S&W M&P .45 reassembly

josquin

josquin

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A friend who recently bought one of these is having trouble reassembling it (yes, despite reading the instructions.) He rang me up and said, "I'm bringing this over for you to figure out; you know everything," (It's a lie, folks. If I knew everything I wouldn't be posting this question!) I've only handled one of these briefly before and don't know the correct names of the parts, so bear with me.

The problem is that he/we cannot get the slide all the way back to allow the takedown lever to be swung back in place. It appears that the trigger arm is snagging on a spring-loaded pin in the top of the slide, whose function I don't know. The pics show the areas in question:

Slide detail_1613.JPG


Trigger_1612.JPG


From what I can figure of the geometry, the spring-loaded button ought to be depressed by the bevel of the piece on the return stroke, but on the recoil stroke, it seems the trigger arm may move slightly outward and allow the pin in the slide to pass. A very small jeweller's screwdriver can be used to hold the trigger arm to one side while the slide is being brought back, but of course that is not the procedure one is expected to use!

There is obviously a simple explanation for this. Perhaps someone who is familiar with this pistol can enlighten us?

:) Stuart
 
The button is normal and is supposed to protrude.
The 2nd picture, the "arm" seems to be offset a bit. When my M&P40 is apart, that arm should be resting on the frame. There is a take down lever in the magazine well, make sure it is lowered, this controls that "arm" in your lower pic. It moves left to right. To me your lever is raised.
 
In my M&P the trigger arm (second pic) seems to go right to the side of the frame, yours seems to have about an 1/8" gap. At first I thought that the safety arm (the silver bar that contacts the mag an allows the trigger arm to contact the sear) was out of place and allowing the arm to move towards the sear, and get out of place. this would cause it to contact the silver pin on the slide.

Firstly I would apply gentel pressure to the Mag saftey (the silver arm beside the green arm you have to push down before you do a takedown) this little bugger has a arm on it that contacts the trigger arm and allows it to come in line with the sear when there is a mag in place. Use a punch or a small screw driver to operate the "silver arm" up to see if you have propper operation. The "curled" piece on the side of the trigger arm should only line up with the sear when that saftey is in the "up" possition.

On my M&P I can move the trigger arm a little bit side to side, if this is the case on your buddies M&P just use a long punch or small screwdriver to hold the trigger arm to the side of the frame through the magwell as you slide the slide back in place, (go from underneath) and then it should go back into place.

I have also had a little bit of build-up in my M&P when using dirty ammo, just check to see if there is an carbon or fouling in the spring mechanism that operates the trigger arm or mag saftey, if there is clean it up with some solvent or Gun Scrubber.

If you do all of these things and you still get "No joy" I would have to say you need to take it somewhere, this may be a warranty issue. You may want to check that out First.

Good lucK, hope this helps......
 
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The 2nd picture, the "arm" seems to be offset a bit. When my M&P40 is apart, that arm should be resting on the frame. There is a take down lever in the magazine well, make sure it is lowered, this controls that "arm" in your lower pic. It moves left to right. To me your lever is raised.
Click to expand...

At first I thought that the safety arm (the silver bar that contacts the mag and allows the trigger arm to contact the sear) ...
Click to expand...

I suspected that the trigger arm should be resting against the frame. The "take down lever" referred to is , I think, "the sear deactivation lever" and yes, it was raised when I took the pic but I have been making sure it's lowered when I try to reassemble. Here's a better pic of the action:

Action_1616.JPG


Firstly I would apply gentel pressure to the Mag saftey (the silver arm beside the green arm you have to push down before you do a takedown) this little bugger has a arm on it that contacts the trigger arm and allows it to come in line with the sear when there is a mag in place.
Click to expand...

OK- you lost me there. :( With the sear deactivation lever down, the trigger arm does not move laterally when I insert a magazine, which I suspect it ought to. If that is the case, it looks as if the sear deactivation lever, when it flips up on inserting a mag., ought to bear against the round bit ("???" in the pic) between it and the trigger arm, thus pushing it and the trigger arm aside. But that round bit is attached to the trigger arm and extends under the sear.

Hmmm... the more I look at this, the more I like my 1911... :p

:) Stuart
 
Try pressing in on the firing pin safety (the round thing on the slide) while pulling back on the striker. Then release the firing pin safety, then the striker. The 45 doesn't have a mag safety (well, most of the ones in Canada don't,) so it's normal that the mag safety arm isn't there.
If you want/need to know more about the M&P pm me your email, I've got a couple of things that'll help out (parts diagrams and a write up on a full teardown with pictures).

ETA: ???? is the sear activation lever (the dohickey that tilts the sear to release the striker)
 
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notsorichguy said:
In my M&P the trigger arm (second pic) seems to go right to the side of the frame, yours seems to have about an 1/8" gap....
Click to expand...

I think I'm getting a better picture of how this thing works- maybe. I thought perhaps that the trigger arm ought to be flush against the frame but I now see that it must have some lateral movement because the sear activation lever (marked "???" in my last pic) would otherwise not be able contact the sear and release the striker.

So the question appears to be: How does the firing pin safety (in the slide) push the trigger arm out of the way? The trigger arm must be in the "return" position (as in my pic) in order to fire the gun. I thought there might be some peening of the trigger arm extension where it meets the firing pin safety if it's been out of alignment but this seems not to be the case. (I"m not sure if my buddy has fired the gun since discovering this problem- I think not.) I would expect the inside surface of the trigger arm extension to be bevelled to allow it to be pushed out of the way as the FP safety goes past but there is no bevel.

Update: My friend fired about 100 rounds yesterday with no issues. I discovered that by pulling the trigger back and "fiddling" a little, it is possible to get the slide back in place, so it seems that - perhaps because the gun is new - a little wearing-in is needed. I guess I could very gently bevel the edge of the trigger arm extension where it contacts the FP safety, but perhaps we should just see what transpires naturally.


:) Stuart
 
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josquin said:
I think I'm getting a better picture of how this thing works- maybe. I thought perhaps that the trigger arm ought to be flush against the frame but I now see that it must have some lateral movement because the sear activation lever (marked "???" in my last pic) would otherwise not be able contact the sear and release the striker.

So the question appears to be: How does the firing pin safety (in the slide) push the trigger arm out of the way? The trigger arm must be in the "return" position (as in my pic) in order to fire the gun. I thought there might be some peening of the trigger arm extension where it meets the firing pin safety if it's been out of alignment but this seems not to be the case. (I"m not sure if my buddy has fired the gun since discovering this problem- I think not.) I would expect the inside surface of the trigger arm extension to be bevelled to allow it to be pushed out of the way as the FP safety goes past but there is no bevel.

:) Stuart
Click to expand...

The trigger bar only lies flush to the frame for the M&Ps with the mag safety. For those of you with the mag safety, you'll notice that if you push the mag safety bar up (as if a magazine were inserted), the trigger bar will move toward the centre just like in OP's second pic. So that explains the gap.

As far as the firing pin safety goes, it works opposite to the way you describe. The circular firing pin safety in the slide doesn't push the trigger bar protrusion out of the way, it's the other way around. As the trigger is pulled, the rear surface of the protrusion (tilted at roughly a 45 degree angle) contacts and pushes the firing pin safety up and lets the firing pin travel.
 
tritium4ever said:
...As far as the firing pin safety goes, it works opposite to the way you describe. The circular firing pin safety in the slide doesn't push the trigger bar protrusion out of the way, it's the other way around. As the trigger is pulled, the rear surface of the protrusion (tilted at roughly a 45 degree angle) contacts and pushes the firing pin safety up and lets the firing pin travel.
Click to expand...

Thanks for the clarification. I did end up stoning the trigger bar protrusion very gingerly and it now requires a little less fiddling to get the slide back. But it's quite manageable.

My friend is a happy camper again and I've learned a lot - thanks to the Open University at CGN.

:) Stuart
 
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