It's been some years since SW and Walther entered into their Strategic Alliance, but as I recall reading and being told (during my first SW99/P99 armorer class), Walther (or the other company, Umarex) had originally wanted to make a licensed version of a revolver air pistol, for European sales, which was owned by S&W.
Part of their agreement & business alliance let S&W make a licensed copy of the P99 series, which gave them a newer plastic pistol to sell above their Sigma budget line, and which S&W called the SW99. S&W reserved the right to also make the QA (SW99QA) and DAO (SW990), although I never saw any, myself. Mentioned in the safety manuals, though.
They did make a weird version of the SW99 for the NJSP at one point, which was the standard configuration sear action (Anti-Stress), but
without a decocking button on the slide, at the demand of the agency (and against the recommendation of the company, we were told). That's a story for another day, but suffice to say were told that the reports of the gun being dropped due to functioning issues wasn't confirmed when S&W sent the guns to HP White Labs for independent testing (and purchased a LOT of duty ammo for the testing).
My second SW99 armorer manual actually included the SW99NJ (due to its different disassembly, and lacking the decocking button), and perhaps for that reason it may have some collector value someday.
S&W eventually requested a model variation of the QA sear action, which was numbered as the SW990L. When it was first being discussed (in my 3rd SW99 armorer class?), we were told the informal designation of the new version might be called the SW990Lightning (Quick Action trigger), but I never heard it referred to as that once the guns were being shipped. Just the SW99L, with the appropriate caliber/model identifier (SW990L40, SW990L45, etc). Oddly enough, for reasons known only to them, they decided not to incorporate the field-stripping button like the Walther QA had in its slide.
One interesting bit of trivia were given in one class was that after the lengthy discussions involved before S&W could convince Walther to design the larger framed .45 ACP model, they also apparently designed a revision for the new frame to permit the optional inclusion of a magazine safety (if requested by any agencies). We were told there weren't any examples of such a gun available, and that Walther would only make the frames (molded differently to accept the additional mag safety feature) if an order was placed for them. I never heard of any being ordered, to my knowledge (limited).
The SW99's incorporated some interesting changes from the Walther frames. I'll probably forget some of them this many years later, but I think those changes included a different accessory rail; different frame tang (flat, instead of pointed/hooked like the Walther version); different frame texture; different relief position for the thumb, front grip frame clearance to make it easier to grasp the mag foot to withdraw a stuck mag; and the use of the optional heavier extractor spring (which was also used for the mag catch, and which became standard in later S&W models); longer & heavier slide stop lever spring.
S&W made the bare slides and barrels for their licensed models, with Walther supplying all the other parts for the slide and the frames.
Another interesting bit of trivia we were given at one point was that S&W engineers also eventually helped identify the cause of the "early-slide stop" problems that affected early production P99 .40's and the SW9940's. They used their high-speed imaging to identify how the top rounds were being displaced leftward under recoil, bumping the slide stop lever's inner tab up into the slide during cycling, which could lock back the slide with rounds remaining in the mag. Walther had MecGar redesign the .40 mag body & followers to prevent this sort of wiggle.
S&W made some continual revisions and refinements to their slides and barrels. I saw ongoing changes to the feedramps, the chamber mouths, the muzzles and the bottom side of the barrel. This last revision apparently occurred in stages, as I saw different lengths of the new machined flat in later production barrels. The purpose, (we were told) was to create some clearance between the bottom of the barrel, at the rear, and the top of the recoil spring, when the gun was cycling. More clearance, less contact between the slide and the top of the spring coils. Ever hear a funny 'scrunchy" sound as you slowly hand cycle (an empty pistol & mag) some of the different makes of plastic pistols? That's usually caused by the top edges of the spring's rear coils rubbing against the bottom of the barrel before the barrel has been cammed back up into battery. (Also making it a good idea to rub some of that drop of oil applied to the barrel's exterior, down and around the bottom of the barrel.)
Walther wasn't sitting still, either, as they made some ongoing revisions and changes to their own models. They adopted the frame tang profile (which no longer had the pointed/hook that could press down into the web of the shooter's hand); the trigger guard profile changed; they changed their slide profile; the accessory rail (making it the more common type, to better accept a wider variety of accessories); polished their extractor hooks; dressed the locking blocks; introduced an ambi slide stop assembly; lengthened the mag catch levers; made a trigger change; and made some other design changes inside the frame.
I only discovered one of these last changes when I tried to replace an older sear housing block (broken ejector, which is molded into the caliber-specific housing block), and I discovered the dimensions of the new housing block was different, and the new sleeve pin wouldn't fit inside the older style frame. After discussing it with the factory, I had to substitute the sleeve pin from the older housing block into the new block.
You can see some of the differences between these spare sear blocks (viewed from bottom).
Walther typically doesn't want even armorers disassembling the sear housing block (and for
good reason). They do, however, provide armorers with instructions to reinstall the smaller plastic pin that holds the sear lever & its spring in the block ... because
that pin can fall out, releasing a sear lever & spring if the block is removed from the gun during an armorer inspection and tipped on its left side. Or, when a repair block is shipped in a plastic envelope. (Ask me how I learned
that the hard way when ordering some new blocks.
)
Another change in more recent years was the trigger bar guide post (located on the right/front lower corner of the housing block) being changed to an adjustable lever (on the right side of the housing block). The 2 trigger bar guide designs, and the sear housing blocks in which they're used, are NOT interchangeable between frame styles (and should NEVER be tampered with by someone not trained to work on the 99 guns, anyway).
Walther introduced some newer & tighter fitting rear sights in the subsequent 99's, too (including the PPQ variation). It uses a steel clamping sleeve in a steel sight base, instead of the plunger/spring used to hold the plastic sight in the dovetail.
When the Walther/S&W importation part of their strategic alliance expired last year, Walther decided to become their own importer and set up a US office on the East Coast. S&W still makes the PPk for them for US sales, and last I heard, Walther makes the frame (and some or all of the frame components?) for the M&P 22. I haven't kept up on any of the recent changes, though. Walther has (had?) another licensing agreement with another international business partner & firearms company to make yet another licensed 99 for US sales, BTW.
Now, looking at what S&W engineers seemed to have learned from the Sigma line (it's been many years since I took a Sigma armorer class, so I'm pretty far out-of-date on them), and then their association with Walther and the SW99/990L series guns, I can see where their eventual decision to make their own new polymer pistol probably benefited from all that experience.
This is a subject that could be discussed for hours, and just about every time I called to ask someone in the various S&W depts (repair, customer service, armorer training, etc) or their Walther America company, I learned something new and interesting. I also heard some often contradictory info, too, so it sometimes took repeated attempts to get something clarified.
Bottom line? The SW99 series guns are pretty decent, and are very under valued.
Now that Walther is going to be importing its own guns, maybe they'll start shipping more of them to the US, and increase their service and parts support. It would be nice if they eventually decided to extend the same sort of limited lifetime warranty, like they have for their American buyers of the PPQ, to the rest of their model line. A 1-year warranty isn't exactly competitive in today's American firearms market, in my humble opinion, anyway.
I know I sometimes had to wait for the "next" delivery of parts to be shipped from Carl Walther Germany, which apparently shipped at their convenience.
I thought it was pretty decent of S&W to offer their limited lifetime warranty to their licensed SW99's, even to covering the Walther components. Dunno what they're doing now, or that it's going to mean now that they've closed down the Walther America company and dispersed the guys from the SW99/990L production to elsewhere in the plant.
I know they still offer an armorer class for the SW99, and that at least a small number of LE/Gov users are still using them (even though S&W has probably offered to upgrade any existing 99 agencies to the M&P).
Okay, enough rambling off the top of my head.
