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Thread: An afternoon with a 9mm J frame notes

  1. #1
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    An afternoon with a 9mm J frame notes

    Shot a 940 S&W yesterday. Interesting. Some general notes for curious 9mm revolver readers to follow:

    Shoots to point of aim with 147 grain bullets. Progressively lower point of impact as bullets got lighter. I saw 4 inches low at 10 yards with 115s.

    Works fine without the full moon clips. Punching out the empties of course awkward.
    The ability to at least function without a clip is important to me. My otherwise preferred L frame 9mm will not fire (reliably) without clips. The Ruger LCR9 shares the ability to function without clips also. I have forgotten to bring clips to a range session...

    Steel case ammo almost needs a large hammer to extract. NOT recommended.

    Felt recoil (for me and using 147s) was stout but do-able. Less than an Airweight .38 (unless using target WCs) but more than a Kimber K6 using 135 Short Barrel .357. All revolvers were fitted with Crimson Trace grips. CT grips being LG-305 for 940, LG-405 for Airweight, and CT LG-950 for the K6.

    Both pistols are nearly identical in size.

    The K6 is the better choice. Much better sights, slicker DA pull (this 940 being a better than average J frame sample), and 6 rounds vice 5; the tradeoff being 1 ounce more weight and the necessity to use snap caps to protect the firing pin during dry fire practice with the K6.
    My apologies to weasels.

  2. #2
    Member Zeke38's Avatar
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    Been entertaining the J frame size 9. Appreciate your observations. I have a couple of K6s, I'll stick with them. I did purchase a spare firing pin kit from Midwest gun a few months ago but haven't needed to use the kit or the pin. I do dryfire with snapcaps.

  3. #3
    Member GearFondler's Avatar
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    I'd like a K6 in 9mm but I'm weird like that.
    And I worry if the K6 would be too big for front pocket carry (for me)... The weight is not an issue. The length might be. I've never actually held one.

  4. #4
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    The overall length of the two revolvers is very close with the listed grips. However, when I compared the two while they were inside an A-Holster kydex pocket holster, the K6 was about an 1/8 to 1/4 inch shorter OAL. Something about the way it nestles into the holster. Of course the K6 is a very small amount wider as well.
    My apologies to weasels.

  5. #5
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    I've owned a 940 for years. It is a superb handgun. I acquired mine from a fellow officer who had purchased it for his wife; he carried a 9mm at work and wanted a revolver that he didn't have to buy different ammo for. They took it to the range a few times and she didn't like it. One of the problems I discovered was the crappy grips that had come on it threw the balance way off and the recoil was horrendous. The grips kept the shooter from getting a high enough grip on the backstrap for control. I offered to change out grips for them to try but HER mind was made up; so I gave him the cash he asked for and took it home. First thing those grips came off and a set of Rogers went on. Now that I could get a high grip on the backstrap shooting became a breeze (sorry Paul, but I tried to tell you...). The felt recoil when tested out against my 640 was actually less. Accuracy was consistently good with 124 gr HP's. With the full moon clips it became my backpacking/hiking gun literally disappearing in my pocket or a fanny pack (on day hikes).

    A few years ago I took it on a camping trip with friends. We were shooting at targets and the darn thing jammed. Yes, I said a revolver jammed. After several minutes of cussing and discussing we took it into my friends shop. Careful application of force to the cylinder finally yielded an open firearm. The problem was found to be a "high primer" on a 9mm reload had jammed the cylinder before it could get into battery. LESSON LEARNED: If you are using reloaded ammo examine the case heads before loading them into a revolver. Of course everyone should never carry reloads for serious social work; however, a couple of extra minutes when loading up your moon clips even with factory fresh stuff can save you headaches (and heart-aches) later.

    My 940 continues to serve; although my 638 has now taken it's place in the pocket holster; these days, lighter is better.

  6. #6
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    C.E. Harris article on the S&W 940

    Previously published by the Snub Gun Study Group and posted here by permission.

    A Tale From The Back Creek Diaries – C.E. Harris - A practical treasure, the S&W 940, a 9mm Parabellum/.38 S&W pocket revolver

    In the 1980s Ruger engineers rechambered leftover French Model Ruger Service Six 9mm revolvers to .38 S&W in order to jumpstart a police revolver order for India. The first few thousand India .380 Rimmed Models could use either 9mm Parabellum with clips, or .38 S&W without.

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    I’ve always felt that this dual-ammo revolver was a “cool” idea, but once the leftover French parts were used up, the balance of the India contract was filled by purpose-building .38 S&W chambered revolvers. [The Ruger "380 Rimmed" revolvers are the strongest ever produced in this caliber and thrive on a steady diet of full-charge 147-grain 9mm handloads assembled in .38 S&W brass which would take apart your WW2-era S&W Victory!] My fantasy of a dual-caliber DA wheelie faded until I was gifted an S&W 940 from the estate of a Naval Officer friend who recently passed. I knew that the “Ruger mod” could be done on an S&W and indeed work.

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    For those unfamiliar, the S&W 940 was a stainless Centennial J-frame, chambered in 9mm Parabellum which was produced with 1 7/8’’ barrel from 1991-98. A few were made during 1991-92 having 3’’ barrels. The advantage of using clipped ammunition in a revolver is its potential for fast reloading. The short ejector rod of S&W J-frames works better with short cases like the .38 S&W or 9mm than it does with the longer .38 Special. The Model 940 was never “popular” because reliable functioning required more care and attention than using a similar .38 Special revolver.

    Most 9mm +P and +P+LE ammunition causes hard extraction in revolvers because fired brass sticks in the chambers. If chambers are the least bit oily, the tapered 9mm case is prone to set-back against the recoil shield, causing hard cylinder rotation. This doesn’t happen with cylindrical .38 Specials which are loaded to lower chamber pressure. It takes practice to remove spent 9mm brass from the clips without bending them. A bent clip causes hard cylinder rotation, light primer strikes, and heavier trigger pull. Internet reviewers of 9mm revolvers usually recommend that only new clips be used for defense carry, and that used ones be reserved for training and practice only. Potential purchasers of used S&W 940s should inspect the gun carefully, because some users honed or polished chambers in attempts to ease hard extraction. Doing so actually makes the set-back problem worse, because fired cases then don’t adhere as well to the chamber walls and more easily “piston” back against the recoil shield. The following advice comes from the S&W user’s manual:

    “In the Model 940 revolver, some brands of 9mm Parabellum ammunition may cause difficulty in extracting spent cartridge cases from the cylinder. If this situation occurs, thoroughly clean the cylinder charge holes with solvent. If this condition persists, we recommend changing to another brand of 9mm Parabellum ammunition.”

    The chambers of the S&W 940 must be kept clean, DRY, and free of oil to avoid fired brass from “pistoning.” The S&W user manual, further states:

    “Whenever rimless pistol cartridges are used in the cylinder of a Smith & Wesson revolver, (except M547) full or half-moon clips MUST be used to both position and extract such cartridges. Failure to use ammunition clips with rimless cartridges may result in malfunction of the revolver.”

    My experience has been that in firing standard pressure (avoid +P) 9mm loads, if the chambers are clean and free of oil, fired brass falls right out. But, firing clipped +P ammo, it usually takes a mighty whack (or two) on the ejector rod! My revolver fires standard pressure 9mm ammo without the clips, but fired brass must be poked out with a BIC pen or similar object. I’ve had no problems in either of my two 940s firing non+P 9mm ammo, without using the “star clip,” as long as the “duty pen” was kept handy.

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    I modified the chambers of my two 940 revolvers to permit use of either 9mm Parabellum or .38 S&W ammo. This is accomplished by enlarging the ball seat entrance diameter to permit lead bullets of larger diameter to enter and transition smoothly into the .356” diameter chamber throats without experiencing “trailing edge failure” caused by base upset. I carry clipped 9mm 147-grain JHPs for defense, but use standard pressure 9mm FMJ without clips or .38 S&W reloads for practice and recreational shooting. My 9mm cast loads approximate the payload and velocity of common .38 S&W LRN or .38 Special wadcutter loads, using 3.2 grains of Bullseye with the Accurate 36-142H sized to .358.”

    Because people will ask, I will describe the .38 S&W lead-bullet cylinder modification. Be advised that doing so voids any factory warranty, so if you choose to do this, you are on “your own nickel.” S&W doesn’t have replacement cylinders for the 940 and I am told that they don’t service this model anymore, so consider yourself fore-warned. I hand-reamed the origin of the .356” diameter cylindrical ball seats to provide a gentle transition cone of .359” major diameter, using the Brownell’s .22-.32 revolver 11 degree revolver forcing cone reamer, and breaking the corner of the case mouth stop surface, so that it is less likely to drag a ring off the trailing edge of the bullet base. The reamer’s .375” shank diameter serves as a pilot to align the reamer in the 9mm chambers.

    Before reaming chambers are swabbed with Brownell’s Do-Drill. The reamer is then threaded onto its T-handle, and the stripped cylinder held vertically with the reamer resting against the chamber stop surface of its own weight, attached to the T-handle only. Using only very light finger pressure, I simply twirled the T-handle, stopping to inspect after each 20 turns. This produced some fine stainless steel “flour” mixed with cutting oil on the reamer flutes. After wiping the chambers I checked my progress by dropping five soft lead .358” diameter Magtech 158-grain LRN bullets into the chambers, pushing them into the ball seats by hand using a Brownells Compact LE screwdriver handle. I then tapped each bullet firmly into its ball seat with a 2-oz. brass hammer, then tapped them back out to visually inspect and measure them.

    Visual inspection showed that the lead slugs entered the ball seats smoothly without shaving. Where the bullet foreparts were pressed into the uncut portion of the cylinder throats, ahead of the short 11-degree cone, they measured .356” and the bullet shank at the ball seat entrance measured .3575” after the initial cut, being lightly sized by the modified chambers. So, I oiled the cylinder again and repeated the process, another 20 twirls around all 5 chambers. After finishing the reaming I used a Brownell’s 3/8” ball chamfer tool to break the wire edge left on the reamed ball seats of each case mouth stop surface, then I slugged the reamed chambers again. Ball seat entrances after the final cut were .359” with a short 11-degree taper to .356,” without any sharp corner apparent to visual inspection. Upset slugs entered the origin of the cylinder ball seats without deformation. Factory 9mm rounds still drop in and headspace properly without clips. Factory 146-grain lead RN .38 S&W rounds headspace on the case mouth and bullet ogive, their rims standing slightly “proud” to make up the difference between the .38 S&W rim and clipped 9mm Parabellum rounds.

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    I fired an assortment of factory 9mm loads and .38 S&W 146-grain LRN to see which ammo shot closest to the sights. Also important was to confirm that there was no tendency for lead bullets to leave lead rings in the chambers due to trailing edge failure, a common problem in 9mm revolvers. Test firing after the chamber mod confirmed that this issue had been successfully mitigated. Standard velocity 9mm 147-grain ammo exceeded the velocity of Special +P of similar bullet weight, fired from a similar snubby. Jacketed 147-grain 9mm and 146-grain LRN .38 S&W factory loads both shot to the sights. But 9mm ammunition with 115-grain bullets struck 4 inches low at 50 feet and 6 inches low at 25 yds.

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    Keep in mind that the stated barrel length of a semi-auto pistol includes the chamber, while the stated barrel length of a revolver does not. So the bore travel and expansion ratio of a 1-7/8” Ruger SP101, LCR or S&W 940 in 9mm is about the same as the 3.1″ barrel of a compact 9mm auto such as an S&W Shield. Paul Nowak, at Winchester, stated that the 147gr Winchester Ranger Talon (symbol RA9T) is designed to expand at low velocities produced by the smallest of semi-autos, not substantially greater than .38 Special target wadcutters fired from a revolver of similar barrel length. While unable to find that specific load, I fired several brands of 147 grain JHP ammunition into gallon water jugs from the 940, as well as .38 S&W lead factory loads and my 9mm lead-bullet hand loads. Results are summarized in the accompanying table:

    Table 1 - Velocity Data for S&W Model 940 Revolver with 1-7/8” barrel and 0.008” cylinder gap.

    R-P .38 S&W 146-grain LRN__________________671 fps, 26 Sd_Shoots to fixed sight POA
    CCI Blazer 9mm 115-grain FMJ_______________1062 fps, 26 Sd_Point of impact 6 inches low at 25 yds.
    Winchester 9mm 115-grain FMJ______________1091 fps, 31 Sd_Point of Impact 6 inches low at 25 yds.
    Federal 9mm A. Eagle 147 FMJ_______________924 fps, 7 Sd_ Shoots to fixed sight POA
    Winchester 9mm Ranger T-Series 147 JHP______920 fps, 14 Sd – good exp. stopped in 3rd [gallon]water jug
    Winchester 9mm White Box 147 JHP___________882 fps, 19 Sd – fair exp. Stopped in 4th water jug
    Federal 9mm HST 147 JHP___________________945 fps, 8 Sd – Impressive exp. Stopped in 3rd water jug
    Last edited by Outpost75; 06-09-2021 at 07:56 PM.

  7. #7
    Great write up. Thank you.

    I’m unfamiliar with the concept of trailing edge failure. If it’s not too much trouble, would you mind explaining to some of the slower students in the class?


    Sent from my iPhone using Tapatalk

  8. #8
    Member Rock185's Avatar
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    314159, Thanks for starting this interesting thread. I admit I like 9mm revolvers, and had a few over the years. Here's my 2¢ worth on the 940; even though the 9mm 940 weighs ~5 Oz. more than a .38 642, the perceived recoil of the 940 is greater to me than with any .38 +P I've used in the lighter 642. I can't offhand recall any factory .38+P 125 grain I tested in the 2" 642 that hit 850 FPS. In the 2" 940, standard pressure Federal 9BP 115 JHP averaged 1013 FPS, standard pressure 147 Gold Dots averaged 956 FPS, and the Federal HST +P 124 grain averaged 1195 FPS. Similar to what C. E. Harris experienced in the article though, my 940 will display hard extraction with most anything other than standard pressure ammo. I had a Blackhawk convertible that absolutely required dry chambers, or it would bind up with even standard pressure ammo. Drying the chambers resolved the issue. Got to try drying the chambers of the little 940 next time out...

    FWIW, unlike the 940, my Ruger Sp101 9MM functions without issue with any and all 9mm ammo I've ever tested in it, to include NATO, +P, +P+, etc. The SP101 just works.

  9. #9
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    A couple of extra data points.

    All 9mm shot was not +P.

    The reference to "Airweight" J frame should have said Scandium. I've found I can tell the difference in felt recoil between the two and should not have used the term interchangeably.

    I may try the 940 with bigger grips next time but the laser sure is helpful when dealing with the 940's less than ideal sights.
    My apologies to weasels.

  10. #10
    Has anybody tried having the chambers honed? A common procedure on competition nine-shooters.

    There was a 940 around here that had been cut for 9x23 - .38 Super, still usable with clipped 9mm P that the seller said extracted freely.
    Code Name: JET STREAM

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