4150CMV vs. 4140CM

[speedy]

Have heard people argue that they would not buy a barrel made with 4140cm (chromoly) because it is not 4150cmv. The argument is that the 4140cm is not bad it just can’t shoot heavier than about 62g bullets. And the 4150s AR 15 barrels are not as susceptible to gas port erosion as the others, i.e. 4140cm(chromoly).
My understanding is that the 4150cmv steel contains more carbon than 4140cm. 4140cm has about 0.4% carbon/unit mass and 4150cmv has about 0.5% carbon/unit mass. Not a big difference. But, as a result the 4150cmv will have a higher hardness (and brittleness) after heat treating, while the 4140cm will be a bit more malleable. I can see this being an advantage on full auto AR15’s, or military weapons of course (which is used). But, most civilian barrels for hunting, plinking, and Ar’s are made of 4140cm.
What are your thoughts?

 

[Supermoto]

They both behave similarly until you really start doing long sustained fire with them. I haven't heard anything about them not being able to shoot bullets weights over 62gr

ETA: since the barrel makes or breaks the rifle. I would spend the extra coin on getting a quality barrel

 

[Jose]

My thoughts is that it would take too long to debunk the gross conceptual errors you have regarding steel alloys, their metallurgy, and their heat treatments.

Suffice it to say for now that unless you are doing serious FA dumps, the difference between 4140 and 4150 is meaningless.

One more thing, the alloy chosen has absolutely NOTHING to do with the bullet's stability in flight.

 

[bpm990d]

The carbon content of the steel has nothing to do with its ability to shoot a particular bullet. That is a function of the rate of twist.

The machinability of the steel does have an influence on the quality of the barrel. Badger Barrels uses a broaching process to rifle their barrels and if I remember correctly he uses 4150 because of its machining characteristics with that particular rifling process.

B

 

[speedy]

IMO unless you are continuously on the range, or in battle, the difference is going to be nill. I was just trying to bring up the topics and the points both of these individuals were making. I was just a listening to the conversation and intrigued me. Now, Any comments or info gained here is going to be part of "our collective knowledge".
Now, As far as "gross conceptual errors you have regarding steel alloys", I simply have no prior knowledge on steel alloys or the fine details this topic I am sure has. I am just commenting on what I have heard. As a Biochemist and researcher, I will definetly will read up on the subject, and bring myself up to speed. Thanks for the info. and "practical konwledge" you may have on this subject and for debunking any gross Ideas people may have. Nothing better than to "find a new itch to scratch".

 

[Jose]

Most of what you hear regarding metallurgy on gun boards is flat out wrong.

That goes for 4140 vs 4150, investment cast vs forged vs MIM, ad nauseum. Virtually all of the discussions on gun boards on these subjects are by people who have neither the education nor the professional experience to make intelligent comments about any of it.

It would be great if you would do the homework yourself.

This would be a good basic primer: http://www.moldmakingtechnology.com/articles/110002.html

 

[PatMcD]

Anybody arguing the merits of 4140 vs. 4150 really needs to take a step back and re-evaluate their life.

 

[Jose]

Anybody arguing the merits of 4140 vs. 4150 really needs to take a step back and re-evaluate their life.

That's about 99% of arfcom and m4carbine.net

 

[speedy]

Thanks for a good place to start. Appreciate your response.

 

[bpm990d]

There are a couple of places with good information about rifle barrel manufacturing and the materials used. Dr. Geoffrey Kolbe of Border Barrels has an article about the materials and processes that they use. You can read it of The Rifleman's Journal. Obermeyer Barrels also has some interesting reading about barrel steel.

B