K frame .357's warning from friend

[Ben Cartwright SASS]

I currently have 3 .357's, 2 N-frames and one K-frame. A friend invited me to go silouette shooting, he said to bring the N's not the K because feeding .357 through a K-frame .357 will eventually stress the frame and could lead it to fail.
I usually shoot .38's through the .357's (cheaper) and have heard this in the past from various sources.

What is the story on K frame .357's and shooting standard load .357 rounds? How many do you have to run through it before worrying?

 

[lagavulin62]

it's a very common question and the answer is as long as you stick to at least 158 gr bullets(357) you should not have a problem. any size is fine for 38 special.

for an approximate round count the spec guys will be along soon.

 

[Pisgah]

>What is the story on K frame .357's and shooting standard load .357 rounds? How many do you have to run through it before worrying?


I've never worried about it, and never will. Yes, excessive shooting of light (125 gr. and under) magum loads may cause problems, and will definitely acclerate routine wear; but all mechanical devices wear out eventually, and it takes 1000's of rounds for a K-frame to show even a little wear, much less wear out completely.

 

[fyimo]

The problem with shooting 125 grain 357 Magnum rounds in a K frame is well documented and it can lead to a cracked forcing cone and flame cutting on the top strap. I think it would take quite few rounds but can still can happen.

 

[Dale53]

The "K" frame .357 Magnum was actually a rather brilliant solution to a real problem for many LEO's. They are SO weighted down with belt equipment and the lighter, more compact "K" frame Smith worked very well. It was intended to be shot with .38's for practice and then carry full charge ammo for "real" use on the street. It worked very well for it's intended uses. It was developed at a time when the 158 gr bullet was the norm for both .38 Special and .357 Magnum.

It was a perfect example of "Carry a lot, and shoot a little" and did it's job well.

However, when high velocity lighter bullets became the "rage" then deficiencies started showing up and it was eventually dropped.

I had one and shot LOTS of 158 gr home cast bullet full charged ammo for several years and never had one bit of problem with wear OR failure. I eventually sold mine to buy a very nice 686 CS-1 (which I still have and enjoy).

Dale53

 

[roaddog28]

Here is a summary of a acticle on the effects of shooting full power 125 gr or lighter 357 magnums through a 357 magnum revolver. The subject of the K frame magnum and cracked forcing cones is because of the flat machine surface on the bottom of the revolvers forcing cone. But the affects of shooting large amounts of full power 125 gr or lighter is the same for any revolver.

The 357 125 gr "full house" is availiable from Federal, Winchester, Remington, Buffalo Bore and others. Basically, the 125 gr full house travels faster at 1500 fps to 1600 fps than a 158 gr round in a 4 inch barrel revolver. Back in the days when LE used a revolver this round was developed as a improvement to the 158 gr round. Experts in the industry claims this 125 gr round is the best manstropper still availiable. This includes all the rounds availiable for semi-autos. Whether this is true anymore is unclear. From my experience in my 357s the round has a lot of blast and recoil. I only have full size revolvers. Plus this round is much harder on a revolver than the heavier grain rounds. Any revolver that has seen a lot of this round can if not taken care of and cleaned on a regular basis wear the forcing cone out sooner. There are reports that shooting alot of the full power 125 magnums in even a heavier revolver has resulted in erosion of the forcing cone. One forum member I know wore a Ruger GP100 out in the barrel shooting a large amount of the full power magnums. There is also a member on this forum that reported wearing out barrels on their Ruger Security Sixes shooting large amounts of full power 125 magnums. So, it comes down to a descision by the individual.

Here is part of a post that explains the affects of the lighter grain full house 357s.
The lighter bullet causes a few things to happen.

1: It accelerates faster in the cylinder, striking the forcing cone MUCH harder than the 158gr bullet.
2: The shorter 125gr bullet leaves the case before a 158gr bullet, causing more unburned powder to fly forward and combust in the throat and barrel. This causes flamecutting on the topstrap and peening of the forcing cone. Again, very bad.
3: The recoil impulse of the 125gr loads are much sharper and severe than a comparable 158gr load, so it batters the gun HARD.
4: To be honest, the 125gr load is the most common out there, but it is not the best load. It is light and fast and while it expands violently, it tends to underpenetrate. The 158gr expands and has enough momentum to smash through and hit vitals.
Bottom line: A person can shoot 140 to 158 gr magnums through their K frame magnum. You want to stay in the velocity range of 1100 to 1300 fps. A person needs to clean the revolver after each range session especially in the forcing cone area. This means removing lead desposits. Lewis lead remover is good for this.
I shoot in all my 357 magnums 158 gr 357 magnum ammo. This includes my model 13, 19 and 66. I clean them after every session.
All of the above information I have researched and some of my statements are my own opinion. You can search this forum as well as others and come up with most of the information I have stated.
Regards,
Howard

 

[Bullseye Smith]

Here is what happens when you shoot hot loads:

 

[roaddog28]

Here is what happens when you shoot hot loads:

Good picture Bullseye. As one can see the flame cutting shows a lot of light grain full power 357 magnums put through the revolver. Flame cutting is like a blow torch cutting metal. Most the time flame cutting is self limiting. The erosion of the forcing cone can happen with any 357 magnum. Bullseye's picture is a K frame magnum. But this round is hard on any revolver.

Howard

 

[Maximumbob54]

The "No more 19 or 66 barrels" is the only reason mine only eat .38's. So the gun in Bullseye Smith's pic is like that until he can find what is becoming a scarce item. A Combat Magnum being reduced to paper weight status just isn't worth it to me. Sure, it might not happen... But...

 

[RychenCop]

i posted this S&W email reply to my K frame forcing cone question in another thread.
"As a rule any grain under 120 will corrode the barrel ( .357 ) ( .38 & .38+P ) are Ok"

 

[Gearhead Jim]

When S&W did the action job (nice!) on my 66-6, they included a note:

"Sir-
.38 special for practice
magnum loads for carry"

 

[dlay]

I called Smith and Wesson and asked this question, the tech told me that any American weight 357 SAMI spec loads are ok, not to worry about them, no matter what weight bullet. I have shot some hot reloads years ago, wont do that again, but wont worry about factory loads.

 

[Protocall_Design]

Some of the forcing cone erosion is due to ball powders going at high pressure and velocity. This acts like a sandblaster on the forcing cone. Those who reload can choose a flake powder to cut down on this erosion. Ball powder erosion happens on any barrel.

 

[358156hp]

I called Smith and Wesson and asked this question, the tech told me that any American weight 357 SAMI spec loads are ok, not to worry about them, no matter what weight bullet. I have shot some hot reloads years ago, wont do that again, but wont worry about factory loads.

This is because the 357 mag was castrated by SAAMI as the result of some gun manufacturers complaining about damaged guns because of the excessive pressures. As a result, the 357 Mag maximum pressure was lowered from 42,900 CUP to 35,000 CUP, and later to 35,000 PSI when piezoelectric transducers became commonly used for measuring chamber pressure. This is why the 357 data in the older reloading manuals is so hot. So some guns were reintroduced after being discontinued for long-term wear issues, and why we can now have 357 mag J Frames in both steel and lightweight alloys. Current 357 mag pressures are lower than the industry 38-44 pressures of the past, 42,000 CUP. The 9mm parabellum is in a similar situation.

 

[SeamasterSig]

The problem of cracked forcing cones is real, but it never reached epidemic levels even "back in the day" when the issue first became known and K-frames earned their "weak" reputation. The issue of K-frame durability did not surface until police departments switched to and later also began practicing with hot 125 grain carry loads – and the shooting public followed suit. Yet it can hardly be said that the magnum loads with heavier bullets that people preferred to feed their K-frames for the preceding 50 years were somehow anemic.

I have a four inch model 66-2 that I love and I think your friend's concern about your K-frame is much ado about nothing. If the K-frame design was the inherently flawed, the issue would have surfaced much earlier. As others have noted above, stay away from the ever-popular 125 grain flame throwing JHPs and stick with the 158 grain bullets the K (and J-frame) was designed around – or at least the standard wadcutter weight of 148 grains. Enjoy your K-frame for the brilliant compromise between carryability and shootability that it is. Love it, but don't necessarily baby it, for it can surely handle more magnum ammo than you can, provided you forgo those 125 grainers.

Oh, and don't forget to keep your forcing cone free of lead build-up and check your timing regularly – especially if you shoot a lot of magnums. I think that last point is especially important considering that the forcing cone is your K-frame's Achilles Heel.

 

[scooter123]

Guys, the problem isn't due specifically to lighter bullets, it's the increase in Kinetic Energy that a lighter bullet can produce. Some hard numbers.

First, a 158 grain bullet at 1200 fps., a reasonable result for a 4 inch barrel in 357 Magnum. (1/2 x (158/70000) x (1200^2))/32.2 = 504.7 ft.lbs. BTW, that 32.2 factor is the acceleration of gravity.

Next a 125 grain bullet at 1450 fps. (1/2 x (125/7000) x (1450^2))/32.2 = 583.0 ft.lbs.

What this means is that there is a 16% increase in the produced Energy and it is that increase that leads to a split forcing cone. Basically the K frames that featured a flat on the bottom surface by the forcing cone are somewhat marginal for full power 357 Magnums and when you increase the energy by just 16% you go over that critical "tipping point" that results in damage to the forcing cone.

 

[SeamasterSig]

Guys, the problem isn't due specifically to lighter bullets, it's the increase in Kinetic Energy that a lighter bullet can produce.

I'm going to have to disagree with you on that point. I think it is specifically due to the lighter bullets combined with a heavy charge of slow-burning powder. A 158 grain bullet moving at 1200 fps is certainly reasonable, but by no means extreme. It's possible to push that same bullet to speeds approaching 1500 fps, increasing the energy to around 800 foot-pounds without exceeding the pressure limits for 357 magnum.

Earlier magnum ammo was reputedly hot and heavy. Yet cracked forcing cones did not become a widespread problem until light, hot jacketed ammo became very popular in the late 70s/early 80s. S&W has been notably silent on this issue. How much revenue from the sale of L-frames do you think S&W would have forgone over the years had they simply warned everyone to stay away from 125 grain JHPs and shoot heavier lead bullets instead? There would have been a market for the beefier L-frame anyway, but S&W certainly made more money by letting everyone believe that they needed a new gun.

I have posted my thoughts on this before at length in posts #15, #22, and #29 of this thread concerning the strength of the model 686. Admittedly, I ramble a bit in those posts, but I think there are some good points in that discourse. However, for anyone who lacks the time or patience, the Cliff Notes version is simply to stay away from hot, light-for-caliber JHPs packed with slow-burning powder and check your timing regularly.

 

[BE Mike]

The "No more 19 or 66 barrels" is the only reason mine only eat .38's. So the gun in Bullseye Smith's pic is like that until he can find what is becoming a scarce item. A Combat Magnum being reduced to paper weight status just isn't worth it to me. Sure, it might not happen... But...

There are plenty of available custom barrels available for the model 66. If I had one crack, I'd just send it off for rebarreling by a custom shop.

 

[Invictus357]

I called Smith and Wesson and asked this question, the tech told me that any American weight 357 SAMI spec loads are ok, not to worry about them, no matter what weight bullet. I have shot some hot reloads years ago, wont do that again, but wont worry about factory loads.

Way to necro a 6 year old post

 

[SeamasterSig]

Way to necro a 6 year old post

It is no less timely than it was six years ago.

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