A Pretty Capable J-Frame

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.

magnum force

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 author bought this 640 in 2019 to help a guy out.

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”.

The 640’s extractor rod (Left) is longer and has a greatly superior throw to the 442’s (Right).

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 +Ps. A middle ground between the .38 +P and the .357 Magnum would be the sweet spot in a gun this size and weight.

Metric system

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.

The 640’s cylinder, after coming home from TK Custom. Note the moon clip cut and charge hole chamfering.

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.

The extractor rod, at full extension, easily clears moon-clipped 9mm casings.

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 640 stabilized most 9mm bullet weights fine—the exception being the 147s, as demonstrated by the Federal American Eagle FMJs, pictured here. The target was shot at 10 yards.

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.

Remington’s original Golden Saber gave a good basis for comparison between the three calibers.

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.

A few rounds (like the Sig V-Crown, pictured) were too close to max shoulder diameter to fully chamber.


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.

Some practice ammo experienced visible bullet jump, but not enough to effect function. Federal American Eagle 147 gr. FMJ-FP pictured.
Premium defensive ammunition, like Speer’s 124 gr. GDHP, showed no noticeable bullet jump.

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.

Speer’s Blazer Brass 115 gr. FMJ exhibited noticeable bullet jump and wouldn’t stabilize. Note the shotgun-like pattern at 10 yards, complete with a few keyholing bullets.

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.

The oft-maligned, Winchester 115 gr. Silvertip was a stellar performer in the 640.
Old 115 gr. Silvertips hit to point of aim with the factory 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.

Remington’s first generation, 124 gr. Golden Saber shot well and hit to the sights, despite inconsistent velocities.
Heavy-for-caliber, .357 Magnum cast bullet loads like the Corbon 200 gr., the Federal 180 gr., and the author’s 180 gr. handload, make the little 640 “woods ready.”

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.

Crimson Trace LG350-G Laser Grips were a worthy addition to the 640. They provide exceptional recoil control with hard kicking loads.

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 proveitself 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.

Adding D&L Sports J frame sights to the 640 took it to a new level.
D&L Sports J frame rear sight. It is without equal.
Lauck installed this tall, serrated post with a red, fiber optic tube.

These sights come close to perfect for this gun’s mission. Theyre 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 first five rounds of old Silvertip fired with the 640’s new sights: Off hand at five yards.
Lauck zeroed the gun with Speer .38+P SB 135 gr. GDHP. These are the first five rounds of that ammo fired from the 640 at 10 yards.

Packing it

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.

The Phlster City Special was the right holster for the 640. It fits the barrel length and sight height, and provides superior comfort and concealment.

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.

The excellent concealable moon clip carrier sold by TK Custom was made by Del Fatti Leather.

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 matchbut I like the way it looks. It draws attention to the gun’s “lack of lock”.

TK Custom’s replacement plug for the internal lock is well made and provides peace of mind.

Success story

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 custom 640 is now the author’s most carried gun.

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.

TK Customs’ 9mm conversion greatly added to the versatility of the 640. There are lots of ways to feed it.

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.  

Author: Kevin McPherson

Kevin McPherson began his career as a police officer in New Mexico in 1987. He served for 23 ½ years, the last 19 ½ with the New Mexico State Police. There he worked in the uniform bureau and narcotics enforcement section and did two tours in the NMSP Training Bureau, retiring as a Sergeant in 2011. Kevin ran the firearms program and was the chief armorer for NMSP for 13 years. He served as a member of the NMSP Tactical Team (SWAT) for 10 years, eventually becoming the counter sniper team leader. He was commander of the NMSP Pistol Team and competed with a revolver throughout his career. He is a master firearms instructor through NMDPS and continues to instruct in retirement. He has had several articles published in American Cop Magazine, SWAT Magazine, and the NRA Law Enforcement Quarterly. He started his career carrying a revolver and has always been partial to them.

21 thoughts on “A Pretty Capable J-Frame”

  1. As much as I enjoy my semi autos, the only handgun I carry is a Smith J frame 640. While it’s not tricked out nicely like the author’s, it’s totally reliable, or as reliable as a handgun can be. My semi autos–not so.

    1. Spencer,
      Your comment struck me as particularly powerful. “it’s totally reliable, or as reliable as a handgun can be.” Well spoken, Sir.

  2. That’s fascinating, thank you for the write up! I have (or had- we’ll see when the dust settles) a similar beast from the late ‘90s with a three inch barrel and target sights, which I’d love to custom up like that… I have to ask, could one use moon clips with .38 or .357 in this weapon as well? Thanks again for taking the time to write about this.

    1. You’re welcome, Riley! I enjoyed every minute of it. Yes, when TK Custom finishes the conversion, that’s one of the benefits- it will work with moon clips for .38/.357 also. I apologize for not making that clear.

  3. Thanks for sharing this excellent side project with us but I gotta ask; how much did all of the extra work cost on top of the initial purchase? It’s great you’re happy with the end result but with the rechambering, upgraded sights, laser grip, lock delete, and moon clip holster it couldn’t have been cheap. A lot of money spent for only a five round capacity is certainly a passion project reserved only for the most hardcore revolver fans (which you clearly are).

    1. Thanks for writing, Jeb. There’s no doubt that the custom work was expensive, but I wouldn’t use the gun’s capacity as a yardstick to measure whether or not the expense was reasonable. If you decide that a 5-shot, small frame revolver is the best tool for your specific need, and you’re willing to spend some extra money to optimize it for the job, I think that’s a good call. One could easily take the opposite approach and argue that “only” having five shots is a great reason to make sure the gun is worked over, to ensure you can get the most out of each one.

      I think this custom snub would be hard to beat for the mission Kevin uses it for. I know he has other guns, with greater capacities, that he can carry when it’s appropriate. But if you need a snub . . .

    2. Hey Jeb, you’re welcome. You are correct, it wasn’t cheap and a “passion project for a hardcore revolver fan” is accurate. I am that, and I’m well pleased with the end result of the investment. You could buy a quality semi auto nicely equipped with triple the capacity for what I now have in this 640! When I committed to the rechambering, I decided to go all in. Mike does a good job describing my thought process in that, if it only holds five, I want it to be the best it can be. I like to carry small revolvers that hold six, but the end result of this project made me comfortable with five. It’s pretty capable for what it is. Any of the upgrades I have done will make your J frame better, you don’t have to jump off the cliff like I did! 🙂

  4. Kevin thank you for the excellent article on getting a new carry gun and making it your own, sights, grips, holsters, best loads and accessories like speedloaders..

    The same road we all need to walk down when we have selected a new firearm to serve as protection for self and others.

    One of these days maybe we will get to punch holes in paper. I know I would benefit from your knowledge and experience.

    1. My pleasure, Tony. Thanks for reading it! It was educational and I now have a great deal of pride of ownership in this little revolver. I can recommend TK Custom and D&L Sports wholeheartedly; they put magic in this J frame! I hope we get to do that someday, my friend. I would also benefit from your knowledge and experience. Obliged!

  5. I sent my 640 off to Eli last year for his “basic” trigger job and I think the name is very deceptive. Not only did it come back with an 8.5lb DA trigger that cracks all primers, Eli also chamfered the charge holes. It took my 640 from a gun I shot reluctantly to one I’m excited to take to the range.

    1. Hey Jeremy, Eli has a way with 640’s! Amazing how guys like him can convert reluctance to excitement, huh? I applaud your choices; I’m sold on chamfering charge holes- good medicine…

      1. I like what you did with the sights too! I didn’t go that route but I opted for an XS dot (the standard size, not the big one) and it’s a big improvement over the factory serrated ramp. That might be a more accessible option for folks who are not yet ready to send their gun off to get milled.

        1. Thank you! I think that my eyes are getting too old for iron sights until I shoot a revolver in the sunlight with Dave Lauck’s sights. His give me hope! As you point out, XS sights are beneficial, too. Every little bit helps on a J frame!

    1. Thank you, Anner! It kind of flows easier when you have good content to write about. I’m proud to brag on the work that TK Custom and D&L Sports do.

  6. Kevin, that is one sweet gun for sure !! My problem would be that I wouldn’t want to carry it – but that’s my hangup. One can only wonder whether we’ll ever see something from the S&W Performance Center like your 640 . . . .38, .357, 9m/m, all in one gun. Sort of the ultimate multi caliber revolver. ( hint, hint, nudge, nudge, a wink is as good as a nod, S&W )

    1. Thank you, Sir! This one was built to carry, and I do so often! That would be pretty neat to see a factory version. If they want to start with a scandium framed 3-inch K frame in .38 Special/.38 Super, that would be okay, too…

  7. I carried a pre-lock 640 in the late 90’s early 2000’s and was quite happy with it. One thing I did note was the cylinder would start to bind on the cylinder pin after shooting an unremembered number of magnum rounds through it. It never locked up but the trigger pull became very heavy. Apparently combustion gases found their way in between the pin and the cylinder. So after a practice session I would always pull the yoke and cylinder off and clean them. Something to think about with all revolvers.

    1. Hey Brett, You bring up a good point on a critical maintenance area on d/a revolvers, especially with high round counts and/or hot magnum ammo. The Yoke barrel (S&W parlance) needs to be clean and fouling free to insure smooth function. That may be an area we should cover in the future…

  8. A revolver in 9mm Luger doesn’t appeal to me, personally…but I can definitely see the appeal in it from an ammunition availability + pricing perspective.

    It’s almost criminal how much cheaper and more widely available 9mm is over .38 Special right now. The cheapest box of .38 FMJ I recently got was $23.95. I paid $13.95 for a box of 9mm FMJ, also from SGAmmo.

    And .357 Magnum? Fuggedaboudit

    1. Yes sir, 9mm is appealing right now if you actually want to shoot your snub guns with factory ammo. Locally, 9mm FMJ best price is 17.99 per 50 rd box. .38 Special is running 31.99 a box, and finding it is still iffy. I have been waiting for four years to find a box or two of Speer 135 gr .357 Short Barrel GDHP.
      If you handloaded ammo and had a good supply of primers when COVID hit, you are looking pretty wise in the aftermath.

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