What the difference in strength between different K-frames?

[daveboy]

Okay, dumb question time. I just got a 10-8 and I was thinking of loading up some +P rounds for it. It will
Live a life of luxury, with mild.38 loads, but I’d like to try some +P in it. I see +P rounds with pressures in the 19K range and that kinda scared me. Then, I remembered that my Model 19 fired .357 Magnum. I know all about the cracked forcing cones and all that, but still the revolver was good for occasional, full-house .357 loads.
My question is this: My Model 10 and Model 19 both have the same frames. To my knowledge, their internals are identical. Their cylinders are the same diameter, with the same amount of steel between bores. The barrels are the same. The cylinders are slightly longer on the 19, but that shouldn’t affect strength. So, why is the Model 19 okay for .357 Magnum pressures, but same vintage Model 10s are not?

 

[steelslaver]

First of all I would not consider a 10-8 "vintage" next, I would not hesitate to fire +P in one or any other steel K frame 38 special. Plus, I have made a 10-7 into a Smolt by machining the frame for sights and installing a model 19 cylinder and a Python barrel with no issues.

 

[MajorD]

Both are fine for plus p. If you wear out your 10-8 from plus P it will take 500 rounds a month for a few decades. The heat treat was different between the 10&19, but no concerns.

 

[JP@AK]

Don't forget that more than 1,000 Model 10-6 revolvers were chambered for the .357 Magnum in an order for the NYSP. These were the forerunners to the Model 13-1.

 

[s&wchad]

My question is this: My Model 10 and Model 19 both have the same frames.

It may be a relatively safe conversion, but they're not the same. The front of the Combat Magnum frame was made slightly larger compared to a regular K frame.

I swiped a couple photos off the internet that illustrates the difference.

 

[stansdds]

You will wear out a K-frame 38 Special by shooting +P ammo through it. It will take tens of thousands of rounds, but I'm sure you could wear one out.

 

[steelslaver]

My measurements don't show any difference on the later frames

 

[s&wchad]

My measurements don't show any difference on the later frames

That may be true for CNC frames. You can see the difference in the '70's vintage guns I posted (10-5 and 19-3). The 10-8's still had this same frame.

 

[Chuck Edwards]

I've noted here before that I have two K frames (10-8 and 67-1) that I used when I was an active IDPA competitor, which each have thousands of +P-level handloads through them with no ill effects. If you occasionally shoot +Ps through your K frame, it'll still probably outlive you.

 

[steelslaver]

I just measured a 19-3, a 15-3 an 18-4, a 10-6, a 10-7, a 10-2 and a pre model 10 5 screw w 2" barrel and they were all within a couple thousands of .825 wide and .620 long where the barrel threads into the frame. I did find an earlier 32-20 that was only .810 wide. The measuring of the height would require removing the sight so didn't check that. But one with adj. sights would be weaker than a fixed sight gun due to the material that is removed to fit the sight, both down the top strap and at the back where a decent chunk of steel is machined away for the sight body.

 

[daveboy]

First of all I would not consider a 10-8 "vintage" next, I would not hesitate to fire +P in one or any other steel K frame 38 special. Plus, I have made a 10-7 into a Smolt by machining the frame for sights and installing a model 19 cylinder and a Python barrel with no issues.

I wrote "same" vintage... Meaning the same age as a Model 19.

 

[daveboy]

It may be a relatively safe conversion, but they're not the same. The front of the Combat Magnum frame was made slightly larger compared to a regular K frame.

I swiped a couple photos off the internet that illustrates the difference.

View attachment 771413
View attachment 771414

I'm not converting anything. Just curious what the difference is. I'm looking at my 19-4 and my 10-8. They appear identical except for the slightly longer cylinder of the 19.

 

[daveboy]

My measurements don't show any difference on the later frames

I didn't measure, but to my eyeballs my 19-4 and 10-8 are identical except for the slightly longer cylinder on the 19. So, I'm left to believe that the difference is either in the metallurgy or marketing.

 

[daveboy]

That may be true for CNC frames. You can see the difference in the '70's vintage guns I posted (10-5 and 19-3). The 10-8's still had this same frame.

I can't see any difference.

 

[steelslaver]

Yes, the magnum cylinders are about 1/10" longer and the magnum barrels have 1/10" shorter barrel shank. Same size window. You can install a model 19 cylinder on a model 10 yoke (as long as both have the same style gas ring., you can even use a 38 special barrel if you trim the shank to get the correct B?C gap and redo the forcing cone. In the past lots of K38 cylinders were reamed to 357 mag. I have not heard of any blowing up and OI would expect reports of that to show up here, but they don't. I would won't ream a 38 cylinder to 357, but mostly because for me it isn't that expensive to fit a factory 357 cylinder. I find them al the time for $50-60 on Ebay, Same with barrels. But consider this, TKC will machine a K38 cylinder to use 9mm in full moon clips. The 9mm has a wider base (,391) than a 357 (.379) and that is right at the cylinder stop notch area. The 9 runs at 35,000psi and the 357 at the same 35,000psi.

I am not advocating running a 38 special cylinder at 357 pressures or reaming one to 357, just stating what I know to be true. I have reamed a coupe 38 cylinders to 9mm and recessed them for moon clips, Mostly because I can and someday one of them may be useful. At this point 9mm ammo is more plentiful than 38. But then I now have 3 9mms in 1911 style semis.

 

[budhall]

First of all I would not consider a 10-8 "vintage" next, I would not hesitate to fire +P in one or any other steel K frame 38 special. Plus, I have made a 10-7 into a Smolt by machining the frame for sights and installing a model 19 cylinder and a Python barrel with no issues.

When you build a Smolt, do you do anything to add a forward stabilizing feature?? Ball &:detent perhaps?? I assume that since the Colt barrel lug channel is different than the S&W ejector rod center, a center stabilizing pin wouldn't be realistic, would it??

 

[s&wchad]

I know I read about the frame differences, so I looked it up in the SCSW. This is in their description of the Model 19:

The Model 19 is built on a frame that is slightly larger than a standard K frame in the yoke area.

Notice how the thick area where the barrel threads in extends down to the bottom of the shroud. The thick area on a standard K frame angles back just below the ejector rod. As I said, the frames are not the same.

 

[steelslaver]

It would be possible to add a lug for the tip of the extractor, but you would be need a long set of drills and patience to do so. It is way easier to add a ball detent (or even 2 of them) in the yoke. But, the truth is a well set up S&W revolver will not cause the yoke to move out when rotating. The hand operates the ratchet at the rear of the cylinder very close to where the center pin is engaging the hole in recoil shield. Unless there is some drag somewhere there is really no reason for the yoke to spring out. But, I have installed a ball in both of mine.

A 15-3 made into a pinto Smolt.

PS I haven't been able t detect any improvement in accuracy with Colt barrels even using my machine rest.

 

[SS336]

In my mid 70’s 10-5? Sure, not a problem.
In my 1915 M&P? No I would not

 

[Model29-26.5]

It may be a relatively safe conversion, but they're not the same. The front of the Combat Magnum frame was made slightly larger compared to a regular K frame.

I swiped a couple photos off the internet that illustrates the difference.

View attachment 771413
I have not noticed this before.

So not all K frames are equal.
The Magnum K frame is different than the regular K frame.
There is a significant piece of info for people thinking they can make conversions.
Thanks for pointing that out.