I picked up my M&P .40 FS from the gunsmith this evening. He installed the Polymer Forward Set Sear and Trigger Kit for $40. The trigger feels unbelievable. Can't wait to shoot it on Saturday. But.. I think something isn't quite right with the striker block. When I dis-assembled the slide to checkout the new striker block, I noticed it didn't appear to be fully out. I pressed on the striker assemble and it was able to move forward without pushing down on the striker block. if I flicked the striker assembly forward so it would snap back, the striker block then held the striker assembly from moving forward until I did push on the striker block. If I just let go of the block, the striker assembly could move forward again when it shouldn't have been able to.

When I performed this same procedure on my .40c with the factory striker block, the striker assembly was blocked every time unless I held the block in.

I looked at the parts the gunsmith took out and I have attached a picture of the SB Spring he took out. This spring is a dark color where all the pictures I have seen show the new spring as bright silver. Does anyone know if the new spring is stiffer than the factory spring or less stiff? I suppose the rear sight should be removed and the spring checked to make sure it is in the striker block correctly and that the little disc on top is attached correctly. I will try to talk to Randy at Apex tomorrow and get his opinion. If I take it back to the gunsmith, it will probably be another two weeks before he can get at it.

Attached Images

IMG_20131114_213713.jpg (40.6 KB, 142 views)

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M&P 40c; 40 FS; 40 Sh; 15 TS

Because your gun is defective after he did the work, he should move you to the front of the line. I'm not saying he will, but he should.

The striker block should move freely when you press it. Does yours bind as you move it? It's possible that the striker block spring was not installed properly and could cause the issue you're having.

Where do you live? If you're anywhere near me I'll fix it for you for free.

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Freedom isn't free.

Thanks for the offer Rastoff. I live in northern Minnesota. I just got a sight pusher after I took the gun to the gunsmith. I will probably take it apart myself now.

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M&P 40c; 40 FS; 40 Sh; 15 TS

HP40cMN:

The rear sight on the .40's (I've got a 40C and 40FS) is pretty easy to move. The problem is in getting the little metal disk in place, over the drop safety plunger spring, without messing up. One good way to muck things up is to forget the disk entirely. That can get the spring bent over the edge of the hole, or other fun things.

It's also possible to get some crud into the plunger tube, or to raise a burr or two while handling it (either on the plunger itself or the tube), and those can mess up things, too.

IAC, you do need to be aware of that little disk, and that the spring may decided to fly away. Been there.... (I managed to shoot the rear sight off of the slide on a Para 1911, and didn't think about the drop safety plunger spring. Never did find the spring, but they're cheap ....) Getting the sight off should be reasonably easy with a decent pusher. (The Shield seems to have it's rear sight installed by the Samsonite Gorilla - same thing that Kimber uses - and it's a bear to get those off. S&W advises to not try it. YMMV, but all three of my M&P's were no problem. The front sight on the 40C was, OTOH, a real bear. Actually, the stock sight was merely difficult. The XS "big dot" replacement front sight was a workout....)

Push comes to shove, S&W probably would give you a "will call" for the gun if you can't sort it out. Or your local gun pusher might be induced to ship it for you ($50-ish, but thirty bucks or more cheaper than FedEx or UPS). The major advantage to the local dealer is somebody to receive the gun when it comes back. No fun to arrive home and find a sticker on your mailbox to the effect that you can have 'em try to drop it off again on Monday.

Regards,

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Stu.

Wait it isn't quite clear to me how you are testing the blocker. But it sounds like it is doing its job...

The test procedure should be as follows.

Field strip
Pull striker back and release, blocker should stop it.
Depress block and striker should continue forward
Striker should remain moveable until pulled back again past the blocker

With the m&p line you can't have a round in the chamber and decocked striker so the free movement before cocking the gun is ok and part of the design.

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[QUOTE=Rastoff;137539705]Because your gun is defective after he did the work, he should move you to the front of the line. I'm not saying he will, but he should.

QUOTE]

It sounds like if there's a problem, it's on the gunsmith. If you tinker with it, all bets are off.

To ItsGotMyBack, when I strip my .40c and test the striker block, the striker assembly can't move forward until I press on the striker block. When I release the striker block, the striker assembly is again stopped from moving forward. I don't have to do any type of cocking of the striker assembly. Doing this same procedure on the .40FS, once the striker assembly moves back and the striker block is allowed to come out, it isn't stopping the striker assembly from going forward again. Watching the youtube video of Randy doing the install at Apex, his testing of the new striker block seems to show the striker assembly not moving forward until the striker block is pushed. Once the striker block is released, the striker assembly won't go forward but he doesn't appear to any cocking motion of the striker assembly. This is why I think there is a problem.

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M&P 40c; 40 FS; 40 Sh; 15 TS

Got it. Blocker isn't blocking. Yeah take it back to the smith somethin' ain't right!

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Quick Update. Took my .40FS back to the gunsmith. He saw what I was talking about and said he noticed it when putting it back together. I had him put back the old striker block and spring so we could check how that worked. Guess what, it reacted the same way. I had him put the new striker block and spring back in. I am going to call Randy at Apex and get his thoughts. I will post back when I know more.

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M&P 40c; 40 FS; 40 Sh; 15 TS

If it does this with either striker block, I would suspect there is a burr (or piece of debris) in the striker block channel causing the block to hang up and not return to it's rest position (or something is causing the striker not to return all the way back preventing the block from popping back. There's not a lot of "slop" in the striker movement forward. I can't move any of mine any distance forward until the block is pushed down (I checked both stock and Apex equipped pistols).

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Minimize the variables

Update #2. I called Apex and talked to tech support. They said they have seen this with a number of different M&P's. They said as long as the striker block pops all the way out when the striker assembly is moved slightly towards the rear, everything is okay. The more I think about it,this should be okay. When the slide is racked, the striker assembly would move towards the rear putting tension on the striker assembly spring and engage the sear. When the assembly started to move to the rear, the striker block would fully extend. At this point, if the gun was dropped and the striker assembly disengaged from the sear, the striker block would do its job and prevent the striker assembly from going forward all the way and hit the primer.

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M&P 40c; 40 FS; 40 Sh; 15 TS

I don't think this is right. Neither of my M&Ps do that. Both block the striker without me having to move it back at all.

This makes sense to a point. If the gun is working properly, the sear will move the striker back that little bit necessary to engage the striker block.

The scenario where the striker is not captured by the sear, thus allowing a drop danger, is very unlikely. Even so, I would still talk to S&W about it. I don't think it's right.

I am glad the gunsmith looked at it right away though.

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Freedom isn't free.

I think it is how I field strip Rastoff. I do the dry fire method.

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Ah, well that would seem to explain it, but it doesn't. If I do the "dry fire" method, my striker is still captured by the striker block. The striker return spring pushes it past the block every time regardless of how I take the slide off.

It is my contention that all of them should do this. Of course S&W is the authority and if they say it's OK, then I'll defer to them.

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Freedom isn't free.

Went to the range today to check out the new Apex FSS and trigger. All I can say is WOW.

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M&P 40c; 40 FS; 40 Sh; 15 TS

The Apex supplied spring is lighter than the S&W spring.

The answer may be to remove the striker block and make it fit the hole better. I can think of two ways to do that: either put the blocker on a skinny wood dowel and turn it lightly against some 1500 grit sandpaper, or take a tube of rolled 1500 grit sandpaper and insert it in the hole and turn it lightly (then remove the striker and flush chamber of any resulting grit or metal).

I had one in a Shield that did not function, essentially binding in the hole. I took it out, lightly sanded the outside of the block, and reinserted it -- and it moved smoothly.

So the spring might be factor, but there could be burrs on the blocker or in the hole, or even some grit in the hole. Or perhaps the block and the hole are not dimensioned exactly right - although they are probably pretty close. The small difference can be fixed with minimal intrusive work.

Two disclaimers:

1. I am not a gunsmith, and whereas I might do this procedure because I tend to just do stuff, usually with good results but sometimes not so much, I cannot give you a guarantee it will work.

2. I am pretty sure, though, you should never let a dremel tool near a gun. They are a lot of fun, but I would resist the temptation to use a dremel bit to open up the hole a bit -- it might over do it, as often happens with these home gun destroyers.

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S&W Rover

Rover:

Dremels are for mixing paint....

However, one of the "buffing devices" that came with mine is exactly the right size to polish a 9mm chamber ....

Don't ask....

My gunsmithing skills really run along with getting the grips back on the right sides of a 1911, so YMMV....

Regards,

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Stu.

My bad. Your right rastoff I edited my post to remove the misinformation.

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This is my first post as a new member. I have been reading and enjoying this forum for about a year. I have always appreciated the respectful and friendly demeanor of the members on this forum. The high level of knowledge and experience shared here is always interesting and useful to this S&W fan.

This thread has given me the opportunity to join and finally post something that may be useful.

I experienced the exact same striker block behavior as MP40cMN on my own M&P 9 Pro 5". I contacted Smith & Wesson and received a shipping label and RO number. I shipped my new pistol (unfired by me) back with a detailed description of the behavior. In addition to the detailed description, I also suggested a situation where the unblocked striker may cause an unintended discharge:

With a live round chambered, assume that pulling the trigger results in the striker striking the round, but the round does not fire. Without racking the slide, there is now a potentially live round chambered in front of an unblocked striker. In this condition if the pistol were subjected to a sudden extreme impact, the striker could possibly strike the round again and cause it to fire. I imagine this would require a really extreme event like being dropped from a great height or slammed with great force.

I realize that the chances of this combination of circumstances occurring would be near astronomical. If however, the striker block did not exhibit this behavior, the striker could only be unblocked on a chambered round with a pull of the trigger. I believe this to be the intent of the pistol’s design.

I may be missing something in the functioning of the pistol or the physics involved, but it was interesting to think about.

I received the pistol back from Smith & Wesson with a note saying “range tested/ meets spec”. No repairs were indicated.

My unfired pistol has now had the Apex DCAK kit installed. The trigger is now very much improved, but the striker block still behaves the same as before the kit installation. I plan to shoot pistol to verify its proper functioning and accuracy before considering any fix to the striker block.

The striker return spring should push it past the block every time. However, I don't think it does on some guns. I see this as a defect. Whether it's the spring or the block I can't tell without seeing a gun that does this in person.

Under normal circumstances you'd be right, but it is possible to have a chambered round with the gun not cocked. It's a ridiculous series of events, but it can be done; here's how:

• Remove the magazine
• Lock the slide back
• Lower the sear disconnect lever
• Drop a live round in the chamber
• Release the slide

There is now a live round chambered and the gun is not cocked.

I don't know why anyone would do that, but it is a way to have a chambered round and the gun not cocked.

Based on what we've discussed before in this thread, if the trigger is pulled it will allow the striker to go past the striker block. If the striker return spring does not push it back so the striker block can engage it, the gun could fire if dropped on the muzzle in this condition.

Again, the series of events to set this up are extremely unlikely and I don't know why anyone would do this. Still, it does present a possible hazard no matter how unlikely. Of course this is impossible in my guns because the striker block is always engaged no matter how the gun is manipulated. This is why I think it's a defect if the striker block doesn't engage the striker all the time.

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Freedom isn't free.

Tonight I cleaned my three M&P .40's after a range outing this afternoon. This thread explained how my striker assembly didn't seem to be blocked by the striker block after dry firing. The pistol would shoot fine but if you locked the slide back after dry firing, the striker assembly could be moved all the way forward.

As I was doing a thorough cleaning, I pulled the striker assembly. I pushed the spring down and rotated the white plastic sleeve. I got it out of alignment when i released the spring. I then re-compressed the spring and rotated the plastic sleeve into the correct position. I re-assembled the pistol after completing the cleaning and checked how the striker assembly was functioning. Try as I might, I can't get it to fail. It is always locked by the SB now. I am guessing that plastic sleeve wasn't positioned quite right in the past. I had taken it out before but never played with the spring and sleeve. Now everything seems fine. I will keep an eye on it but hopefully the situation has been rectified and won't happen again.

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M&P 40c; 40 FS; 40 Sh; 15 TS

This... it is a very common problem with the M&P line due to the machining process. Check the striker block channel for a burr and remove it, it is probably their due to the procedure they use to drill the channels. Grind it out and polish it with very fine wet sandpaper, followed with a polish with some compound. You should have seen the burr in my 40c when I put the APEX kit in it. The factory block was scored on the side.