M&P FPC information, complete disassembly & replace hammer spring

[marvin02]

The six bolts holding the receiver together are 4-40 by three-quarter inch, Button head. The nuts are nylok, nuts 4-40.


Here is a video:



That channel has a lot of info on the FPC.


If you are going to disassemble the receiver you want to have replacements bolts on hand. The tiny torx heads strip very easily.


Amazon links:


MonsterBolts - #4-40 x 3/4" Button Head Socket Cap Screws, ASME B18.3, Alloy Steel, Black Oxide, 20 Pack

MonsterBolts - #4-40 Nylon Insert Hex Lock Nuts, Alloy Steel, Black Oxide, 25 Pack

Smith & Wesson has revised the firing pin and spring:





I have an early model and have had zero issues but I guess some were having light strike issues.

Edited 5/13/25 to fix links after forum software update.

 

[marvin02]

Hammer Spring Replacement

One of the complaints I hear from people at steel matches who try my FPC is that the trigger is too heavy. Here is a series of videos showing how to lighten the trigger pull:











I have done this to my FPC. Here are my results:


Out of box - 5 lbs, 2 ounces

After 100 rounds - 4 lbs, 8 ounces

After 500 rounds - 4 lbs, 6 ounces

After 1,000 rounds - 4 lbs, 3.4 ounces

After reduced power hammer spring: 3 pounds 5 ounces


So on mine it reduced the pull by 1 pound. Changing the hammer spring didn't effect the reset. It did make it noticeably easier pull the bolt handle back when the hammer was uncocked.


Went to the range today and tested. No light strikes.


BLAZER 124 - 9 rounds ( all I had)

REM UMC 124 - 31 rounds

FIOCCHI 124 - 15 rounds

PPU 124 - 41 rounds

S&B 124 - 20 rounds


Doing a detailed take down on the FPC allowed me to deep clean it. Everything except the barrel went in my sonic cleaner.


Edit: Even if you don't want to change the hammer spring the videos above are a great look at the FPC internals.

Edited 5/13/25 to fix links after forum software update.

 

[marvin02]

M-Carbo now has flat triggers and a trigger spring kit for the FPC:


Smith and Wesson FPC Accessories - M*CARBO


No MCarbo install video though.

Edit: I am not affiliated with either of the YouTube channels linked above. I hope someone gets some useful info from this thread.

 

[marvin02]

Field stripping the FPC:



Edited 5/13/25 to fix links after forum software update.

 

[marvin02]

FPC Bolt Disassembly

How to disassemble the bolt on the FPC:



If you have an early model your bolt may have roll pins (mine does). I have taken my bolt apart and the pins came out with no problem.

Edited 5/13/25 to fix links after forum software update.

 

[marvin02]

Here is another take on detailed disassembly:







Edited 5/13/25 to fix links after forum software update.

 

[JRD]

Bear in mind that in a hammer fired blowback action, cocking force of the hammer helps resist the bolt opening.
By using a lower power hammer spring you are increasing bolt velocity. In engineering, everything is a trade off. To have more of something, you need to give up something else. Here they are trading a lighter trigger pull for some degree of increased recoil and increased wear. The FPC is pretty stout though so maybe it’s fine.
Just understand the trade offs and make an informed decision.

 

[JRD]

Another thing I just noticed. In the Four Peaks Tactical trigger job Part 3 video, at 6:20 he shows reassembly of the bolt catch plunger and spring into the feed ramp block, he installs those parts backwards. The closed end of the plunger should face rearwards to engage the bolt catch. He has the plunger facing forwards.

 

[marvin02]

Another thing I just noticed. In the Four Peaks Tactical trigger job Part 3 video, at 6:20 he shows reassembly of the bolt catch plunger and spring into the feed ramp block, he installs those parts backwards. The closed end of the plunger should face rearwards to engage the bolt catch. He has the plunger facing forwards.

So I've watched Part I and part III and he puts the spring in the same orientation that he took it out.

I've attached screen grabs from both parts. They show that the spring is toward the feed ramp. I know that mine is installed with the spring toward feed ramp.

 

[JRD]

The screen grabs demonstrate my point. The bare end of the spring should face the muzzle. The flat end of the plunger should face rearward to engage the bolt catch.
Regardless of how it was when he first takes the spring out, it was in there backwards.
Maybe it’s a great design and will still work with the plunger installed backwards…

 

[marvin02]

The screen grabs demonstrate my point. The bare end of the spring should face the muzzle. The flat end of the plunger should face rearward to engage the bolt catch.
Regardless of how it was when he first takes the spring out, it was in there backwards.
Maybe it’s a great design and will still work with the plunger installed backwards…

What's your source for this info? I would love an exploded view of the FPC or any other info you have.

 

[JRD]

S&W has not published an exploded view of the FPC so there are no pictures to share.
I've got some friends at the factory who are very familiar with the FPC and confirmed the design intent of the plunger for me.
I know it may sound sketchy that some guy on the internet says he knows someone who knows the answer... but I assure you I'm not inclined to spread any incorrect information on this forum.

 

[marvin02]

S&W has not published an exploded view of the FPC so there are no pictures to share.
I've got some friends at the factory who are very familiar with the FPC and confirmed the design intent of the plunger for me.
I know it may sound sketchy that some guy on the internet says he knows someone who knows the answer... but I assure you I'm not inclined to spread any incorrect information on this forum.

Thanks for the reply. I'm just trying to share what info I can find about the FPC and welcome pointers to any sources that have additional info.

 

[Tom S.]

I like the idea of a flat-face trigger, but dang that's pricey!

 

[marvin02]

I have edited my posts in this thread on 5/13/25 to fix links after forum software update.

I did request a new firing pin, firing pin spring, bolt pins and a spare recoil spring from S&W and they sent them to me free. Took about 4 weeks to receive them.