Use of Magnum Loads in S&W Model 19 and Other K-Frame Magnums


by Butch Kent

Photography by Butch Kent

April 18th, 2006




To say the least, I am very fond of my Smith & Wesson Model 19 and am interested in prolonging its life a much as possible while still being able to use it as intended. So it was with some concern that I read reports that others had experienced a terrible disaster with their Model 19s: a cracked barrel throat. I had heard such stories in the past, but there were never any basis for them, just rumor. I needed to find out for myself from people who had the facts.

Over the past several months I have been in pursuit of hard facts that I hoped would put to an end, at least for me, the question of whether or not a full time diet of magnum loads would lead to premature failure of the K-Frame magnum revolvers. I have learned quite a lot and have had the good fortune to have had input from numerous sources including police officers, gunsmiths, shooting sports professionals, sportsmen, and hunters.  The results of this review are discussed in the following paragraphs.

Was I convinced that the claims of failures were Old Wives Tales? No.

Was I convinced that one should sparingly use magnum loads in the K-Frame? No…and Yes.

Will I change the way I use my Model 19? … No.

But… you should read the rest of the article and judge for yourself.

When the K-Frame magnum was developed it was intended to provide a lighter weight revolver for the .357 magnum cartridge. As such, it is somewhat of a compromise between the N-Frame revolver, the Model 27 and earlier .38 Special revolvers. In the beginning, most ammunition was lead 158-grain high-velocity as offered by most manufacturers. There is a good deal of information that points to the almost indefinite life of the revolver with reasonable care and a diet of 158-grain lead bullet magnum ammunition.

As gun enthusiast know, well enough is never left alone, and the inevitable urge for more power, higher velocity, and explosive terminal ballistics resulted in development of a number of jacketed bullets from 110 to 160 grains. These jacketed bullets could be driven to higher and higher velocities. Based on the “numbers”, they far out-performed their swaged or cast counterparts. Thus, the first magnum cartridge evolved rapidly. When introduced, the K-frame revolvers, due to their many desirable characteristics, became one of the most popular handguns on the market and sales far exceeded Smith and Wesson’s expectations.

As a young handgunner, my own load development efforts pushed the limits of the K-Frame capabilities. Without sophisticated monitoring equipment, I carefully approached each load increasing powder charges in small (0.1 grain) increments. Cautiously changing primers and even cases to detect any indications of excessive pressure. Primers were my key pressure indicator. As pressure increased the primer would begin to flatten out around the primer pocket and then start to flow back into the firing pin hole. Minute changes in powder charge could be seen to significantly increase chamber pressure, sometimes almost exponentially. On a rare occasion, a minor load change would result in cases sticking in the chamber. THAT’S DANGEROUS! S&Ws have great chambers and are not prone to resisting case removal. When a cartridge case sticks, it is a sign of excessive pressure and significant backing away should begin immediately. There are those who do not heed the signs and end up with seriously damaged firearms and possibly injuries.

Back to the question at hand: what should you shoot in your model 19? From my discussions, review, and the first hand accounts of many experts in the firearms industry, it is clear that in the design of the K-Frame revolver some compromises were made. These changes were made to create an easy to carry, powerful, accurate, and absolutely most beautiful handgun ever made. The changes also may have introduced some generic weaknesses. Most firearms have some generic design weaknesses. One of the weaknesses in the K-Frame is in the cut on the bottom of the barrel throat, in the forcing cone area, to accommodate the cylinder swing. In the attached photo you can see the flat region on the bottom of the barrel throat.

I’ve been told that when the Model 19-5 was issued, the production process changed related to the barrel installation in the frame. Barrels were compression, “crush-fit”, into the frame. Compression force could introduce stress and potential latent flaws in the barrel throat.

Cylinders long enough to accommodate full charge 158 grain bullets provide a great deal of free space when shorter bullets are used. A very popular loading for the .357 magnum was for the 125 grain jacketed bullet. In the early days, this was a great combination with high velocities and excellent terminal performance. Today’s bullet designs offer equal or better performance from heavier weight bullets and over a broader range of velocities.  The bearing surface length of the 125 grain bullet is shorter than the bearing surface of the 158 grain bullet. This difference means that as the 125 grain bullet leaves the case there is a gap between the leading edge of the bullet sealing surface and the cylinder throat. As the short bullet makes this jump, combustion gases and powder are permitted to blow past the bullet and prematurely escape into the barrel. The 158 grain bullet essentially seals off the cylinder as it leaves the case and enters the cylinder throat. More complete combustion of the powder is accomplished. Temperatures of the gas as it enters the barrel are lower and the combustion environment in the barrel is not oxygen rich as is the case for the prematurely escaping combustion gas.  Checking the dimensions of my 19-3 confirms that for the 158 grain HP bullet, the leading edge of the bullet is engaging the lands as the base of the bullet has just left the case mouth and is flush with the cylinder throat. For the lighter HP bullets of 115 to 125 grains, there is a gap of approximately 0.15 to 0.12 inch, respectively.

The problem with the gap of the shorter bullet is that it permits excessive hot burning gases to escape past the bullet into barrel throat. This superheats the surface of the barrel throat with the hot gas plasma. Still unburned powder blasts away at the barrel throat surfaces and the repeated impact of the high velocity bullets on the lower surface of the throat region result in erosion of the throat in this area. One might question why the impact and erosion is predominantly at the six o’clock position. Recoil. Longer bullets are guided by the cylinder throat and thus are not impacting the lower barrel throat as with shorter bullets. The shorter bullets have a longer “jump” from the case mouth to the barrel lands and thus pick up more velocity prior to engaging the rifling. This causes a greater impact force on the rifling contact area. Another detrimental effect is the flame cutting of the frame as these super hot gases escape from the cylinder-barrel gap. This problem would be present for short bullets in all models of firearms.

Based upon reports of those who have seen examples of throat cracks, several characteristics appear common. First, erosion at the six o’clock position in the throat is almost always present. Most describe this as “peening”. Second, the weapons have generally not been thoroughly cleaned after use. Deposit of lead and bullet fouling are present in the throat erosion region. These deposits can create conditions for chemical stress corrosion and initiation of microscopic cracks in the steel. Third, most of the weapons have other signs of excessive use and wear, possibly from overly hot loads. Very small to large cracks can form at this particular point, the six o’clock position, in the barrel throat. The impact force of the bullet on the rifling would increase the probability of a problem in this region.

Actual reported data collected during this review is summarized in the table below.

Model Number of Guns Observed Crack Y/N 158 grain Rounds Fired 125 grain Rounds Fired
19-5 3 Y 100s 1000s
19-7 3 Y 1,500-2,500 100-500
19-4 2 Y 2,500-5,000 1000
19-4 1 Y 5,000-10,000 (lead only) 0
19-4 2 N 5,000+ <500-1,000
19-3 1 Y ? 2,500
19-? 2 Y <500 150

It should be noted that a lot of weapons never see very heavy use. Initially, I would put 50 to 100 rounds per week through mine. This was during the period of load and skill development. After that, I probably only shot 250 to 300 rounds per year for the next 3 to 4 years. Once I had acquired several additional firearms to occupy my mind and time, my 19 became more of a hunting tool. Currently, I probably fire about 50 to 100 rounds per year. I conservatively estimate that my Model 19 has seen a total of 3000 to 4000 rounds. Today it is as tight and bright as it was the day it was unwrapped.

There are some other interesting tidbits of information gathered during this review. This phenomena is not limited to Model 19 revolvers, although S&W stainless medium frame models may be more resistant to crack initiation. On rare occasion, cracks have been reported with fewer than 150 rounds of the 125 grain magnum loads fired. A few reports of cracks have been made with only 158 grain loads used. One report was received of a Colt Python that cracked with the first box of 158 grain magnum shells. Also, I have even heard of an example where a new unfired revolver was purchased with a crack in the barrel from manufacturing. Even the best quality control is not perfect.

Notwithstanding my own observations, anecdotal data indicates that this crack failure occurs only rarely. Most people will never see such cracks in a lifetime of shooting. That’s why there is talk about the cracking phenomena without much first hand information. Some shooters fire many thousands of rounds per year. While they may eventually wear their guns out to the point of requiring parts replacement, they may never see the cracking. This has been the case with many of the people contacted during this review. Others significantly reduce the life of their weapons by what the feed it and how they care for it. Occasionally a defect will show up and prematurely fail the weapon.

What’s the bottom line? Smith and Wesson stands behind their products and when a rare failure occurs, they make it right. That doesn’t mean that one should stretch the limits of their weapons and ask them to do what they were not intended to do.

My Model 19-3 has been a great weapon and hunting partner for over 30 years. Maybe the production processes of the earlier models like mine give them some added resistance to the cracking issue. I will continue to shoot reasonable magnum loads in it with the full belief and confidence that it will outlast me. I take care of my Model 19 as one should for any good weapon.

I hope this discussion will help put this issue in perspective. Also by providing some factual information, though limited in numbers of examples, we may provide some insight into the causes of such failures. Finally, understanding the strengths and limitations of the very best magnum revolver, the Smith and Wesson Model 19, will enhance all of our shooting enjoyment and help preserve examples of this fine firearm for generations to come.

Butch Kent


Got something to say about this article? Want to agree (or disagree) with it? Click the following link to go to the GUNBlast Feedback Page.

Click pictures for a larger version.


Fig.1: Author's Model 19-3.





Fig. 2: Model 19 – Note flat area on bottom of barrel throat.





 Fig. 3: Note thin area and flat on barrel throat. Some guns are reported to be thinner than others in this area.