Corrosive loads and Forcing cone damage?


July 14, 2011, 09:00 PM
Ok i'd like to get opinions on what is going to take a toll on my firearms and what will not. I hear alot about "corrosion" and forcing cone damage from shooting certain loads over long periods of time. For example, my .357 magnum, i hear that some of the 125 grain loads are not good to shoot alot of. Why is this? What powders are safe to use that are not corrosive so i can load bulk 125 grain loads for both my rifle and pistol. Any info is appreciated.

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July 14, 2011, 09:23 PM
I believe that what you are referring to is "erosion" not corrosion. Corrosion would be a factor if the gun was never cleaned and allowed to rust, but particular types of ammunition can influence "erosion".

July 14, 2011, 11:42 PM
I hear alot about "corrosion"

Modern "powders" are not corrosive. Corrosion is "rust" when firearms aren't cleaned and lubricated properly and made worse by being in warm high humidity climates.

Steve C
July 15, 2011, 03:36 AM
125gr .357 mag can be an issue when using them in K frame .357 revolvers like the model 19 and 66. The problem is they can cause the forcing cone to crack in the area at the bottom of the barrel where it has been cut thinner to fit the K frame. This article explains it and has pictures:

Erosion is the wearing of the rifling or forcing cone (in revolvers) that is caused by the heat generated when shooting. Slow powders and/or heavy loads will usually accelerate erosion and shorten barrel life. Similar problem exist in rifles with high velocity, smaller caliber, cartridges that use lots of powder relative to caliber. How much or how fast the barrel erodes can be somewhat controlled by selection of load and powder.

As others have said, "corrosion" is oxidation or rusting of the metal.

July 15, 2011, 07:36 AM
Powders and primers sold commercially are no longer "corrosive".

Some surplus ammo is corrosive.

Erosion happens from the hot, high temperature gases produced when powder burns. Double based powders burn hotter than single based powders. It is hard on everything close to the chamber.

Top strap "cutting", or corrosion, in revolvers happens from the hot, high temperature, high velocity gasses escaping from the cylinder gap. Low bullet weight hot loads using a lot of powder are notorious for causing this. In other words, the hot 125 Gr loads in .357 blamed for top strap cutting on K frame revolvers.

July 15, 2011, 09:00 AM
Flame or Gas cutting is not common but happens. Large amounts of powder with light bullets seems to produce it more then heavy slow bullets. Erosion in the forcing cone does not seem to hurt accuracy. A S&W M29 with very severe erossion still shot Ok. Photo of Ruger 357 Maximum & a Dan Wesson model 40 (357 SuperMag)

July 15, 2011, 09:10 AM
Awsome info guys! I just wanted to clear that up and get a better understanding of it. Those pictures really helped as well!

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