I know the general wisdom for K frames is to stay in 158 grain for .357's, but what about lighter .38 +P rounds, say the Speer Gold Dot 135 grain .38 +P? Will any .38 or .38 +P be fine in a K frame, or should you also stick to heavier .38 rounds?

In a .357 gun, you can shoot all the .38+P and never have to worry. I load almost all my .38 J-frames and K-frames with Speer Gold Dot 135 grain +Ps. Great defensive load.

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Dick

Shoot away!

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Isaiah 55:8-9
Phil. 4:13

The general rule concerning use of +P ammunition in the K frame is to only use +P ammo in a MODEL Stamped K frame. This will insure that the steels used will be of "modern" vintage and heat treated to "modern" specifications.

Prior to WWII there was a lot of variation in the quality of basic steel ingots and variation in heat treat methods and measuring techniques. WWII pretty well sorted out those issues and steels became a lot more consistent due to lessons learned during wartime production. There was also a lot of man hours put in by various manufacturers and armories in regards to heat treating, so that also improved a lot after WWII. However, post war there were material shortages that took some time to get sorted out, so using the model marking rule is a somewhat conservative approach that any S&W purchased is truly up to date in regards to materials and heat treating.

Now, in regards to the specifics of your question, I would recomend using the muzzle energy of any +P load under consideration as a guide. If it's less than 300 ft.lbs. from a 4 inch barrel any bullet weight will be safe in a modern K frame. From what I've seen looking around, the 38 +P commercial offerings generally run around 250 ft.lbs. which is low enough that it shouldn't be a concern. However, keep in mind this only applies to the steel framed revolvers and the aluminum framed model 12 is NOT +P capable.

Shoot it, shoot it, shoot it!

The only K frame I would not shoot +P in is the Model 12.

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Centennial Every Day

There is also +P+ in .38 Special. Originally, it was loaded to an individual police agency's specifications, and was intended to provide low-end .357 Magnum ballistics to departments that wished to avoid use of the .357 Magnum cartridge for political or public relations purposes. Many such departments ordered it and intended it to be fired in .357 Magnum revolvers.

There have never been industry standards for what constitutes +P+ pressures, unlike standards set for +P and standard velocity/pressure .38 Special ammunition. Pressures of any individual lot are what the manufacturer decided they would be, maybe in consultation with it's contracted purchasing agency.

I wouldn't shoot +P+ in any J or K frame .38 Special revolver.

I was wondering if anyone else remembered +P+ ammo in .38 Special. I have several boxes left over from the '80's.

I have a bunch of the Federal +P+ and it's super accurate ammo.

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Centennial Every Day