S&W 66-7 Two Piece barrel question

The newer model 66 now incorporates a two piece barrel. Does this in any way lessen the propensity for forcing cone cracking.

I don't think it would make any differece as the problem comes from the cylinder size and the clearance cut at the bottom of the barrel. That's probably why the went to the L-frame size when they replaced the 65/66 with the 619/620, to get a full size forcing cone all the way around the barrel.

Two Piece Barrel

Thanks Handgunner, What is the alleged purpose for the two piece barrel, is it cheaper to produce, easier to service or possibly stronger. I know about the MIM parts like the hammer and others, but since the model was being phased out why make such big changes?

DRADW said:

Thanks Handgunner, What is the alleged purpose for the two piece barrel, is it cheaper to produce, easier to service or possibly stronger. I know about the MIM parts like the hammer and others, but since the model was being phased out why make such big changes?

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The purpose of a tensioned barrel is not alleged. It is to improve accuracy. This has been proven time and again over the last four decades.

Again thanks for taking the time to reply. Maybe alleged was too strong a word.

The purpose of the two piece barrel is cost savings.

The old barrels started off as a rough lump of forged metal.
In the older barrels, even the front sight was part of the forging.
The bore was drilled and rifled, and the outside was machined and threaded.
If anything went wrong at any step, the barrel was scrap and all the previous cost of work was lost.

The new barrels have inner tubes that are rifled and threaded.
Modern high speed turning equipment is used that seldom makes a mistake.
The outer shroud can be a cast part that's virtually finished when it comes out of the mold.
If the shroud is less than perfect, it can simply be re-cast.

Fitting the barrel is much faster and easier, since the shroud is just slipped onto the frame and the inner barrel is tightened in place.
The old one-piece forged barrels required extensive hand fitting and adjusting.

So, the new barrels are much faster and cheaper to make, and require little hand work or fitting. Human labor runs the price up, so anything that can be done to limit that costs less.

Dfariswheel
That was very informative, my compliments on your knowledge. I happen to really appreciate S&W revolvers. I don't think the older pistols, although excellent considering the manufacturing abilities that were available at the time, I think we have better more precise weapons available now. I've never worn out a quality handgun, and hopefully I'll never need a super capacity semi auto. The explanation of the production methods concerning barrels will stay with me. My 66-7 Is beautiful and utilitarian. What more can you ask for.

dfariswheel said:

The purpose of the two piece barrel is cost savings.

The old barrels started off as a rough lump of forged metal.
In the older barrels, even the front sight was part of the forging.
The bore was drilled and rifled, and the outside was machined and threaded.
If anything went wrong at any step, the barrel was scrap and all the previous cost of work was lost.

The new barrels have inner tubes that are rifled and threaded.
Modern high speed turning equipment is used that seldom makes a mistake.
The outer shroud can be a cast part that's virtually finished when it comes out of the mold.
If the shroud is less than perfect, it can simply be re-cast.

Fitting the barrel is much faster and easier, since the shroud is just slipped onto the frame and the inner barrel is tightened in place.
The old one-piece forged barrels required extensive hand fitting and adjusting.

So, the new barrels are much faster and cheaper to make, and require little hand work or fitting. Human labor runs the price up, so anything that can be done to limit that costs less.

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Having spent nearly 30 years as a Manufacturing and Design Engineer I'll dispute your claims. The fact is that on the surface the 2 piece barrels APPEAR to have a cost advantage. However, when you factor in the quality requirements in terms of fixturing, inspection, record keeping, stock tracking, and inventory control, you'll probably find, as I suspect S&W has, that making 2 precision parts costs more than making one precision part even if the one piece part requires a bit more fitting. I suspect that's the reason why every single steel K & L frame that featured a tensioned barrel has been dropped from the catalog, they cost more to make that initially thought. The only remaining tensioned barrel S&W's are the Scandium models and I believe the 460 and 500 Magnums, all of which cost far more than the 66, 67, or 620's did when they were being made with tensioned barrels.

As for the accuracy benefit of the tensioned barrel, do a bit of reading on the accuracy of the Dan Wesson line of revolvers, almost all of which used a tensioned barrel. In addition, take a look at Guns & Ammo's testing of the M&P R8. They mounted a scope on one and shot a near 1/2 inch group at 50 yards from a bench rest using off the shelf Commercial SD ammo. I've personally managed to group my 620 to 1.75 inch at 35 yards and if I were to mount a scope on it could probably get it under an inch on one of my good days. Simple fact is that tensioned barrels are more accurate.

As for the OP's concern, as previously noted the K frames have that flat machined to clear the gas ring on the cylinder. Because of this, it's best to consider that the weak point in the design and treat it as such. On a positive note, what you have is a really superb 38 that can occasionally be used with the 357 Magnum if you limit yourself to 158 grain loads.

There have been some reliability issues with the two-piece barrels in the newer series 67's. Do a search on it on this forum.

Scooter,
I can guarantee you that S&W did not try the two-piece barrels for improved accuracy.
They are, as D said, strictly a cost-saving proposition.
S&W is moving away from those barrels to a degree & has dropped at least three models that used them.

I've seen photos of the flange broken off at the muzzle & of the rear end broken off at the threads.
I would suspect the discontinuance of the Model 67 & 64 with two-piecers was due to failures encountered with the system, more than anything else.

S&W has modified production methods to eliminate as much of the human touch as possible in revolver assembly. The two-piece barrels are a part of that business plan.

Those who point out that tensioned barrels CAN be more accurate CAN be correct, IF the method used is done correctly. The Dan Wessons were famous for their tensioned barrel accuracy, but those used a quite different system.
Denis

I've seen the posts about the cap failing on the tension barrel and I've also seen posts about one piece barrel shearing off at the frame. IMO the cause in both cases is simply bad metalurgy in those particular barrels. Basically, stuff happens and S&W cannot afford to x-ray inspect every single bar of steel they use and we couldn't afford the guns if they did do that.

However, I do find it odd that that nobody seems to remember that cantelever mounted barrels have been snapping off at the frame of revolvers for over 100 years but everyone wants to blame the "new" system for a few isolated failures. Wasn't too long ago that a member posted images of the 686 that he shot the barrel off of. It snapped off right where any Engineer would expect it to, at the stress riser created by the transition from the mounting extension to the full profile.

As for the accuracy benefit of the tensioned barrel, I've seen it first hand. I have 3 revolvers equipped with reflex sights that I shoot an longer ranges with and the 620 is clearly the most accurate. Unfortunately it also has the most recoil so I'm still working on shooting to it's potential.

handgunner356 said:

I don't think it would make any differece as the problem comes from the cylinder size and the clearance cut at the bottom of the barrel. That's probably why the went to the L-frame size when they replaced the 65/66 with the 619/620, to get a full size forcing cone all the way around the barrel.

Click to expand...

The 66-7 does not have the clearance cut on the bottom. Here is my 66-7.

A while back I worked with a two-piece Model 67.
Accuracy was no better or worse than other Smith .38s I've shot over the years.

OK, but nothing remarkable.

And it's not a cap, it's a flange.
A cap implies a different type of separate part.

Denis

"I've seen the posts about the cap failing on the tension barrel and I've also seen posts about one piece barrel shearing off at the frame. IMO the cause in both cases is simply bad metalurgy in those particular barrels. Basically, stuff happens and S&W cannot afford to x-ray inspect every single bar of steel they use and we couldn't afford the guns if they did do that."

There appears to be more to the two-piece barrel problems than just a bad barrel or bar of steel.
As I recall a number of guns purchased by an East coast prison system suffered a number broken barrels in Model 64's.
There have been a number of other verified reports of barrels breaking off, and flanges failing.

To be fair, these seemed to be from early production guns made when the two-piece barrel was still new.
I'm rather surprised no company or custom gunsmith has brought out a Dan Wesson-like interchangeable barrel system for the new S&W revolvers.

D,
Considering the relatively lackluster sales of the On Again/Off Again DWs over the years, there probably would not be much money in the idea.
Denis

Srigs said:

The 66-7 does not have the clearance cut on the bottom. Here is my 66-7.

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How would the 2-piece barrel allow them to eliminate the clearance cut like that, unless the entire forcing cone is thinner instead of just the bottom?

As I understand it, the clearance cut is to allow space for the crane to get into place, going to a 2-piece barrel shouldn't change that.

Confused...

Gearhead Jim said:

How would the 2-piece barrel allow them to eliminate the clearance cut like that, unless the entire forcing cone is thinner instead of just the bottom?

As I understand it, the clearance cut is to allow space for the crane to get into place, going to a 2-piece barrel shouldn't change that.

Confused...

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Everything I have found says it was part of the -7 engineering change. The picture posted shows it. My 3rd gen of S&W book from 2006 does not even show a -7 engineering change and the one shown based on serial # is 2004-5 vintage.

My 66-7 does Not have the forcing cut relieved at the bottom.
This has been the most informative post I have ever experienced,
The knowledge I have gained and the respect I have for members of this forum is awesome. I'm proud to be a member, thanks guys.

It's all due to the IL and MIM parts. You see, a gun when fired sets up a resonant frequency. With the hole in the frame, that resonance gets corrupted, sending a shock wave back through the barrel. The forged trigger and hammer used to buffer that shockwave but then they put in the MIM parts ...

Dag-nabbid new-fangled gadgets will be the end of us, I tell 'ya ...

Srigs said:

Everything I have found says it was part of the -7 engineering change. The picture posted shows it. My 3rd gen of S&W book from 2006 does not even show a -7 engineering change and the one shown based on serial # is 2004-5 vintage.

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We know it was part of the engineering change, but what was it in the change that allowed them to eliminate the cut?

blujax01 said:

It's all due to the IL and MIM parts. You see, a gun when fired sets up a resonant frequency. With the hole in the frame, that resonance gets corrupted, sending a shock wave back through the barrel. The forged trigger and hammer used to buffer that shockwave but then they put in the MIM parts ...

Dag-nabbid new-fangled gadgets will be the end of us, I tell 'ya ...

Click to expand...

Cute. I wish it were true...