Traditional bullet jackets are made from an alloy called "gilding metal," which is a copper/ brass alloy made from 95/5 copper/zinc. The "bimetal bullets”, particularly associated with inexpensive steel-cased ammo, is ammo that uses a steel jacket rather than copper. The steel jacket may then be plated with copper, nickel, zinc or similar metals to provide corrosion resistance and somewhat increase lubricity. The plating on bimetal bullets is often quite thin, and bi-metal bullets with a steel jacket are known to be harder on barrel life in the long term. It's fine on most guns, just make sure to clean the barrel. Its fine in most cases (just make sure you properly clean the barrel) and if your barrel is chrome lined then you should not worry. I hope this helps!

William, bi-metal is a certain percentage mix of still and copper. It will attract a magnet and many ranges do not allow this type of bullets. The higher the steel percentage of steel, the harder the bullet jacket and more barrel wear. Cheers and stay safe!

WOLF's Bi-metal ammunition has a copper and steel mixed jacket instead of a jacket entirely made of copper. Unlike copper jacketed ammunition, Bi-metal ammunition will accelerate barrel wear. You will begin to see some barrel wear using the Bi-metal jacketed ammunition after about 5-6K rounds.