Multiple steel types are used in the manufacture of the nbsp ar 15 barrel.
Chrome moly vs stainless steel ar 15.
Chrome moly means chromium molybdenum alloy steel the usual material for gun barrels and other parts excepting things like aluminum ar recievers of course chrome lined means that the bore and chamber of a barrel probably made out of chrome moly alloy to start with has been plated with metallic chromium.
It has an advantage is it is less difficult to cut the rifling in the 4140 than harder 4150 which makes for slightly better accuracy in theory.
So which steel is the best ar 15 barrel material then.
The name given by the society of automotive engineers sae usually follows the pattern 4xxx.
Chromium molybdenum specifically means a family of steel alloys that when used for hand tools have a moderate amount of carbon often around 0 4 to 0 5 around 1 chromium around 0 15 to 0 20 molybdenum and a range of other alloying elements.
This is where the real differences between chrome moly cm and stainless barrels become apparent.
First let s have a discussion about the chemical elements of each material and how their properties effect barrel life accuracy and cost.
Regular 4140 moly is just a regular barrel steel it will last a long long time with the most often used twist rate on one turn in 9 inches.
Chrome moly or stainless steel.
Some other manufacturers prefer to chrome line the inside of their ar barrels and some do not.
When we start talking about stainless steel barrels everyone assumes we re talking about precision rifles and match grade barrels.
Some manufacturers prefer to use 4140 or 4150 steel while others prefer to use 416 ss or 416r steel for its properties.
Steel is alloyed with other metals like nickel and chrome as well as other non metals such as carbon sulfur and silicon.
