K frame question

[BunkTheory]

Once read an article from the 1990s about a group of guys who were hot rodding GP 100s, using heavily pointed bullets and loads aproaching 60,000 cup or PSI on their testing gear. They said the guns were fine as the pointed bullet reduced stress when it entered the forcing cone.

Also read hints and suggestions here and there that the use of wadcutters was a bad idea as the flat front increased impact stress on the forcing cone slightly. Never had any indication of by how much the stress was increased.

So we all know the super light weight bullets and magnum loads, and shooting lead and jacketed bullets without proper cleaning in between the two types of bullet helped create the forcing cone crack issue.

Im just curious as to how much the cracking was impacted by officers using their duty guns for Bulls Eye shooting and PPC shooting with wadcutter loads... some guys claimed 10,000 rounds minimum a year for shooting and practice for contests so im just thinking on the correlation.

[rintinglen]

Very few officers used their duty revolvers for that level of use. If you were into PPC, at least by the late 70's, you shot a gun specifically tuned and prepped for PPC. The duty gun stayed in the locker when not in service, save for the occasional "duty gun" match or qualification.

I sold my Davis PPC gun in 1984 with 34,000 rounds through it--by me, how many the guy I bought it from had previously sent down range is a question I can't answer. 2.7 grains of bullseye under a Remington or Speer HBWC, or 3.0 grains under a cast 148 button nose wad cutter simply don't generate that much pressure, and consequently, not that hard of an impact. It was still serviceable, and smooth, albeit worn.

[Boolit_Head]

Back in the 80's I was one of those running my duty gun in early ppc competition. Some weeks my 686 was fed around 800 rounds a week. They were everything from wad cutters to jhp depending on what I had or cast then it would get cleaned up and loaded with silvertips for duty use. I stayed with published loads at the time and never had any issues. That gun still sits in my safe as a prized possession with no issues. If you go back to my load books I used then the loads of today seem lighter but I suspect a lot of the issue was running to hot and to heavy. The K frame is good but within it's limits. Quality wise I also would not compare a older Smith K frame to a Ruger GP100.

[Outpost75]

K frame will not stand up to high volume use of plus-P or .357 loads. Customs and Border Patrol tests of 1980s made this very clear. If you want to PM me with an email address which I can receive 20MB of .pdf attachments I can send to you.

Stick to standard-pressure .38 Special if you want the gun to last.

[TNsailorman]

I have seen a cracked forcing cone and the guy was pushing the limits with 125 grain jacketed bullets, plus P+. He admitted himself that it was a stupid thing to be shooting +P loads and the 125's for everyday use. I will not now or ever push a steady diet of +P loads through my Model 13. I carry +P for defense but that is all, they will never be a day to day load for me at the range. It is other peoples revolvers and they can do as they please, but not me. james

[Outpost75]

Read Mike Wood's article on Revolver Guy about barrel cracking on K-frame S&W.
Very through and well researched.

[tazman]

I had a model 19 forcing cone crack on me. Until the edges bent far enough to bind the cylinder, it didn't pose a problem or any accuracy issues.
I relegated it to 38 special wadcutter use until somebody made me a stupid high offer for it due to it's accuracy.
That would have been back in the early eighties and as far as I know, the man still uses it for wadcutter shooting. He knew the cone was cracked when he bought it but didn't care.

[RJM52]

I know one guy who cracked the forcing cone on a 60s vintage Model 15 with 110 grain Sierra JHC bullets and I believe SR-4756 powder that got the load into the 1200s...

My only long term experience with a K was a 1970 vintage 4" Model 19-3. Had a documented 10k rounds through it 90+% of which were the 158 grain Lyman/Thompson gas check bullet that was going 1200 fps. It went back to the factory for a tune up and was nickled. Another 10K went through the gun before it was sold in 1980. In that 20K rounds only 6 rounds of .38 Special ever went through the gun. I only had four revolvers and one 1911 at that point so it got shot a lot.

Shot one PPC match with that gun in 1977, won my class, found it boring, found IPSC and shot it till 1995...

Bob

[FergusonTO35]

K frame will not stand up to high volume use of plus-P or .357 loads. Customs and Border Patrol tests of 1980s made this very clear. If you want to PM me with an email address which I can receive 20MB of .pdf attachments I can send to you.

Stick to standard-pressure .38 Special if you want the gun to last.

Agree 100%. If you can't get the job done with a decent standard pressure load, you probably need to move up to a bona fide .357 revolver. My 10-5 loves 3.4 grains Bullseye under the Lee 358-158-RF. Accurate, easy to shoot, and smacks targets with authority. If I need something more than that I'm grabbing a rifle!

[Boolit_Head]

A lot of the +P loads were in the 357 range. I had some heavy 296 loads from that era for my 357 that just hurt to shoot.

[carelesslove]

carelesslove, here !

"OLD" gun sages (and I am 68) have always seems to "have it in" for the Model 19 - as it seems to have been the "original" target of the cracked forcing cone phenomena.

There might be a good reason for this. If we were look very closely at an older vintage Model 19, and move the cylinder to the open position, we could all observe the small, almost imperceptible flat spot at the bottom of the barrel, where the cylinder / gas ring "almost" comes into contact with the barrel.

This might hold the answer and pinpoint the weakest link in the K Frame design - when fired with loads at higher pressures.

This small flat spot visibly reduces the distance that escaping powder has to travel, before it dissipates its energy. If we see and understand how forcing cones erode - an inside-to-outside radial pattern - it might be easier to understand why the Model 19 barrel cracks at the 6:00 position.


S&W engineers of the early 1950's probably expended a lot of effort in changing the barrel / cylinder / frame material to a chrome / moly alloy to make it heat "treatable", and therefore - much stronger. More than likely, if our Model 19s didn't erode their forcing cones, we might never think there was a problem shooting "modern" .357 Magnum ammo in them. Even with the "flat spot", the Model 19 forcing cone area is plenty strong, but it is probably not strong enough, when the radial wear cuts across the flat spot.

When this occurs, the stress on the barrel cross-section goes "sky high" and it invariably cracks.

Let's make a clear delineation here. You really don't see a lot of N Frame barrel / forcing cone cracks - do you? If you look at the back of the barrel on an N Frame, it has no flat spot. Approximately 50 years ago, I only had one gun - a 4" Model 28-2. I learned to shoot, cast bullets and reload with this gun. I was a greasemonkey at a gas station and had a seemingly limitless supply of (good) wheelweights. I tried to shoot this old 28 to death and almost succeeded. I managed to burn off the back of the barrel and completely erode anything that resembled a forcing cone. It looked like 80 grit sandpaper. Back then, S&W had a good laugh at me - and replaced the barrel for free!

But, there were no cracks..........

I know and understand the advent of the "hotter burning" ball powders and the quest for lighter bullets at higher velocities - I tried it myself. But, if you fire enough "magnum-level" rounds with virtually any powder / bullet combination, you will erode your revolver's forcing cone and the back of the barrel. The Model 19 just has its' own, unique limitation.

Standard velocity / pressure cartridges, like the .38 Special - operating at ~15,000 psi - just don't "burn up" their barrels. Raise that pressure to 35,000 psi - with the same geometry and the forcing cone game changes. Admittedly, the use of chrome-moly steel helps, but time & pressure will take its' toll.

I still own, shoot, and enjoy my 19-2 and a slightly newer 66-1. I try to take care of them and keep the velocity (1000 ft/sec) & pressure (~20,000 psi) down, while still shooting them a good bit. I have not seen any measurable erosion at ~1000 ft-sec, but every now and then I do step it up a little.

As I age (at an increasing rate) I am getting a little more recoil-sensitive and keeping velocities below sonic levels might prolong my failing sense of hearing, but when I experience "the need for speed", I go to the N Frames and save the K Frames for yet another day of lower pressure shooting.

The K Frame .357's are great revolvers - just try to resist pushing them past their limitations.

I hope my opinions & rambling sense to all of you.

Tom "carelesslove" Love

[TNsailorman]

careless, I enjoyed your piece and you pointed out something that I should have but left out because I have been told I did not know what I was talking about when I pointed to that flat spot on the bottom of the forcing cone. I am convinced that it is the weak spot in the K frames. But ammunition can play apart also. I bought a box of Remington 125 grain .357 a few years ago and it was really hot. There was a noticeable difference between the ammo in that box and other .357 I had tried out in in new Model 13 before. There was a very bright flash and more noticeable recoil from the ammo in that box. When I got finished shooting the box up and started to clean the revolver, I found the ammo in that box had cut a noticeable "flame cut" in the top strap. Remington must have used a very fast and hot burning powder in that loading. I never bought any more of that Remington offering. James

[brassrat]

I had some of that Rem. It was 125 gr SP and lots of kick. I bet there are 6 or 12 kicking around in multi load boxes I put together

[BunkTheory]

Read Mike Wood's article on Revolver Guy about barrel cracking on K-frame S&W.
Very through and well researched.

I dont want to hurt your feelings but i saw that website last night, and that website left me with some very unpleasant feelings. I havent seen that level of elitist attitude outside of video game/computer forums in quite some time.
I really appreciated reading that i was little more then an inbred child molesting, wife beating toothless hillbilly with webbed toes suckign on my thumb if i had a gun that wasnt made by kimber, colt, smith wesson, ruger, korth, or didnt have a specific make and model of holster, or didnt use a specific brand or grain weight of ammunition in my fire arm.

[M-Tecs]

Read Mike Wood's article on Revolver Guy about barrel cracking on K-frame S&W.
Very through and well researched.

This one is excellent also https://revolverguy.com/the-smith-wesson-l-frame-story/

[M-Tecs]

I dont want to hurt your feelings but i saw that website last night, and that website left me with some very unpleasant feelings. I havent seen that level of elitist attitude outside of video game/computer forums in quite some time.
I really appreciated reading that i was little more then an inbred child molesting, wife beating toothless hillbilly with webbed toes suckign on my thumb if i had a gun that wasnt made by kimber, colt, smith wesson, ruger, korth, or didnt have a specific make and model of holster, or didnt use a specific brand or grain weight of ammunition in my fire arm.

Which article are you referring too?

[BunkTheory]

Its just that with the 38 +p+ Treasury Load still being available, And a new super vel out on the market pushing a 90 grain hollow point to about 1300 fps in a 4 or 6 inch barrel, I really got to thinking as 110 and 125 are considered the minimum/"ideal" for self defense by the gun rags and gun websites.

[BunkTheory]

I read the whole website last night, the curse of insomnia. There are some rants about "that not so smart guy who just bought his first gun" that include alot of elistist insults to those who dont have a 300$ custom holster, or a kimber, sw, colt, ruger, korth revolver.

[tazman]

Its just that with the 38 +p+ Treasury Load still being available, And a new super vel out on the market pushing a 90 grain hollow point to about 1300 fps in a 4 or 6 inch barrel, I really got to thinking as 110 and 125 are considered the minimum/"ideal" for self defense by the gun rags and gun websites.

At one point, the 357 with a 125 grain hollow point was considered the best one shot man stopper available. This was before the development of our current hollow points in 9mm, 40S&W, 45ACP, etc.
I suspect some of those writers have never tested any of the new stuff with an open mind.
The fun part is, all the old cartridges that were successful all those years ago, are still quite capable of doing the same job now. They didn't suddenly lose the ability to cause bad guys to stop doing bad things. Other stuff just got better than it had been previously.
A deadly weapon is still deadly no matter how old the concept is.
As to the FBI load still being available, all those old revolvers didn't just vanish from the earth. They still work and still need fed a good load that does the job.

[Outpost75]

I dont want to hurt your feelings but i saw that website last night, and that website left me with some very unpleasant feelings. I havent seen that level of elitist attitude outside of video game/computer forums in quite some time.
I really appreciated reading that i was little more then an inbred child molesting, wife beating toothless hillbilly with webbed toes suckign on my thumb if i had a gun that wasnt made by kimber, colt, smith wesson, ruger, korth, or didnt have a specific make and model of holster, or didnt use a specific brand or grain weight of ammunition in my fire arm.

No hurt feelings here. I have no interest at all in reading about new products and models. I am a dinosaur for whom an old gun that works is worth more than a new one that doesn't. Mike has some good technical and historical articles and those are the ones I read.

I'm not into $300 holsters or $6000 revolvers either. I own five shooter - grade Colt New Service revolvers and a couple Gen1 Colt SAs and I didn't spend $1000 for any of them.

[Mk42gunner]

There is a lot of difference in gun wear and tear between a lead wad cutter pushed by light charges of Bullseye, 231 or Red Dot and a jacketed projectile pushed by a near capacity load of slow burning ball powder at two to three times the pressure.

Also, if you get any ideas of trying those 60,000 psi loads; let me know so I can make sure I am no where near. I like the GP-100 as much as the next guy, but I am not going to load it to bolt action rifle pressures.

Robert

[Walks]

In 1977 I bought a Model 19 from a retired LAPD officer. He had subscribed to the then recent theory of practice with what You carry. Even though LAPD was still carrying the old .38Spl lead RN, he like others would practice with what they carried; .357Mag - 125gr SUPER-VEL HP's.
A violation of then Chief Ed Davis' policy of the old Lead RN. By the time I got My hands on this revolver it was in bad shape.
The forcing cone split on the first cylinder full of the "Skeeter load". It was sent off to S&W for repair. But the die was cast and I sold it off a few years later to finance Cowboy Shooting.

I remember the Newhall Shootout. The entire CA LE community was in an uproar, it was on every TV station and in all newspapers. the whole state talked of nothing else for weeks. A Very Sad Time.

[Wayne Dobbs]

Read Mike Wood's article on Revolver Guy about barrel cracking on K-frame S&W.
Very through and well researched.

I looked through several pages on that site and can't find the article you referenced. Can you help with a link to it, please?

[curioushooter]

When this occurs, the stress on the barrel cross-section goes "sky high" and it invariably cracks.

Regarding this, the entire circumferential barrel extension thickness of a J-mag frame 357 magnum is considerably thinner than the 6 o'clock position on a K-frame. Conclusion: even at its weakest point the K-frame is stronger than a J-mag frame. Yet we never hear of anybody cracking their J-mag frames. Why? Because J-mag frames were introduced after 1995, when SAMMI reduced the power level of the 357 and load books followed. At least that is my thinking. That and they are so light that shooting punishing loads will lead almost anyone to demur after a couple shots, replacing with some garden variety 38+Ps which work great in these.

Basically, be reasonable: do not shoot super high velocity bullets in K-frames, do not shoot really short bullets in K-frames, do not use very slow ball powders (296) or use them sparingly if you must. And none of this is necessary to thoroughly enjoy one, or use it effectively for what it was meant to do. 140-170 grain bullets, both cast and jacketed, work best and do the best work. Medium to medium slow powders work best for full mid to powerful loads...like Unique, Herco, BlueDot, 2400. I've done a lot of testing using powders slower and denser than 2400 (296, and 300MP) and the velocity gains are marginal out of a 4" revolver (these powders, however, are superlative in 357 rifles). Accuracy is never better. Unique or something like Universal are great all-purpose powders, and if you want some fast powder for target shooting/plinking then Bullseye or Tightgroup is nice.

I really like 5-6max grains of Unique, or 9-10max grains of Blue Dot with the 358429 (170 grain SWC) in 357 cases crimped in the groove (not crimped over the driving band as you must do in a N-frame) for the model 19, and I like to stay on the low end of those charge weights.

If you need more power than this, going faster wont help you much. Yes, you can get this bullet to go faster with 2400 or even slower powders. But why? It will not substantially increase terminal effectiveness and will probably diminish your practical accuracy, increase noise, recoil, powder consumption, wear, etc...

If you want more terminal effectiveness then get a bigger bore. For example...7.5 grains of Unique with the 429421 or similar (255-260 grain SWC)...in 44 special case will go 900+ FPS...the same velocity territory as the 357 Medium loads...but it's hurling a bullet that has 31% more frontal and is 34% heavier. Basically a third more terminal effectiveness at a minimum. And it's doing this at 38+P pressures (<22k PSI), so soft alloy are great, no copper diapers needed, and the cases last.

Using something like blue dot or 2400 in the larger bore size will do more with less, too. Some really top end 357 loads (which have no business in a K-frame or anything smaller) use 15.5 grains of 2400 or to push a 158 at 1400 FPS or so. 16.5 grains of the same powder, only a grain more, will propel a 260 grain SWC in 44 Special to 1250 FPS with about the same barrel length. I assure you, 150 FPS (an 11% increase in velocity), doesn't compensate for the over one third reduction in mass and diameter of the bigger bore. Even the most potent 357 loads can't match 44 SPL+P.

[curioushooter]

This is the link you are looking for: The Smith and Wesson L-Frame story (https://revolverguy.com/the-smith-wesson-l-frame-story/)

[Speedo66]

Regarding this, the entire circumferential barrel extension thickness of a J-mag frame 357 magnum is considerably thinner than the 6 o'clock position on a K-frame. Conclusion: even at its weakest point the K-frame is stronger than a J-mag frame.

The change in the circumference of the barrel, the K frame forcing cone flat spot, creates a "stress riser" or stress concentration area that is more prone to failure.

From Wiki: "A stress concentration is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress."

It's the shape, being out of round, rather than the thickness, that causes problems.

[MT Gianni]

One of Veral Smiths reasons for developing the RF style bullet was its aid in entering the forcing cone. It seems crazy but a little slop in the cylinder alignment allows better bullet fit that a tight one with misalignment.

The only light bullets my K frames get are at very low pressure.

[jonp]

This one is excellent also https://revolverguy.com/the-smith-wesson-l-frame-story/

Lot's of great information and history on that site. Seems a little high brow at times, though

[curioushooter]

From Wiki: "A stress concentration is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress."

It's the shape, being out of round, rather than the thickness, that causes problems.

I have doubt about this matter applying dramatically in this situation.

Another thing to consider is that the out-of-roundness is on the OUTSIDE of the barrel extension. If it were on the inside this would be a valid consideration I think. But as it is the inner part of the barrel is suffering the erosion and at the same rate all around its inner circumference. That is until it eroded close enough to the 6 o'clock position to start causing problems. But that degree of erosion would have long eaten though the thinner extension of the J-mag. Please, by all means examine a J-mag for yourself. The extension is shockingly thin. And if that is enough to contain 35kPSI 357 loads for whatever durability standard is set, then the K-frame is capable of that, or more. Modern K-frames have the same sleeved barrel as the J-mags (like a 60-18), with no relief cut made. I have not measured them but they are visibly thicker than a J-mag. The L-frame by comparison is just much more massive, as is the cylinder and the window. In fact, a L-frame is so large that it can be chambered in 7-round cylinders.

[Cosmic_Charlie]

I would never abuse my prized K38 with hot loads. I have a 687 and 27 for that and those see mostly medium loads with an emphasis on accuracy. Shooting mostly cast has steered me into more reasonable loadings. My alloy rarely exceeds 12 bhn in revovers.