4140 Steel with Melonite QPQ Finish.

sorry I could not find where they listed the barrel as either 4140 or 4150 so I suggest that you contact Savage and ask them US: (413) 568-7001 or (800) 370-0708

William, Michael W doesn't know what he is talking about. He many times post incorrect answers on things he does not know.

It's 4140. 4150 holds up to 100- degrees higher temp than 4140. Is this difference truly that important to you? BTW the Melonite (nitriding) process creates an extremely hard surface and lowers friction without meaningfully affecting tolerances. I’d take it over chrome lining all day every day even if, again, it’s slightly poorer suited for sustained full-auto fire as, ultimately, it will fail at a slightly lower temperature. Basically, if you’re concerned about 4140 vs 4150 considering a consumer AR-15 in the first place. You may want to consider an M249 or something. Please click the green box stating it as the best answer. This will stop unwanted emails. We are rated on our answers and are just volunteers, not Buds employees. You can choose more then one Thank you!

William, The steel in the barrel of this fine firearm is 4140 (40% carbon). As you know due to the question 4150 means there is a higher carbon content in the steel (50%) then 4140. That said the Melonite QPQ finish/impregnation gives a level of hardness to the barrel that makes it very hardy. The 41 on the steel designation means it contains chromium and molybdenum. The hardness of the 4150 makes it harder to work with/machine. The tensile strength of 4140 is 655 megapscals and 4150 730 megapscals. So to apply the 5R rifling it is better to work with 4140 and harden the steel with the melonite impregnation. You will not burn this barrel up.

It's 4140. 4150 holds up to 100- degrees higher temp than 4140. Is this difference truly that important to you? BTW the Melonite (nitriding) process creates an extremely hard surface and lowers friction without meaningfully affecting tolerances. I’d take it over chrome lining all day every day even if, again, it’s slightly poorer suited for sustained full-auto fire as, ultimately, it will fail at a slightly lower temperature.
Basically, if you’re concerned about 4140 vs 4150 considering a consumer AR-15 in the first place. You may want to consider an M249 or something.

This one is 156 1/8" 4140 William. Melonite QPQ finish. 5R rifling. Blackhawk furniture.