M&P trigger terminology please

[bobermo]

I'm new to firearms. Recently purchased a 9 Pro. My trigger felt "gritty" to me, although I don't have any other striker fire pistols for comparison.

Can someone explain trigger terminology for the M&P striker fire system.

Specifically:

1. when the trigger lever first contacts the blocker
2. as the trigger lever pushes up on the blocker
3. when trigger lever first contacts the sear
4. when the sear and hammer disengage

It seems like all my grittiness is definitely coming from when the lever contacts the blocker, as my trigger is silky smooth with the slide off and sear engaged.

According to the shape of the lever tab that contacts the blocker, I get very distinguished "steps" upon trigger pull before firing. I believe this is due to the angles in the lever tab and geometry of the blocker. It seems if these areas of contact were more rounded, rather than angled, the pull would be more even without the steps. Are the steps desired by shooters?

I plan to install a Apex USB and do some slight polishing of the lever tab where it contacts the blocker. I definitely feel some rough spots with my fingernail on the lever tab that I believe are contributing to the "gritty" trigger.

I know the trigger has been discussed greatly here. I'm mainly asking for some terminology and whether the "steps" are acceptable and/or desired. Thanks.

 

[jajo]

If the feel is unacceptable to you, then I suggest installing the Apex USB first. Try this before polishing any parts. This simple swap of parts made my trigger pull very smooth.

On the other hand, some people have stated that as their pistol was broken in, the trigger pull got smoother when the components naturally burnished each other.




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[WR Moore]

When you say "blocker", I expect you refer to the striker safety plunger.

Now then, with the slide removed, the trigger actually isn't doing anything except moving the trigger bar (which I believe you're calling the 'trigger lever'), it's not moving any other parts of the firing mechanism, so of course, it's effortless. If your pistol lacks the magazine disconnector (and the sear disconnector lever is in the firing position), the trigger bar will move the sear, but the sear isn't under load. Again, there is no effort.

Now then, as the tigger pivots, the trigger bar first encounters the safety plunger, which it then cams upward to allow the striker to move. A different part of the trigger bar then contacts the camming surface on the sear, which it moves until the striker releases. The striker releases when the sear rotates until it loses contact with that portion of the striker that it contacts. This is the "leg" that sticks downward from the slide when you look at the bottom of the slide if it's off the frame.

I wouldn't either worry about or attempt to change angles on various contact surfaces, or the timing of various stages of mechanical action. S&W paid a team of engineers a slew of money to develop the device so that the pistol works both safely and properly. With all due respect, I suggest they know more than you do about such things.

It's not unusual to have minor toolmarks and burrs affect the trigger action on a new pistol. I'd suggest 200-500 rounds to smooth out the artifacts of the manufacturing process before you start swaping parts around. Very limited, gentle deburring of certain contact surfaces may speed this process. Without specific knowledge of your skills and abilities, I can't recommend it.

 

[Bikemobile]

The trigger bar is stamped metal and has a rough top edge when new. Using an abrasive block you can round the back edgea bit to help the break in process. The bar on my 9mm shield had a noticable burr there when i got it.

 

[Rastoff]

The proper name of the part we're talking about is the Striker Block. Here is a pic of the S&W striker block on the left and the Apex Ultimate Striker Block(USB) on the right: (pic from re-gun.com)

As you can see, the Apex USB is much more rounded. This makes for a much smoother trigger pull.

Be careful when you start to smooth or grind on parts of the trigger mechanism. It's possible to throw off the timing of all the parts which may cause your gun to malfunction.

Here is the trigger bar: (pic from G&R Tactical)

The red part is what pushes the striker block out of the way. Take too much off and the block won't be moved at the right time or far enough and the gun won't fire.

 

[Jamie]

If I'm not mistaken, there is/was a thread on removing the striker block and 'cleaning up' the channel it rides in. Required the removal of the rear sight I think. Seems that there might be a rough surface or two in the channel causing the striker block to 'catch' while being moved up into position.

 

[Raptor73]

Excellent thread and great explanation of the relevant parts. Highly educational. Thank you!

 

[robkarrob]

Video on gritty trigger and what I did to fix it.

Bob


M&P Pistol Gritty Trigger Pull -- Striker Blocker Fix - YouTube

 

[howard829]

Video on gritty trigger and what I did to fix it.

Bob


M&P Pistol Gritty Trigger Pull -- Striker Blocker Fix - YouTube

Bob, great video...thanks!

I have a new M&P 9mm FS for about a week now and I have the "Gritty Trigger" as many others have talked about on here. I am wondering when others are replacing the trigger parts surrounding this problem, are they just dropping in the parts and away goes the "gritty trigger?" If as you suggest in your video there could be burrs in the bore then the gritty feeling will still exist, right? I don't feel comfortable with my skills to disassemble and do what you've done to hopefully correct this feel. I have contacted S&W about this and the answer I got was "it should go away" after 500-1000 rounds fired. Is this true? I know if I'm not satisfied with how the trigger feels, I could pay a professional or try to convince S&W to make it right.

I feel the technology and planning that went into producing the M&P should be right on and the customer shouldn't have to pay or replace parts. Maybe it's just a subjective thing between different people and eventually the gritty problem will go away or you might just get used to it and not notice it any longer. I will continue to shoot and enjoy my M&P 9 until I make up my mind what to do, if anything.

Howard

 

[str8liner]

If I'm not mistaken, there is/was a thread on removing the striker block and 'cleaning up' the channel it rides in. Required the removal of the rear sight I think. Seems that there might be a rough surface or two in the channel causing the striker block to 'catch' while being moved up into position.

Thats what I had to do with my shield. The striker block bore had rough edges in it that were catching the striker block.

I radiused the top of the striker block, polished it and the trigger bar, polished the sear striker engagement area and the striker. Made the cut on the front of sear that reduces the over travel.

It made a huge difference in pull weight and over travel.