I bought a lightly used S&W 640-3 about four years ago. A friend’s elderly neighbor was thinning his collection and didn’t want his guns getting into the wrong hands. It was priced fairly, and I rationalized the purchase as an altruistic deed to help the man out.
The 640 was S&W’s first J frame .357 Magnum. It’s a dependable, no frills compact revolver. The frame, barrel, and cylinder are constructed of stainless steel, the thumb piece, trigger, hammer, and some internal parts are MIM components. This one was made in 2006 and came with the very unpopular internal lock as standard equipment.
The barrel measures 2.125”, compared to the standard 1.875” J frame barrel. That allows a longer extractor rod that ejects spent casings more reliably than ones with shorter throw. The 640 has slightly better sights than most J frames—it has a pinned-in front sight (at least it’s black and serrated) to go with the milled trench rear. The rubber factory stocks completely enclose the backstrap and extend past the bottom of the frame about 1/2”.
I wasn’t expecting much from it as a shooter. The trigger pull wasn’t great, and the sights didn’t mesh well with aging eyes for pinpoint shooting. It shot decently at 10 yards despite these handicaps. The 640 seems heavy for a J frame, until you start shooting .357 Magnums. I fired 20 mid-range .357’s through it, that was enough. Shot to shot recovery was slow, and my shooting hand developed a temporary tremble that turned into a few days’ worth of stiffness. The hard rubber stocks weren’t as forgiving as they looked. It’s nice to know you can, but shooting full house magnums in a J frame (even a solid steel one) is an activity to avoid. The 640’s weight makes it a “shoot all day” gun with .38 Specials, even +P’s. A middle ground between the .38 +P and the .357 Magnum would be the sweet spot in a gun this size and weight.
Shooting a bunch of rounds through a S&W 547 and an RIA AL 9.0 convinced me of the efficiency of the 9mm cartridge in 3” barreled revolvers. While testing the AL 9.0, I ended up on TK Custom’s website to order moon clips for it. They sell lots of cool revolver stuff and offer gunsmithing services– including rechambering certain .38/.357 revolvers to 9mm or .38 Super. TK’s rechambering includes milling the cylinder for moon clip use and chamfering the charge holes (a mod that any revolver benefits from). The more I thought about it, the more converting the 640 made sense. Eli from TK was good to answer my questions and offered his input on the conversion. A few side jobs later, the 640 cylinder was headed to Illinois.
In addition to the ballistic edge the 9mm cartridge would likely provide, ammo availability was a big factor. For months, it was nearly impossible to find factory .38/.357 ammo because of the COVID scare and related “supply chain” issues. Even today, internet searches reveal ample 9mm choices, but slim pickings in .38, slimmer still in 357. Moon-clipped empties also give an extraction advantage over loose cases; They cannot lodge underneath the extractor star. The short cases exit the cylinder as a unit and give the best chance of drama free ejection if a reload is required.
Shoot for the moon
In short order, TK had the converted cylinder back and I was spending range time with a large assortment of standard pressure 9mm ammo. I had worried that .355” diameter 9mm bullets wouldn’t shoot well in the slightly larger bore of the .357, my fears were unfounded. In most cases, the 9mm rounds shot on par with .38’s or .357 Magnums. One issue noted was 147 grain 9mm bullets didn’t seem to be stabilizing well and would occasionally hit paper off kilter. This wasn’t usually an issue with 135 grain and lighter 9mm bullets, and the 640 stabilized heavier .357”-.358” bullets fine.
The closest I could come to an “apples to apples” ballistic comparison was Remington’s first-generation Golden Saber. The .357 Magnum 125 gr. GSHP averaged 1,151 fps, while the .38 +P 125 gr. version ran 859 fps. The 9mm 124 gr. Golden Saber measured 1,010 fps: it was pleasant to fire, ejected easily and shot to the sights. Accuracy was good despite velocities being a bit inconsistent. The 124 9mm load hit that “sweet spot” I was hoping for in the 640.
To date, I’ve tried twenty-seven different 9mm loads in the 640. Of those, one FMJ load and one JHP load wouldn’t chamber. Both would chamber in the AL 9.0, the 547, and ran fine in semi autos. SAAMI spec on the widest part of a 9mm case shoulder is .391”. Most cases measured around .385” at the widest point and chambered easily. The cases that wouldn’t chamber fully were very close to maximum chamber diameter: the FMJ at .389”, the JHP at .388”. TK’s chamber is cut very tight– my suspicion is that it must be to maintain proper function with .38/.357 rounds.
TK Custom is very clear that no +P, +P+, or 9mm NATO ammo should be used. The SAAMI spec for the 9mm cartridge is 35,000 PSI, same as the .357 Magnum. Higher pressure 9mm ammo can result in cases sticking in charge holes and failing to eject. I experienced that with a few rounds that swelled in the chambers enough to cause difficult ejection.
One round from Double Tap demonstrated why TK frowns on +P ammo. It was loaded with Hornady’s 115 gr. XTP bullet and rated at 1,170 fps from a 4.5” barrel. The first shot registered 1,175 fps on the chronograph on a cold day. The trigger wouldn’t budge for a second shot. It took significant effort to push the cylinder out, the extractor rod had to be tapped with the demooner tool to eject the rounds. The brass and primer looked normal, so (genius that I am) I tried again. Round #2 produced 1,155 fps and again completely locked up the gun. The ammo wasn’t designated as +P, but it must’ve been. The case pushed rearward upon firing and struck the recoil shield as the brass swelled and pinned the case back. This kept the cylinder from rotating, and after getting it open, prevented the brass from ejecting. Double Tap builds great ammo, this load was just too hot for this revolver.
no jumping allowed
Bullet jump wasn’t an issue with this gun. Its weight and the lack of recoil produced by standard pressure ammo minimized it. I would check periodically by firing four rounds and then inspecting the remaining round. There was some movement with practice rounds (especially 147 FMJ) but not enough to cause problems. There was no discernable creep with modern defensive ammunition loaded with 115 and 124 grain bullets.
Blazer Brass 115 gr. FMJ would pull out of the case about 2mm by the fourth round. Its minimal crimp just doesn’t work well in revolvers. It was the only bullet of that weight that didn’t agree with the 640 and would sometimes keyhole at 10 yards– save it for semiautos.
The 9mm at standard pressure outclassed factory .38 Special +P loads by a significant margin with lighter weight bullets. Of all the loads tested, old Winchester 115 grain Silvertips (late 80’s vintage) impressed the most. They averaged 1,110-1,120 fps with low extreme spreads regardless of the temperature (30-90 degrees). The Silvertip chambered and ejected easily and grouped well, hitting to the sights.
Atlanta Arms’ 115 gr. JHP was noteworthy for its high, consistent velocities and accuracy as well. Remington’s 124 gr. Golden Saber and Speer’s 124 gr. GDHP weren’t quite as consistent but would work for those preferring a more modern bullet. If I end up in the boonies with this gun, it shoots my “woods” handload well. A .357 180-grain cast WFN that runs 1,042 fps from a 4” Model 66 averages 910 fps from the 640. Heavy bullets with wide fronts don’t need to be supersonic to achieve needed penetration.
get a grip
Shooting .357 Magnums pre-conversion had convinced me that the 640 needed different stocks. Massad Ayoob recently wrote about equipping a S&W M&P 340 with Crimson Trace LG350-G laser grips to help with the light weight’s recoil. The LG350 offered more width and cushion behind the gun’s frame than the LG405 “boot grip” that I was familiar with, and the green laser was allegedly visible in more lighting conditions than red.
I cashed in some hoarded Cabela’s gift cards and ordered some. They’re a little shorter than the factory stocks and don’t add any weight (the 640 weighs 23.2 ounces w/ factory stocks, 22.9 ounces with the LG350’s). The pressure pad is nestled in the top finger groove and is less pronounced than on the LG405. It’s harder to engage, but a conscious squeeze of the middle finger will activate them. The green laser worked as advertised, visible on an overcast day. The LG350 fits my hand well and assists wonderfully (Ayoob was right) in recoil mediation.
The CT Laser Grips were a good add but couldn’t make up for the 640’s sights in all conditions. The sights slowed me down when shooting rapid fire drills- the shallow rear notch and short front sight were a vexing combination. I had tested D&L Sports’ excellent fixed revolver sights on an N frame recently and was sold on their functionality. Dave Lauck started making them because he got tired of waiting for S&W to put decent sights on J frames. The 640 had proven itself worthy, so off to Arizona it went. Dave machined the frame for his rear sight and mounted a tall square front post with a red fiber optic tube. He zeroed the gun and had it back to me swiftly.
These sights come close to perfect for this gun’s mission. They’re tough fixed sights befitting of a carry gun that provide a great sight picture. All J frames should have sights like these! The factory sights were likely factory regulated with 158 grain bullets, but 115 and 124 grain 9mm bullets gratuitously impacted to point of aim at 3-15 yards. 135’s and 147’s struck a little high. This trend continued with the new sights, but it was much easier to put hits on target with them. On a side note, the 640’s yoke screw was a bit boogered when it journeyed to Lauck. When the gun returned, the screwhead had been cleaned up and looked brand new. That’s the kind of guy that Dave Lauck is.
The 640 was a little too big for pocket carry and too heavy for an ankle holster. It was going to be a waistband gun and the holster was an easy decision. I’d been using a Phlster City Special AIWB rig for a Ruger LCR with complete satisfaction. The sight track looked like it would clear the tall front sight Dave had installed. An email to Phlster confirmed that and the order was placed. Upon its arrival, I installed the longer “cleat” onto the mod-wing to better push the grip against my body. It worked like a charm- even with the larger grips the gun hides well and rides comfortably and securely.
TK Custom sells a moon clip holder designed for concealed carry that looked like it would protect the clip and still be accessible. I ordered one and was pleased to see the name “Del Fatti” on the packaging when it arrived. It carries well in a jacket pocket, holds the clip securely and prevents bending or damage. Adding the moonclip to my EDC load out of a 2X2X2 pouch and a 4 round speed strip made carrying 15 extra rounds painless.
unlocking its potential
The only thing that wasn’t right about the 640 was the internal lock. Eli came to my rescue and sent one of TK Custom’s replacement plug kits. The kit consists of a plug and a retainer; After watching the short YouTube video, installation was easy and took about 10 minutes. The plug fits like a factory part and provides peace of mind against the lock breaking or malfunctioning. I messed up and ordered the matte finish instead of the polished, so it doesn’t quite match– but I like the way it looks. It draws attention to the gun’s “lack of lock”.
The rechamber has added to the ballistic efficiency and versatility of this little gun. It required some trial and error to guarantee function and maximize performance, but it was time well spent– a bullet nerd’s vision quest!
The few issues experienced taught me to buy ammo in small quantities until it was proven. With ammo it likes, moon-clipped empties fall out of the gun when inverted. The charge hole chamfer makes a big difference in the speed and ease of loading .38’s/.357’s back into the gun.
It’s been dry fired and shot so much that the factory trigger is now acceptably smooth. I couldn’t be more pleased with the sights on this gun, and the laser grips finish it. TK Custom and D&L Sports upgraded this revolver from Plain Jane to “Custom 640/940 Pro Series” and the pride of ownership is difficult to quantify. It’s gone from “most likely to be traded” to “most carried” status. Not sure I can give it any higher praise than that.