Model 66 Ammo Question

[paperboy98]

I just got a model 66, and remember from other posts that I need to be careful with the ammo I shoot. What is the correct load to shoot, and why is the 66 this exacting? Thanks for all replies.
Paperboy98

 

[st regis]

Hello, Joe in GA here......no need to be particularly careful with your ammo choices. Plinking....any ol 38's are fine. For personal defense, the Federal 125 gr JHP in 357 magnum is still about a 96% one shot stopper- nothing else is really close in actual street shootings. A steady diet of the hot 357's might "wear it out" but I think the gun will handle anything in moderation. I carry a 2.5 inch 66 every day when I get off duty, (and take off the tupperware gun) loaded with the fed 125's.

 

[Jimmymac46]

Hello, Joe in GA here......no need to be particularly careful with your ammo choices. Plinking....any ol 38's are fine. For personal defense, the Federal 125 gr JHP in 357 magnum is still about a 96% one shot stopper- nothing else is really close in actual street shootings. A steady diet of the hot 357's might "wear it out" but I think the gun will handle anything in moderation. I carry a 2.5 inch 66 every day when I get off duty, (and take off the tupperware gun) loaded with the fed 125's.

Correct in every way. I think perhaps you are referring to an earlier discussion where the 110 grain magnums were in question. It has been argued that 110 grainers were short and as a consequence allowed burned powder to escaped from behind the bullet prior to it entering the barrel. This reportedly causes the frame above the forcing cone to 'flame cut' and damage the gun over a period of time. The suggestion was to not use 110 grain bullets in hot magnum loads. I have no other information regarding this problem and hope I am relaying it correctly. Perhaps others can add to or correct my information.

 

[Texas Star]

Swing out the cylinder and look at the thinner, flat portion of the barrel shank within the frame. That thin part is what usually cracks if the gun is fired much with 125 grain jacketed .357 ammo. The heat and additional ejecta from the cartridge case erodes the barrel shank (forcing cone), and in time, it MAY crack. By no means is this universal on K-frame .357's, but it is common enough not to shoot those loads in them a lot. The heavier bullets stay in the case until more powder burns, so less unburned powder and other debris hits the forcing cone, and the recoil impulse (to the gun) is different.

I asked engineers at several ammo plants and I asked S&W, and they ALL said that 125 grain and lighter .357 ammo should be fired in larger guns. NO .357 ammo should be fired as a REGULAR diet in K-frame .357's. They were intended mainly for use with .38 ammo, with maybe 10-15% of the ammo fired being Magnums. But the 158 grain bullets are much less destructive to the gun than light bullets. I asked about 140-145 grainers, and was told that they are so close to 158's that no one knows whether there is much difference in wear to the guns. It hasn't been studied. But the 140 grainers are certainly less abusive than the light bullets.

T-Star

 

[john traveler]

The S&W M19/M66 revolvers are fine guns in every category as stated. They were made in the many hundreds of thousands and served and continue to serve their owners as classy, potent, well-designed sidearms. However, note that S&W does not make K-frame .357 Magnums any longer, nor do they have replacement M19/M66 barrels.

The weakness, if it were to be admitted, is that the K-frame .357s have a thin spot at the 6 o'clock position of the barrel stub (forcing cone) which was machined to clear the cylinder gas ring. The sucessor to the M19/M66 is the M486/586/686 series which have both thicker and sturdier barrel stub w/o the machined flat spot.

The (not so theoretical) documented failures of K-frame .357 Magnums is that extensive firing of high-performance 110 and 125 grain .357 ammunition will likely lead to cracking at this point of the forcing cone. Numerous law enforcement agencies have reported this type of failure.
Standard and even +P .38 Specials don't seem to cause a problem, just the lighter bullet magnums.

Looking back a couple generations, before the model numbers were used to designate revolvers, and just after jacketed high-performance .38 Special ammunition was introduced in the 1960s, there were many documented cases of M&P barrels failing at the forcing cone. Yep, you guessed it: cracks or splits at the bottom of the barrel stub. S&W answer to that problem was to upgrade the quality of steel used in the barrel forgings.

 

[Texas Star]

John Traveller-

This is the first that I've read of M&P/Model 10 failures. Were those guns being fired with .38/44 ammo or hot reloads?

Where did you find that information? I am not challenging you; just want to get the full story on that.

It is true that S&W changed M&P steels and heat treatment about 1957, when Model numbers appeared. An S&W exec told Chic Gaylord, the famous holster maker, that they had made metallurgical changes then. Gaylord reported that in a 1960 book.

Of course, .357 ammo has far greater pressure and heat than any reasonable .38 ammo, so the K-frame Magnums, introduced in 1955, experienced the erosion and pressure problems more than did the .38's.

Thanks,

T-Star

 

[john traveler]

The M&P and K-frame .38 Spl problem with split forcing cones is well known to many police armorers that worked in the 1960s thu 1980s time period. S&W .38 Spl revolvers were still the department issued sidearm during this era and you can hear of the occasional split barrel breech. I was not a department armorer, but as a civilian gunsmith encountered a number of K frame split barrel stubs, including Combat Masterpieces, K-38, and M&P. This phenomenon was separate from the (not recommended) practice of firing .38-44 ammo in a K frame gun. I recall chatting with a gunsmith at the old Triple K gun shop back in the 1970s and he related rebarrelling K-frame revolvers for members of the police shooting range.

The problem, as I recall, did not happen when standard lead bulleted .38 Spl ammo was used, but when the high-performance jacketed stuff came out in the early 1960s. The Super Vel brand comes to mind.

 

[Texas Star]

Thanks. I recall Super-Vel, and it did seem pretty hot for a .38.

FYI, as a young lad, I asked S&W whether I could safely fire .38 High Velocity (.38-44) ammo in a Model 10. They told me that I could, but that doing so often would materially shorten the gun's life. Nothing was said about splitting forcing cones. I assumed that they referred to cylinder endshake and frame stretching.

At one air base, we were issued Hi-Velocity ammo (150 grain RN jacketed) for duty in our M-15 .38's,but qualified with wadcutters, so no harm was done. Good thing: we also had some Victory Models and older Official Police and Commando Colts.

T-Star

 

[18DAI]

Stay away from 125 grain 357's. Stick with 158 grain 357's, keep the barrel and forcing cone clean, and your grandkids will be enjoying that model 66.

I've yet to shoot a 66 loose, let alone bust a forcing cone. Sure, it happens, but not with any frequency. I notice when it does that the revolvers in question usually show lead build up around the forcing cone and have been shot with alot of 125 grain 357 and handloads.

Enjoy your 66! Regards 18DAI.

 

[shawn mccarver]

I just got a model 66, and remember from other posts that I need to be careful with the ammo I shoot. What is the correct load to shoot, and why is the 66 this exacting? Thanks for all replies.
Paperboy98

Shoot any 38 special you want and any .357 magnum of at least 145 grains that you want.

It has to do with flame cutting and erosion issues at the forcing cone when light (125 grain Magnums are used). 125 grain and lower specials are fine.

When introduced, the Model 19 and its stainless counterpart, the Model 66, were subjected to different uses than they were later. In the beginning, everyone practiced with 38s and carried 158 grain magnums.

Later, when the 125 grain magnums were introduced AND police and others started shooting such light weight magnums for practice as well as occasional familiarization, the issues started cropping up.

It is just not an issue at all if you use 38s for most shooting and just occasionally shoot the 125 grain magnums.

Feel free to shoot all of the 158 magnums you wish.

 

[deuterij]

Thanks

Some very good info here.

-E

 

[surveyor47]

This is reason we have L-frame magnums (586/686), which are designed for a full time diet of 357 Magnums.

Note that Ruger eliminated the Security Six, which was very comparable to the S&W K-frame Magnums, but with about triple the lifespan between servicings. They replaced the Security Six with the GP100, which is also designed for full time use with 357 Magnums.

Think of the K-frame Magnums as full time +P 38 Specials with a LIMITED ability to fire 158 grain 357 Magnums. Feed them 38s and they will have long happy lives, sort of like the dog food commercial.... Too bad S&W didnt give us that advice a long time ago. A lot of people got to find out the hard way.

 

[paperboy98]

Model 66 ammo

Thanks for all the great replies. As usual, I learned a lot from this board.
Paperboy98

 

[john traveler]

Back in the late 1970s to early 1980s before the trials and selection of the US M9 service pistol, the USAF conducted testing of various handguns to replace the then service pistol, the S&W M15 Combat Masterpiece. I was priveleged to read the test reports, and among a number of issues with the S&W M15 service revolver were that a large percentage of guns in inventory exhibited excessive headspace and barrel-to-cylinder gap, and many of these then developed bullet-in-bore malfunctions with the M41 130 grain RNFMJ bullets. These studies were also of interest to the US Army and Navy because they had large quantities of M19 and M15 revolvers for issue to aviators.

Among the interesting things studied were 130 grain RNFMJ bullets seated deep in the cartridge cases and larger powder charges for higher muzzle velocities, rechambering to 9x19 NATO caliber, and hotter ammunition in standard .38 Special format. The conclusions reached after all of these experiments were that they were unfeasible because of accellerated revolver wear and reduced service life. The subsequent Service Pistol trials of 1984-85 resulted in the selection of the Beretta 92SBF as the new service-wide pistol.

I guess what we can learn from these carefully documented studies is that hotter ammunition than a gun is designed for will result in more rapid wear and push toward unserviceability. The hotter the loads, the faster the wear. That is not to say that you can not ocassionally fire hot ammo, but only that there ultimately is a price to pay for it.