I've previously posted some of my thoughts and impressions of the M&P pistols series.
I was surprised by how well I liked the design of the M&P when I attended an armorer's class. There are some surprises to the design.
There are several very interesting design features used in the M&P pistol.
The stock triggers are intended to produce a trigger pull of 6.5 lbs, with a +/- 2lb tolerance range. Yes, that's plus/minus of 2 lbs. That means you might occasionally get one on the heavier end or the lighter end. There's a heavier trigger available for those states (or contracts) which require it. The .45 has a little bit heavier trigger.
Disassembly is pretty simple, but then I didn't mind depressing the ejector plate of the Ruger P-series pistols for disassembly, either. Getting the tool out of the grip pin is a bit of a chore the first couple of time, but then I use an armorer's pin punch to move the sear deactivation lever, anyway (and leave the tool/pin in the grip unless I need to change the grip insert).
The locking block pin should stick out just a bit on the left side of the frame. The left end of it should be level with the outside (taller) portion of the side of the frame to act as a "stop" for the take down lever. This is intentional, and protects that part of the frame from the takedown lever being over-rotated.
The incorporation of the front frame rails into the locking block reminds me of the Walther P99 Compact (which also puts the front frame rails in the locking block, instead of using an insert molded in the frame as in the standard size models). The incorporation of the rear frame rails in the steel sear housing assembly is also interesting. This design essentially means that if a frame rail were to ever break (hard to imagine with the large, robust rails), the broken rail could easily be replaced by simply replacing the locking block or the sear housing assembly. The repair can be done by an armorer, and the frame doesn't have to be returned to the factory.
The frame rails themselves are rather robust and interesting in design. S&W calls them 'rocker rails', and their shape not only permits 'centering' of the slide rails onto the frame rails, even as normal wear occurs, but we were told their shape also reduces stresses on the rails themselves.
I like that the sear housing is made of steel. I like how the ejector snaps in and out of the housing. I like the robust appearance of the ejector, too.
The magazine springs have a Teflon-based finish to help with smooth functioning. I like the steel magazine bodies.
The captive recoil spring assembly uses a stainless steel guide rod because S&W felt it would provide better strength and durability. This is something for which Glock owners have long expressed a desire.
The front of the slide's dustcover (which houses the front of the guide rod) was made thick and strong, to resist damage if a slide is dropped 'muzzle forward' onto a hard surface. (You have to watch cops standing around a cleaning table/station to really appreciate this feature.)
The 'I-beam" extractor surprised me with its design. The extractor is larger and stronger in appearance than any S&W extractor I've ever seen, especially the extractor hook itself. Robust is an understatement, I think. It's also interesting that S&W found a way to make the same extractor work across the range of various calibers, too.
The .45 models use a roll pin for the extractor pin instead of the solid pin used on the other calibers (and which is typical for S&W). We were told the roll pin was used to satisfy an expected military requirement (as were the addition of the thumb safety levers) if military pistol trials occurred.
I like the idea of the striker return spring used in the M&P striker assembly, too. I felt the same way about the similar design of the Walther P99 striker assembly design. I remember when I attended my first SW99/P99 armorer class and the purpose of the striker return spring was explained as being to help prevent unnecessary contact between the firing pin and the plunger. This sort of repeated contact may result in a peening condition which has been described as 'chatter', and normal, in Glock armorer classes.
There have been some minor changes, improvements and refinements since the early pistols were introduced.
The early flat engagement pads of the slide stop levers received a different shape after feedback from folks who prefer to use the levers as 'slide release levers'.
The tension of the slide stop lever spring was increased.
The hardening of the metal insert in the magazine catch was changed. Some earlier magazine catches had metal inserts which were too soft and which resulted in some magazines being unintentionally released.
The 'foot' of the striker was changed, with more material added to the front of it, so the striker is retracted a bit more before being released (there are some hard primers out there in some ammunition).
The yellow sear deactivation lever shape was changed after the early guns were released, essentially for ease of reassembly if a user was a bit 'inattentive' regarding its position when installing the slide onto the frame after cleaning. The original one has a dog-leg curve and the current one is straight at the end.
I was told several months ago that S&W was in the process of redesigning their striker to make it more tolerant of a lot of dry-fire.
The design features are impressive. I was repeatedly struck by the elegant simplicity of some of them. The magazine safety is 1 lever and a spring. After examining how it functions I wouldn’t be bothered by having one in a personally owned/used M&P, and the M&P 40c I just ordered is coming equipped with one. Much simpler than the magazine disconnect safety in the traditional S&W pistols, and I’ve used those for many years without problem. The way the lever sticks out into the magazine well, however, means that a rag or shop towel should NOT be rammed through the grip frame in some sloppy, improper semblance of a cleaning method.
The ergonomics are very good. The feel of the 3 grip inserts are great. The 18 degree grip angle, combined with the low bore axis and extended frame 'beavertail' (to help prevent 'slide bite'), are an excellent combination. One of the other instructors who carries a Colt 1911 commented that the smallest of the inserts provides him with a grip that feels remarkably similar, and points similarly in his hands, to that of his 1911 equipped with a flat mainspring housing.
I like that the M&P pistol was originally designed and built around the .40 S&W cartridge, instead of being a beefed-up 9mm.
The Melonite QP used to treat the through-hardened stainless steel slides and barrels of the M&P pistols is a nitrocarburizing surface hardening treatment. The black color is a property of the Melonite hardening treatment.
Some basic info on Melonite:
"Through-hardened", referring to the slides and barrels themselves, basically means that instead of being just surface or case hardened, the stainless steel components have been hardened throughout. Then, the slides and barrels receive the Melonite nitrocarburizing treatment.
FWIW, the Melonite nitrocarburizing treatment the M&P receives results in a surface hardness of 68 HRc, which is a little harder than the 64 HRc of Glocks which receive the nitrocarburizing treatment marketed under the Tenifer trade name.
My M&P 45 Dark Earth w/thumb safeties has had more than 2,300 rounds fired through it to date. It's been consistently reliable with a mix of 3 different duty-type hollowpoint loads and has demonstrated itself to be very, very accurate. It's become my favorite personally-owned .45 pistol to use for training & practice.
I've only spoken to a handful of folks from other agencies where the M&P's have either been adopted or have been undergoing extended T&E for either eventual adoption as issued or optionally approved weapons. So far the folks with whom I've spoken have been pleased with them.
The M&P pistol series has a lot going for it, and it's done very well in LE circles considering it was only released in Jan '06.
I think it's become a nice option among the other high quality service pistols.
Just my thoughts.