The ol' K-frame magnum forcing cone thing

[handyandy357]

Hi folks!
As a new owner of a 4" model 66 the stuff I've found about shooting 125 grain hot magnum rounds causing forcing cone and flame cutting issues has raised some concerns.

I don't want to open a can of worms, but I have some (probably silly) questions that I haven't been able to find the answers to.
I have a T/C Contender with a .357 magnum barrel in which I shoot the cheap .357 mag Winchester 110 gr JHP ammo from WalMart for plinking and targets. I've stored up several boxes of the stuff.

Would this load be OK for the 66 or does it fall into the same category as the 125 gr stuff that might cause problems? Should I stick to the 158 gr stuff? Granted, I'll never put the number of rounds through the 66 that law enforcement did and I'll probably shoot mostly .38 spls.

And just to be sure, the 125 gr .38+P is no problem right?

Thanks,
Andy

 

[shawn mccarver]

Hi folks!
As a new owner of a 4" model 66 the stuff I've found about shooting 125 grain hot magnum rounds causing forcing cone and flame cutting issues has raised some concerns.

I don't want to open a can of worms, but I have some (probably silly) questions that I haven't been able to find the answers to.
I have a T/C Contender with a .357 magnum barrel in which I shoot the cheap .357 mag Winchester 110 gr JHP ammo from WalMart for plinking and targets. I've stored up several boxes of the stuff.

Would this load be OK for the 66 or does it fall into the same category as the 125 gr stuff that might cause problems? Should I stick to the 158 gr stuff? Granted, I'll never put the number of rounds through the 66 that law enforcement did and I'll probably shoot mostly .38 spls.

And just to be sure, the 125 gr .38+P is no problem right?

Thanks,
Andy

It has to do with the short bullet in Magnum loads not sealing the barrel cylinder gap quite long enough. The lighter the bullet, the shorter it is, thus less "seal" time as it passes through.

Thus, I don't use anything lighter than 145 grain Silvertip and I prefer the Remington M2 load (158 grain JHP Magnum in my Magnum).

The problems with the 19/66 and other K frame Magnums did not really start until light bullets were used AND people started using nothing but Magnums with light bullets for everything, as opposed to just sighting in and occasional familiarization.

Occasional use of longer bullet Magnums (145 and 158 grain) will not, in my opinion, cause you any real issues.

 

[lhump1961]

As stated...158gr and good to go!

 

[handyandy357]

OK guys, I'll stick with 158's in .357 magnum for the 66 and leave the 110's to the T/C.

Thanks

 

[AR_Paratrooper]

Thanks for the info here. I just picked up a 65 and have been looking at a 66. I didn't really understand the bullet weight issue, but I do now. Thanks for the question Andy and Shawn for the answer.

 

[dynamike]

This may be off topic a bit, but does the same apply to a j frame magnum? I don't recall reading anything about cracked cones on j frames. I know some have the warning about bullet weight on the side of the barrel.

 

[handyandy357]

J's are fine.
The bottom OD of the forcing cone on a K frame magnum is trimmed off to allow the cylinder to open and close. The cracks appear in that thinned down area.
It's why L frames were invented I think.

 

[BillyMagg]

It has to do with the short bullet in Magnum loads not sealing the barrel cylinder gap quite long enough. The lighter the bullet, the shorter it is, thus less "seal" time as it passes through.

Thus, I don't use anything lighter than 145 grain Silvertip and I prefer the Remington M2 load (158 grain JHP Magnum in my Magnum).

The problems with the 19/66 and other K frame Magnums did not really start until light bullets were used AND people started using nothing but Magnums with light bullets for everything, as opposed to just sighting in and occasional familiarization.

Occasional use of longer bullet Magnums (145 and 158 grain) will not, in my opinion, cause you any real issues.

In my old 27-2 I shot nothing but 110 grain WW white box ammo, after 10 years or so and maybe a 1000 rds, I found significant flame cutting of the top strap, just made me sick, as I was attempting to baby my ole 27, now it just progresses to a point and stops, but it will definetly leave its mark? Billy Magg

 

[diamonback68]

The other problem besides the "seal" problem is the shorter bullets, being lighter accelerate faster than heavier bullets, and being shorter have a longer distance before meeting the forcing cone, this "jump" causes a "slamming" affect as it hit's the forcing cone. This causes greater pressures on the thinner area of the forcing cone plus the aforementioned plasma gases and flame cutting.