x that much in dry fire.

As for which size spring...you'll have to detail strip the gun, remove the sear from the SHB and eyeball it.

Ok. I was hoping there was a way to tell based on other details of the internals, etc, but maybe not.

I can't answer as to the reliability of the Apex springs with the Pro sear. I installed the full DCAEK on my 40fs, and it uses the small sear spring. On M&P's with the small sear spring there are reports of sear flutter/failure to reset with the DCAEK, however I've never experienced this. I also have a 40c, and I only installed the Apex USB as I like the pre/post-travel and reset that the stock sear provides for carry purposes.

If you find you have the smaller sear spring, Apex can/will mill your SHB to accept the larger sear spring if you'll contact them...

One final note: Don't install the Apex Comp AEK parts on your carry gun... I can't see any good coming of that if you were to have to use it in self-defense.

It is an SSP/Production competition gun only, but reliability is the top priority; everything else is a distant second.

I would order all four but they are about 7 bucks each, so for $21 I guess I will just take the sear off and mic the plunger.

ATLDave
July 26, 2012, 12:27 PM
Have you tried calling Apex? They may be able to advise.

rsbufo1966
July 26, 2012, 02:05 PM
+1 on calling Apex. You've got enough rounds down range at this point that it wouldn't hurt to just replace all of the springs.


"A People that values its privileges above its principles soon loses both" Dwight D. Eisenhower.

Shoot more, talk less...

ny32182
July 26, 2012, 02:07 PM
I've been able to find spares for everything but the sear plunger spring and magazine catch spring.

fastbolt
July 26, 2012, 02:16 PM
I'd call S&W and let them examine it under their lifetime (to original owner) warranty.

However, at over 13K rounds, you're ready for some spring replacements. Have you done any up to now? Last time I checked, they were recommending LE armorers replace recoil, mag, trigger bar & striker springs at 5K rounds.

The heavier (MA compliant) sear plunger and its spring were incorporated into standard production over a year ago, although the sear assembly has to be disassembled in order to determine which one is in a gun.

Here's a picture of the original (left) and the heavier (right) sear plunger & spring ...

http://i3.photobucket.com/albums/y73/fastbolt/new39219block.jpg
http://i3.photobucket.com/albums/y73/fastbolt/searplungersorivmaandsprings.jpg

The slight "downside" to the heavier plunger & spring is that it seems to add a bit to the trigger pull.

Call the company.

ny32182
July 26, 2012, 02:29 PM
Wow, great pics fastbolt, thanks... no way I am sending this thing to S&W for a spring though, I shoot it every weekend.

I use ISMI 13lb recoil spring and am on my second one of those (going to run up a higher round count on this one just to see what happens), and I've had to change the springs in my three primary mags every 2500 rounds at most. That has actually been kind of disappointing, as my original Glock mag springs went almost 10k rounds on basically the same schedule.

But anyhow. I am on all the original springs except for the recoil and mag springs. I have found spares for everything but the sear plunger and magazine catch. Next time I detail the gun I will probably replace all the originals that I have not done yet; trigger return, extractor spring, sear plunger, etc. except maybe the striker. I use Federal primers in my sanctioned match ammo, which are known for being easy to set off; and I use Tulas in practice that are known to be the hardest on the market, so I will get plenty of advance warning on the striker spring going bad.

ny32182
July 26, 2012, 02:36 PM
I will call Apex and see which they recommend with my sear.

Is there any trick to taking the plunger and spring out once the sear is off, or are they just sitting loose in there?

ny32182
July 26, 2012, 03:24 PM
Apex is going to "talk to the gunsmith and call me back" so we'll see how that goes; I will probably order both weights for whatever plunger size I have, to be determined tonight. Wish I had more time to test but I have a major match in two weeks so it will pretty much have to be right the first time; I will probably either hope the stocker holds out a bit longer or go with the heavy Apex version... unless the stock appears to be weaker than the competition spring.

ny32182
July 26, 2012, 04:13 PM
The Apex lady said that either should be reliable and the only difference should be trigger pull weight. She also thinks I will have the large plunger since my gun is likely produced in 2010 or later.

9mmepiphany
July 26, 2012, 04:31 PM
You can pretty much trust what Lisa tells you...she is a ranked shooter, not a gunsmith...I'm sure she checked with Randy or Scott first.

Either the Comp or Carry plunger spring will be reliable...they wouldn't sell it if it wasn't...it really is just about the perceived weight for the carrier

Is there any trick to taking the plunger and spring out once the sear is off, or are they just sitting loose in there?
Nope no trick, it is just sitting in the hole. You might need a pick to snag the spring out, but the plunger should just drop out when you invert the module. They recommend putting a small dab of lube in the end of the spring, when reinstalling, so that it holds the plunger in place as you put it back in.

ny32182
July 27, 2012, 09:50 AM
Lisa, yes I think that is who I spoke with.

If anyone is curious I have the large plunger.

I cleaned a little gunk from around the sides/under the sear so that should help till I can get/test a new spring. Thanks for the insight guys.

ny32182
August 7, 2012, 01:48 PM
Just wanted to update this for anyone reading later, the new springs came in, but I have not installed either of them yet. I'm about 800 rounds in without any hint of a problem since the cleaning, so maybe that is all it really needed. Assuming this continues I will just replace it with all the other small springs at the end of the year, and make sure to clean under the sear every time I detail the frame in the future.

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