Is the 67 and 66 the same gun except for the chamber of the cylinder? Or are there other differences? Can a 67 safely be converted to a 357mag?

I don't plan on doing it, just curious.

Thanks,

Rosewood

No and no.
Well, let me rephrase. The 67 is built to be a .38 Special. The cylinder is the proper length and the barrel extends into the cylinder window to meet the cylinder. The 66, on the other hand, has a slightly longer cylinder to accept the longer .357 cartridge, and the barrel extension is shorter.
You could convert it, but it would require either a new barrel plus cylinder or a cylinder and the barrel cut at the forcing cone end and the cone re-cut. Easy enough for someone with the proper skills and tools, not so much for most others.
A while back, I had a Model 10 converted by a gunsmith from a 4" 38 to a 3" 357. It works fine, but I seldom if ever use 357s. The reason for my conversion started out as barrel only but got a little carried away. Long story.

The Model 66 also has the ejector shroud that a 67 lacks.

The .357 Magnum chambered Model 65 is a closer match for the Model 67.

I knew that about the shroud. But there are 357 chambered guns that don't have the shroud.

I thought the 65 has fixed rear sight and the 66 has adjustable like the 67?

Rosewood

So, the frame is the same, the difference is the barrel and cylinder then?

When I measure the cylinder, it appears that you could ream the cylinder out to 357 mag. Chambered rounds would be awfully close to the end of the cylinder however.

Rosewood

Correct, new cylinder/yoke assembly (the model 66 has a longer yoke than the 67 so just the cylinder swap won't work), barrel either swapped or the forcing cone shortened from .38 to .357 length, frame lug modified for the longer cylinder.

The 67 barrel and frame may have the same strength as the 66, but I would not be so certain about the cylinders. I would not want to personally find out the .38 cylinder is not rated for the 100% pressure overload from using .357s.

Or you could just buy one on which the factory did all the modifications for you.

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Alan
SWCA LM 2023, SWHF 220

Murphydog answered correctly, but since you quoted me....
The cylinder does appear to be able to "accept" 357 cartridges if it's reamed. Some have done it, from what I read here and there. But that old bugaboo: "Is it SAFE??" pops up when you talk about something that may blow up on you.
I'm all for conversions and mods, as I've either done some or had some done for me, but I stay away from doing anything to the cylinder just for that reason. With the availability of parts made for the purpose still reasonably good, I'd go looking. One of my favorite sources is Smith and Wesson Revolver Parts & Pistol Parts For Sale – USA Guns And Gear-Your Favorite Gun Parts Store They regularly have good parts at reasonable prices.
I know you said this is an academic exercise and I personally appreciate what you're saying. Always fun to plot a "What if?" to see if it would really work. Take care and Happy Shooting!

WHY? would want to do that to a 67? Bob

With enough money, anything is possible. It's not a cost effective conversion given existing factory made alternatives.

I guess the tapered barrel 67 would be a bit lighter sans the heavier barrel and ejector shroud. Sort of a .357 K-frame Mountain Gun.

The only reason to do it would be because you really wanted that sort of a configuration and there's no other way. You'll never get that money back if it's ever sold. These sorts of things are best done to guns your heirs will have to deal with after you've shot them for decades. In that scenario cost is irrelevant.

Think before I did that, I'd handload something on the order of duplicate .38-44 cartridges. (158 gr hardcast LSWC or LSWC-HP's @ ~1200 fps).

Load those a lot for my .38-44 HD, use them in other .357's and have shot them in M10 .38's.
In field performance, I daresay there's not much difference between them and OTC .357 ammo, other than if the desire is light/fast JHP's.

__________________
Ret'd LEO
SWCA #2275

I knew a buddy who ordered a .357 Mag. Ruger Security Six with trigger job from famous pistolsmith Jim Clark, Sr. After talking it over with him, Jim provided a .357 Mag. Ruger Security Six that was a reamed out .38 SPL. It had a sweet trigger job! Some folks think the Security Six guns are more durable than K frame Smiths.

If you'll compare the thickness of top strap of a Ruger Security Six to that of a K-frame, you'll see the difference, you won't have to measure it. Many years ago, I carried a Security Six Stainless as a police duty gun, as the cost and availability of a Model 66 was beyond my means. I still have that Security Six and trust it today to shoot full power .357 Magnum ammunition.

The Security Six series was a fantastic line of revolvers and it’s entirely possible that they are “stronger” than a S&W K-frame but… not sure how we would know or how we might find out in typical use and even if they are, it isn’t going to be because of the thickness of it’s investment cast frame versus S&W’s forged frame.

Interesting. Tell me more.

Rosewood

Top strap thickness had nothing to do with it.

The problems were going out of time and split forcing cones.

The Border Patrol ran a test in 1985 of 2 Model 65s vs 2 Service Sixes. The Rugers did outlast the Smiths by a considerable margin.

The S&Ws didn’t experience any catastrophic failures, not even a cracked forcing cone. They were deemed “no longer serviceable” by the armorers.

Bear in mind that much of the K-frame’s bad rep occurred in an era when the SAAMI spec for the .357 magnum was 20% higher than today’s. It was changed some time in the early 90s.

The Six Series was designed around the .357 magnum cartridge. The K-frame wasn’t.

I don’t know why this question about converting K-frame .38s to .357 ever comes up, but it does for some ridiculous reason. If the OP wants a .357 with a lighter barrel, find a Model 67 barrel and have it installed on an M-66. I can’t imagine a sane gunsmith converting a K-frame .38 to .357.

Yes, the two are built on a frame of the same dimensions. But there’s no guarantee the alloy or heat-treat are exactly the same, no matter what your cousin heard from a guy who worked at Smith & Wesson 25 years ago.

According to Dr Roy Jinks, the S&W historian and longtime S&W employee (retired), the magnum revolvers received a different heat treatment vs. the non-magnum revolvers.

As stated, the Ruger Six revolvers were designed around the .357 Magnum cartridge. Their .38 special and .357 Magnum cylinders were identical, except for the depth of the chambers. Ruger chambered their Six series revolvers in .38 special for those customers who did not want .357s.

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John 3:16
WAR EAGLE!

Instead of modifying a 38 Special revolver, trying to turn it into a 357 Magnum, why not sell/trade it and buy a 357 Magnum revolver?

__________________
VCDL, GOA, NRA

I wouldn't worry about the frame. I would have a small degree of concern about the cylinder. I find it hard to believe any modern frame received a inferior HT when it would be no more trouble or cost to HT them all the same. But that aside consider the model 360 scandium alloy J frame 357s. They are built on a smaller, lighter, frame of scandium alloy which has a tensile strength of 350 MPa and the yield strength of about 280 MPa. Where 4140 steel has a tensile strength of 655MPa and a yield strength of 415MPa straight from the mill. In other words a NON heat treated 4140 frame is almost twice as strong as any scandium frame. Same applies to the N frame alloy guns. I have J, L and N frame scandium guns. They are dimensionally the same as my steel ones. Where are the blown up scandium frames??? Obviously the frames do not need nearly the strength of 4140.

Top strap? While they are a great addition and necessary with modern rounds look at the construction of the fairly powerful Colt dragoon. It could fire a 144 gr 44 caliber ball at 1200fps and didn't even have a top strap, and the barrel was held to the frame with a wedge. .

BTW on Titanium you have to go to the highest grade (and cost) alloys to achieve the same tensile and yield strength as 4140

More than one K 38 cylinder has been reamed to 357 and not blown up. Plus quite a few 38 cylinders have been reamed and cut to fire 9mm which are about the same pressure as 357 and end up with less metal at the stop notch from the reaming. Where are the blown up guns or even the reports of them???

But, model 19, 13 and their stainless counterparts are not hard to come by. It is also not hard to face off the barrel extension and recut the forcing cone on a 38 special revolver so one fits.

It is even easier and unless you have your own shop and skills less expensive to just trade your 38 on a 357 or buy one.

I have 2 38 cylinders I reamed and cut to 9mm which I have fired repeatedly, but only because I chose to have a a gun that could fire 9mms.

I also reamed one K38 cylinder to 357 and fired some 357 rounds though it. I did that some time ago, but decided it was better to go with factory 357 cylinders so it sits in my parts pile another experiment.

I feel exactly the same way about cylinders.

It defies modern mass production for S&W to have different processes in place for K-frame .38 Special cylinders and K-frame .357 Mag cylinders.

The very suggestion or idea of this slows production.

Long ago, in the '70's I worked p/t at a large LGS that had been in-place a long time.
Do recall the owner, who'd been in the business a LONG time occasionally lengthening the chambers of a M36 to accept .357 for certain customers he knew well.

The idea was not for it to regularly fire .357 ammo, but in order to have another ammo option in a worst-case scenario.

Talked to a few guys that had it done - they each related zero problems firing a few .357's, but of course it was not much fun for the hand(s) gripping the gun, especially with standard J frame Magnas.

__________________
Ret'd LEO
SWCA #2275

My thought exactly, now before they started making them in 357 mag, maybe so, but once the mag was in production in that frame, it would make the most sense to make them all the same to the required specs for the worst case scenario.

Rosewood

Now this makes sense. Using actual numbers and specs instead of speculation.

Rosewood

I don't see how it slows production, if it's a step that's eliminated.

Let's say you can heat treat 100 cylinders a day. Why heat-treat .38 cylinders? You've limited your .357 production by however many .38's you're doing which raises the unit cost of the .357 cylinders. You've also delayed the .38 production by the amount of time the heat treatment takes.

Not to mention that nothing is free. Heat treatment is then a cost that's now added to the .38 cylinders.

If they are heat treated after machining the .38's and .357's are already sorted so there's no added cost for sorting. If they are machined after heat treating there's the extra wear on machine tools from the unnecessarily hardened steel of the .38 cylinders.

It may not be much more expensive to just do them all, but it for sure is not cheaper or faster in my view if you look at it from the perspective of the production time and cost for the two calibers individually.

If you heat treat the cylinders post machining you will have some degree of dimensional shift. Heat treating reforms the shape of the steel's internal structures which effects their shape. If I took a perfect cube or sphere of 4140 hardened it and then tempered it, it would not longer be a perfect cube or sphere. If i drill and ream say a .250 hole in a piece of tool steel then harden and temper it, a .250 pin gauge will not go in the hole post HT. Been there done that. Exact same thing would happen to a cylinder. There is absolutely no reason than the cylinder material could not be HT as long lengths of round stock. Then there is no need to track which got treated and which did not PLUS, a big drop in liability. If a 38 cylinder blew up for any reason it would be possible for S&W to be held liable for failing to use best possible method to insure safety.

The wear on additional machinery would be near zero as it is not at all about hardness. I have a hardness tester checked some frames and both 38 and 357 cylinders and they are the same hardness are the frames. In fact after checking them in Rockwell C scale I went to B scale to get more accurate readings because they were all so soft, in fact around 102-4 Rockwell B. Which is around Rockwell C26 and not very hard at all. Mild steel is softer but not by that much. A poor knife soft blade would be RC56.

It is NOT about hardness with cylinders and frames it is about tensile strength and yield strength. A fully harden cylinder would be a shrapnel bomb

I actually studied metallurgy, Heat Treating and even have my own oven.

What ^^^ said.

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Pine_Worker
Ex-LEO, NRA Life

The 67 is a pleasant gun to shoot.......with .38 Spl +P ammo, which I shoot in all my .38 Spl. guns, and in my M-66-1 2 1/2" .357. It's plenty strong enough for me, and not as expensive as .357.

The frame and forcing cone was made to shoot .38's, and using .357 ammo constantly in it can cause excessive wear, and cracks in the frame. S&W recommends using .38 Spl. in the 66, mostly......357 only occasionally. BobK