Strange Milling on a Nickel 10-6..

[RevolverJockey]

Picked up a $250 private sale M10-6 with 4" barrel and Nickel finish. Someone had installed a target hammer, trigger and grip but the price was right and the finish is very nice. I was looking it over and notice a strange milling on the front of the cylinder. There are two cuts on visible from each side and appear to meet at an angle right under the forcing cone. This has the same nickel finish as the rest of the gun appears to be done well if that makes sense. Has anyone seen this before or have any idea what it might be? I can only narrow down manufacture date to 61-77 as I have not really researched it much SN is D927105. Thanks,
Lee

 

[john traveler]

Model 10-6? Was that the first M&P model in .357 Magnum chambering? The predecessor of the M13?

It appears that your gun has the engineering modification that moved the gas ring from the cylinder to the crane. The modification was in answer to reported seizing up of cylinder rotation from rapid and extended firing of magnum ammunition. I believe that the cuts were put there to increase heat dissipation and reduce expansion of the gas ring and cause cylinder binding.

 

[RevolverJockey]

Model 10-6? Was that the first M&P model in .357 Magnum chambering? The predecessor of the M13?

It appears that your gun has the engineering modification that moved the gas ring from the cylinder to the crane. The modification was in answer to reported seizing up of cylinder rotation from rapid and extended firing of magnum ammunition. I believe that the cuts were put there to increase heat dissipation and reduce expansion of the gas ring and cause cylinder binding.

You could be on the right track. In Roy's book, he provided a table giving Model 10 engineering revisions -1 through -6 and none list this change. Under -6 the only thing listed is "same as 10-5 except heavy barrel". I can't imagine if someone sent this gun back for the change, that the factory would have refinished this part, perhaps replaced it but I would expect the factory would have updated the gun to a -8 which I believe was the gas ring relocation for a heavy barreled 10. It is a mystery.
Lee

 

[john traveler]

So, is your revolver chambered in .38 Spl or .357 Magnum?

 

[Texas Star]

Lee-

The changes may have been across the K-frame Magnum and .38 line at that time, after Massad Ayoob blew the literary whistle on K-mags seizing up. (Mas ,if you see this, nice work!)

However,some early .357 guns made for the Okla. Hwy. Patrol were marked 10-6. I don't think they were commercially released, except perhaps as police surplus. The M-13 was the commercial version, also furnished to most law enforcement orders after those first Oklahoma guns.

 

[BUFF]

Actually, the .357 Magnum Model 10-6's were manufactured for the New York State Police. The 10-6 was usually made in .38 Special, in blue or nickel finish. The Magnum variant became the Model 13 in 1974.

The Oklahoma Highway Patrol gun was stainless steel and first marked as Model 64-1, which was normally chambered in .38 Special. It was soon marked as the Model 65 when in .357.

 

[RevolverJockey]

This one is chambered in 38 spl.
Lee

 

[RevolverJockey]

Still solution on this milling anyone? Can anyone narrow it down when it was made for a possible call to Smith? SN is D927105. Thanks,
Lee

 

[Dragon88]

You could be on the right track. In Roy's book, he provided a table giving Model 10 engineering revisions -1 through -6 and none list this change. Under -6 the only thing listed is "same as 10-5 except heavy barrel". I can't imagine if someone sent this gun back for the change, that the factory would have refinished this part, perhaps replaced it but I would expect the factory would have updated the gun to a -8 which I believe was the gas ring relocation for a heavy barreled 10. It is a mystery.
Lee

No mystery here. My nickel 10-6 has the same cuts.

 

[RevolverJockey]

No mystery here. My nickel 10-6 has the same cuts.

I don't know if you understood the question. It is not a mystery that they are there - I am looking right at them. I was more inquiring as to WHY they are there.
Lee

 

[Alk8944]

The cuts are in the gas ring that was integral to the yoke. They are intended to deflect gasses from the yoke/cylinder gap.

In about 1975, apparently as a cost cutting step, S&W moved the gas ring from the cylinder and replaced it with a solid collar on the yoke that was supposed to do the same thing. The slots were cut as gas deflectors but didn't function as intended. In 1977 the gas rings for all revolvers were moved from the yoke back to the old style in the cylinder. The only exception seems to be the .38-.357 J-Frame guns where the gas ring is still on the yoke.

The reason for returning the gas ring to the cylinder to the cylinder is fouling from firing would build up between the yoke and cylinder and result in binding of the cylinder after firing many fewer rounds than with the old style.

All revolvers will bind from fouling in this area. How many rounds can be fired depends on ammunition being used and clearance between the cylinder and yoke in the cylinder axis bore. This is why it is important to remove the cylinder frequently and clean the yoke and lubricate it.