It's my understanding through reading various articles and posts that S&W developed the L Frame revolver so they would have a frame that would be stronger, and hold up better, while firing full strength .357 loads. That all sound well and good, but after comparing my L frame guns (586, 686, 581, etc.) with my K frame guns (19, 13, etc.) the dimensions seem to be the same (disregarding recessed vs. non-recessed). I know the stocks are interchangeable, but I just can't find a noticeable difference in the dimensions of the two frames. I know I must be missing something, but I don't know what it is. What is the difference?

Sir,

The main difference lies, I believe, in the larger diameter of the L-frame cylinder, which permitted the elimination of the thinner, flattened portion at the bottom of the K-frame's forcing cone. This is where the K-frame magnum is vulnerable to cracking, according to those who are familiar with the problem.

Others will provide a more accurate description, I'm sure.

Andy

Quit looking at the rear end of the frame and look at the barrel threads, and the frame where the barrels screws in. Measure the diameter of the cylinder. A fraction of an inch in hardened steel is significant.

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Science plus Art

The principal areas of difference between K and L Frame guns are: Barrel shank and frame lunette are slightly larger in diameter, cylinder is larger in diameter and the charge hole radius is greater, frame window is taller for the larger cylinder, and the charge hole walls are thicker.

All these differences are easily determined with a dial caliper. If you are trying to measure with a steel scale (ruler) they aren't quite so obvious. Try to put an L Frame gun in a fitted holster for a K Frame and you will see there is a difference.

If you have measured the two guns with a dial caliper and there is no measurable difference then you are measuring either two K Frame or two L Frame guns, not a K and L.

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Gunsmithing since 1961

Sometimes a side-by-side comparison comparison may be helpful, at least visually....

The frame size difference appears very minimal between the K and L but it is apparent with the different cylinder sizes if we look closely at them next to each other.

I believe most people would agree the L frame certainly feels more substantial in the hand even if a visual doesn't doesn't clearly portray it...

Hope this helps..

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Terry

I agree with TDC. While the dimensional differences are slight, the L frame just "feels" like a bigger gun. Here's some more photos showing a 686 (L frame) on the left, and a 66 (K frame ) on the right. The L frame has a full underlug, larger cylinder, and slightly beefier frame window. I'm sure if I were handed both, blindfolded, I could tell them apart from the weight and balance alone.

The L frame is just "beefier", I've never had a problem telling the difference visually.

Attached Images

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I appreciate the in-depth discussion of the differences. When I posed the question last night I had a 581 (no -) and a 13-2 sitting in front of me, and measured with an electronic caliper several areas on the two guns, and many of them were the same. This morning I see the most obvious difference is the diameter of the cylinder ( approx. .1") and the size of the barrel at the forcing cone, along with the increase in the size of the area where the barrel screws into the frame. For me, this forum is a learning tool, and the learning continues. Thank you.

Here is photographic evidence of the most important difference between the venerable K frame and the newer L frame.

The 686 on the left has a thicker, fully circular forcing cone allowed by the modest increase in frame height above the cylinder centerline. The 66-3 on the right shows the classic flat bottom cut on the forcing cone.

Very good illustration. Note also the added thickness of the frame above and below the forcing cone.

Great thread with some great pics!

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NRA Certified Instructor