S&W J frame vs. K frame


April 15, 2009, 11:56 AM
Aside from capacity, what are the differences between the J and K frames? More specifically, is the length of pull of a J frame shorter than that of a K frame?

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April 15, 2009, 12:14 PM
Yes, smaller gun all the way around.

LOP, measured straight back from face of trigger to rear of grip frame:
J = 2 7/8".
K = 3 1/4".


April 15, 2009, 12:18 PM

Excellent, thanks!


Do you know if there's a difference in the stock trigger pulls?

April 15, 2009, 12:26 PM
That's really hard to generalize about, when guns have been made for over a century, using different materials, for different purposes, etc.

However, I'll be stupid and try...

My K-frame is VERY smooth in DA mode, light and crisp in SA. It's a regular old Model 10, but a relatively old one (10-5).

My recent-production J-frame (DAO), bone stock, feels a lot better than I expected it to feel, but there's more of a "mechanical" feel to the pull. I have read that this is an artifact of the smaller internals and shorter lever arms that entails. It's good enough for me to keep 'em in a pie plate at 25 yards, DA, with stock sights, in poor light. Not bad, and totally adequate -- feels at least as good as DA in some full-size Colts I could mention. However, it doesn't feel buttery like the 10 does.

April 15, 2009, 12:27 PM
How about if you narrow it down to current production, like a new 60 J frame vs. a 67 K frame?

April 15, 2009, 12:30 PM
Can't say. Don't have 'em.:)

Take some snap caps to the store.

My guess, though, is that caeteris paribus the larger gun will inevitably feel a tad smoother due to the factors I mentioned above.

Jim K
April 15, 2009, 12:31 PM
One major difference today is that the K frame still uses a flat mainspring, while all J frames use a coil spring. Some folks feel the flat spring gives a better trigger pull.

Most small revolvers require a strong mainspring because primer ignition requires a certain momentum. Momentum is mass times velocity, so if the hammer is smaller and lighter, its speed must be increased by using a strong spring.


April 15, 2009, 12:33 PM
Jim- do L frames still use the flat spring?

April 15, 2009, 12:35 PM
The principal difference in trigger "feel" is:

The J-Frame uses a coil mainspring.
The K-Frame uses a flat lief spring.

There is more "stacking" with the coil spring then with the lief spring.

And like Armedbear said, the J is smaller and just doesn't have as much leverage on the internal parts.

But, for the intended use of close range SD, the J works just fine!

If you want a fine trigger pull for utmost accuracy, cock it and shoot it single action.
When you do that, there is no difference between them.

All J frames use a coil mainspring.
All K, L, N, and X frames use a flat mainspring.


April 15, 2009, 12:51 PM
Well, now, if you have a long coil spring so you only compress it partially, I don't think you'll necessarily have excessive stacking.

Of course, you'd have a hard time doing that and fitting it in a J-frame.:)

And if you have a crappy leaf spring, it can still feel like ****. I've got a nice crappy one from a Colt clone in my toolbox.

S&W must use decent leaf springs.

April 15, 2009, 01:03 PM
Another complication in the "J" vs "K" trigger skirmishes is that the hidden hammer "J"s don't have the hammer block common to the other models thus making the hidden hammer models a teensy bit smoother.

Or at least as much smoother as is associated with the "toss the hammer block" overboard portion of the old fashioned shadetree trigger jobs.

Got the above from Grant Cunningham's blog but don't have a link handy.

April 15, 2009, 01:13 PM
Of course, you'd have a hard time doing that and fitting it in a J-frame.No, but Wolff makes some reduced power spring kits that sure will slick up a J-Frame trigger.


S&W errors on the heavy side to insure 100% reliability with hard primers, dirty guns, or after 100 years of use.

You can install a reduced power main & rebound spring and really make a better trigger on a well maintained gun.

I used to do a lot of that, but more recently just leave them alone.
S&W's logic makes a lot of since when you think about it!


April 15, 2009, 06:23 PM

I'm not planning on using the 642 for NRA 2700 matches any time soon.:D

S&W does offer a slicking-up too, but it's not cheap, considering that my gun meets my expectations now and as I said, it's no match gun.

April 15, 2009, 07:30 PM
The Wolff springs work wonders. But I'd suggest not going that route in a carry revolver. I love them in my 66 but the J's coil need the impact. My 60 J is no longer my carry so I have them in it. They work perfect. But my 442 is bone stock and I won't change them. It's my carry now and I don't see the need to lighten the pull. It's already sweet and why do you want a light pull in a ccw?

April 17, 2009, 12:30 AM
The most improvement I have been able to accomplish on my J Frames actually has to do with the rebound block.

The spring hole in the block of all of the J Frames I have opened up (at least 10 examples) looks like it was bored with a dull rasp. Polishing this hole helps the trigger in two ways. It smooths the pull and it allows a reduced power (2-4# lighter than stock) rebound spring to be used.

I bought a flex hone for the first ones I did (expensive). Later I discovered that a wool bore mop and JB Bore Paste driven by an electric drill worked as well. The idea is to get the "screw thread" surface reasonably smooth - not to get a mirror polish. You can feel when the resistance to the tool reduces.

The second trick I discovered is to screw the rebound spring on to a tight fitting drill bit and polish the outside with 240 grit carbide paper until the coils are slightly flattened. This allows the coils to slide over the remaining roughness in the spring hole much more smoothly.

Just these changes with a full power mainspring produce a marked improvement in the trigger without compromising reliability.

Finally, use a good synthetic oil sparingly and shoot about 500 rounds to break everything in and prove reliability both of the gun and the shooter.

Low Budget Shooter
April 17, 2009, 01:21 AM
Dear marklbucla,

I have been practicing with a j frame and two k frames. I am not an expert on the inner works like some of these guys are. But as for the shooting experience, the k frame is just easier to shoot well overall. I have relatively big biscuit hooks, and the k frame feels just right.



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