I have recently purchased an M&P 357 sig compact. I was polishing the sear and trigger bar this afternoon and ran into a problem. After putting it all back together and trying out the trigger pull, after a half dozen pulls it quit releasing the sear. After examining and studying it for a while the trigger bar was shifting to the right and not staying under the sear allowing it to release the striker. I looked around the work bench and found two pieces of clear tubing. This pistol has the older style sear housing, black, not the silver one with the larger sear spring and plunger. It appeared to me that one of the tubes is used to keep the trigger bar from sliding to the right. Has anyone experienced this situation before?

Your help would be appreciated.

Spark1954

OK after thinking about this for a few days, I now remember where the plastic tubes came from, some new tweezers I got out to assist in replacing the sear springs if they were to fall out of the sear block. Now for the REAL problem, the trigger bar wants to shift to the right as the trigger is pulled back, shifting it away from the sear. I took it to the local shooting range today to adjust the sights as it was shooting to the left at 15 yards and it performed flawlessly, even with the small piece of tubing in the sear block. Is there a way to correct this situation so that the trigger bar does not shift? Also, because of the high price of 357 sig ammo, I am considering purchasing a 40 caliber barrel to install. I have found two brands of barrels, Storm Lake and factory S&W, are there others and is there a difference in the accuracy of these two barrels? Also will I need a different recoil spring as well to allow use of the 40 cal barrel?


TIA

Sparks1954

Sparks:

I'm not sure about the sear issue - if the trigger spring is set up right, things should work. But it's possible to put things back together wrong.... The tip of the trigger bar may bent somehow....

Seems like the consensus is to use the Storm Lake barrel to make a 9mm out of a .40, because the stock S&W barrel is designed around a smaller breech face arrangement, but Storm Lake is selling a "conversion" barrel.

However, the .357 Sig and .40S&W breech face is the same, so I'd go with price - I don't think it'll matter for other than absolute accuracy issues.

Since these are SD guns, getting six rounds into a 6" circle is about what we need, and the barrel choice shouldn't matter.

S&W is apparently using the same recoil spring across all the M&P versions of the same length, if not entirely.... (I'm quoting somebody .) I wouldn't worry about it.

Regards,

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Stu.

Did you completely remove the trigger bar from the frame?

If so, did you recapture the trigger return spring (with the pin) when reinstalling the trigger? Did you install the spring in the correct orientation? Is the rear of the spring hooked within the hole of the trigger bar? (The "open" coil connects to the trigger bar with the opening of the coil facing upward.)

Capturing the front of the trigger return spring with the pin is mostly easily done using an assembly pin, and making sure the front coil is properly centered and not displaced off to one side as the real pin is installed.

The trigger return spring exerts tension to help pull the rear of the tail to the left (and under the sear). If it's been incorrectly installed at either end (and if the coil was dropped by the bar's hook because the opening was at the bottom and it was dropped off the bar while the bar was being positioned inside the frame to be reinstalled), you may have lost tension at the rear of the bar's tail.

Does your model have a magazine safety? If it does, and you removed the small dog-leg spring, you might have a problem where the lever isn't being rotated as it should and the tail is being held away from the sear nose.

If you damaged/tweaked/bent the tail while "modifying" the trigger bar? Well, that's another matter.

Dunno. Just some thoughts. You can't "diagnose" what's wrong with a firearm online, you know. I'd have to be holding it and examining it in order to diagnose what might be wrong. Sorry.

__________________
Ret LE Firearms inst & armorer

Well I worked on the pistol some more today, the trigger bar will to shift to the right away from the sear without some type of support to keep it aligned. I have removed the peice of rubber hose, (what was I thinking) and replaced it with a small peice of brass that I trimmed to fit snugly into the channel that the tail rides in. This keeps it in line with the sear just perfectly. Until today I had not fooled with the trigger group. I removed it to try to determine if some thing was out of alignment. All was in order, and since I had it apart I decided to examine the trigger return spring. I measured the diameter of the spring wire and see if I had some smaller diameter spring in my stash. I measured the spring at .0025 and I had a spring on hand with a diameter of .0023. I cut the spring to length and installed it, what a difference it made in the trigger weight. Now I am very pleased with the trigger.


Thanks for your assistance and advise.

Sparks1954

there is something wrong. you cannot trim the trigger return spring as there are loops that hook to the pin and trigger bar. Did you trim the spring under the sear??

from what you describe, I would think its the trigger return spring.

here is a pix of the part. the trigger return spring has the loops on each end

https://apextactical.com/store/avact...eb-600x400.jpg

I don't know what you're doing to your M&P pistol.

A piece of brass - replacing a piece of rubber hose - in the sear housing at the tail of the trigger bar?!?!

Yes, it sounds like something is now wrong with your M&P.

The trigger bar has a slight inward (leftward) bend along its length, which, in addition to the tension exerted by the trigger return spring, helps keep it under the nose of the sear. If you've bent the trigger bar, it's time for a new one.

Perhaps it would be prudent to return your pistol to its original condition, with new stock parts replacing whatever it is you've modified. Why not simply shoot the pistol in stock condition to let the parts wear in on their own? The trigger bar vertical extension will wear against the bottom of the slide (especially since the slide is pretty hard, with the surface being Melonited) and the sear nose will wear in against the trigger bar's angled cam ramp.

Yes, I know some guys who have installed some of the Apex parts, and I've helped some of them, but making sure the normal safety and operation of the gun wasn't compromised was always a priority.

There's an old saying that some folks aren't happy with something until they "fix it" till it's broken ...

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Ret LE Firearms inst & armorer

"there is something wrong. you cannot trim the trigger return spring as there are loops that hook to the pin and trigger bar.


Well you can trim the trigger return spring, although that thought never entered my mind. I want to keep the stock parts stock so that I can return it to stock if I need to in the future. But you can replace the spring with some careful measuring and prudent installation and forming. I replaced the spring with a spring of lesser diameter, smaller wire. The loop structure as well as the number if coils remain the same and it is installed in the same manner. What I accomplished was a lightened trigger pull without modifying the sear spring, sear angle or trigger bar in any manner. It did not seem logicial to allow the trigger bar to flop from side to side so the shim in the trigger "tail" channel will prevent this from happening. I agree that the rubber hose was a stupid idea, shame on me. I figured out a better solution.

I feel confidant and safe about the end result.

Sparks 1954

FB:

Long time no see....

Nothing much new here except that we moved in with mom to help take care of her, and then she decided to Winter in El Paso last Thanksgiving, and hasn't bothered to come back yet .... She spends her days with at least one dog (my sister has six) on her lap. (We inherited my daughter's two cats, which Sammy the dog didn't entirely approve, but my sister is the loser - my daughter moved in with her .)

Anyway, sure sounds like Sparks has bent the tip of the trigger bar, or the loop. (Or the whole bar?) The bar being where it's supposed to be is almost magic anyway, and there's nothing to keep it in place except the Apex RAM kit. (Well, almost.) If there's a bend in there, though, it's going to be "off".... (The RAM might help a little here.)

I thought I'd managed to put my trigger bar in wrong at least once, but that has more to do with getting the sear block back into the gun than anything else.

I vote for a bad trigger bar at this point....

Sparks:

FWIW, Fastbolt really knows these guns. I've been pestering him for years ....

Regards,

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Stu.

Hey, glad to hear things are working out okay for your family. Yeah, it's been a while since we came across each other here & there. Now that I'm feeling better I've been busy and am starting to get back out in circulation again.

Catch you later.

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Ret LE Firearms inst & armorer

The bar being where it's supposed to be is almost magic anyway, and there's nothing to keep it in place except the Apex RAM kit.

I studied the function of the Apex RAM kit and with your very patient advise, I now understand how this is trigger/trigger bar/sear assembly works. I was under the mistaken theory that the trigger bar was to lift the sear and keep it lifted. This will not allow the sear to reset to allow the striker to be reset for the next pull of the trigger. It is a very fine balancing act for the sear to be lifted, the trigger bar to shift to the right out from under the sear and allowing the sear to capture the striker while the slide is moving forward, for the next shot/pull of the trigger. Not nearly as simple as it seems at first glance. Fastbolt, I took your advice and returned the pistol to stock configuration, removed the lighter trigger return spring, and replace the polished sear with a stock one and "Lo and Behold" it functions as designed. I guess if I want to improve the trigger I will order an Apex DCAEK, unless y'all don't recommend this. The APEX RAM in its current offering will not fit the M&P with a thumb safety sear block.

I Really appreciate your patience in this endeavor.

Sparks1954