Why is 4150 steel better?

[Whytep38]

Who's scare-mongering here?

Given the discussion's context, I think these words "an AR is in fact a weapon you may some day have to bet your life on so get the real deal proven to be superior barrel" imply that one's life is at greater risk due to a steel-related failure if one's rifle has a non-4150 steel barrel.

If someone tells me that my life is at greater risk due to my choice of barrel steel, but that same person has no proof, that's scare-mongering.

[Robb Jensen]

I can see how that statement implies that whatever your choice of barrel is (if it's not 4150 CVM ) than it's substandard.

What I think every shooter should do is look at how hard and often they use their own ARs. If it's not anywhere near as hard as a full auto gun or 3gunner, then it's probably just money saved by using steels other than 4150 CVM.

[Whytep38]

What I think every shooter should do is look at how hard and often they use their own ARs. If it's not anywhere near as hard as a full auto gun or 3gunner, then it's probably just money saved by using steels other than 4150 CVM.

+1 to that. Given my current condition of health, a typical carbine class would damage me more than my AR. For any conceivable situation that would destroy my AR, I will be a goner before my AR is.

[Rifleman_04]

Well If I were in an extreme civilian/LE "shtf" scenerio and I managed to melt down/bend/deform/shootout the 4140 bl on my Bushy M4 somehow before my non-MP tested bolt disintigrated or I ran out of ammo while trying to break contact, provide suppressive fire, or mow down hoards of zombies I would pretty much be screwed anyways. As for general home defence, ranch type, trunk and plinking gun the 4140 is just fine.

But I sure am glad my issue Colt M4 barrel is 4150 CVM though.

[Whytep38]

Well If I were in an extreme civilian/LE "shtf" scenerio and I managed to melt down/bend/deform/shootout the 4140 bl on my Bushy M4 somehow before my non-MP tested bolt disintigrated or I ran out of ammo while trying to break contact, provide suppressive fire, or mow down hoards of zombies I would pretty much be screwed anyways.

I can see I won't be visiting your part of the world if the shtf.

If I understand correctly, M-1 barrels are 4140. Not to say that we should stick with WWII gear and technology, but just to add some perspective.

[jmart]

Well If I were in an extreme civilian/LE "shtf" scenario and I managed to melt down/bend/deform/shootout the 4140 bl on my Bushy M4 somehow before my non-MP tested bolt disintigrated or I ran out of ammo while trying to break contact, provide suppressive fire, or mow down hoards of zombies I would pretty much be screwed anyways.

That's some funny stuff!

[Drummer]

From the days when I dabbled in knifemaking...

SAE designated 4100 series are chromium/molybdenum steels. The last two letters indicated carbon (C) content. Therefore, 4150 would theoretically have more carbon than 4140. Additional carbon increases the hardenability of the steel, therefore, 4150 should be able to be hardened more (higher Rockwell number) than 4140.

Vanadium (V), when added to steel alloys, helps create a finer grain structure.

According to http://www.materialsengineer.com/E-Alloying-Steels.htm

Vanadium increases the yield strength and the tensile strength of carbon steel. The addition of small amounts of Vanadium can significantly increase the strength of steels. Vanadium is one of the primary contributors to precipitation strengthening in microalloyed steels. When thermomechanical processing is properly controlled the ferrite grain size is refined and there is a corresponding increase in toughness. The impact transition temperature also increases when vanadium is added.

And according to http://www.caffreyknives.net/content.htm

VANADIUM (V): Retards grain growth within steel even after long exposures
at high temperatures, and helps to control grain structures while heat treating. It is usually present in small quantities of 0.15 to 0.20 percent. Most tool steels which contain this element seem to absorb shock better that those that do not contain vanadium (V).

Therefore, 4150 with added vanadium should be able to be hardened to a higher point, and be tougher and more heat resistant (without damage/increasing the grain structure) than 4140.

[Shihan]

I have guns with 4140 barrels, I have guns with 4150 milspec barrels. This thread is starting to get into a "hey my 4140 is good enough for me" stuff and my non mil-spec steel barrel is fine for my use and it very well may be good enough for you but that dosent make the barrel superior just because it was in your price range and you wont be doing FA shooting. A semi gun can get plenty hot and when shooting high volumes in a short time will beat the hell out of anything and I would rather have the barrel that the gun was designed for instead of a cheaper alternative.

[Bill Alexander]

Unless you aim to hold the barrel at a temperature that exceeds the solution temperature for the alloy ie the quenching temperature for a significant period of time, the alloys 4140 and 4150 will behave in a near identical manner. It is virtually impossible to effect the grain structure of the steel at the temperatures found within even a heavily abused weapon. However the following are considerations in the selection of barrel steel

The 4150 CMV alloy will allow more margin for error if an overload condition occurs equally they have a much greater resistance to cracking if a heated barrel is suddenly quenched by seawater, snow, etc. This said M2 barrels have been seen with cracks running the full length following one of the rifling grooves from waves hitting a hot gun

At extreme cold levels the properties of 4150 CMV are desirable if the material is to exposed for significant time periods. It is this cold weather feature that is the primary driver in the material selection.

The selection of essentially a specialized gun steel over a commercial AISI grade is always preferable for a safety critical part. Unless the barrel maker can undertake both chemical and microscopic examination of a "rack grade" steel it is possible that the barrel is manufactured from a coarse grained alloy. This will impact the toughness of the finished part.

Bill Alexander

[mark5pt56]

Big question is, did you upgrade the good for nothing extractor spring and insert?

Well If I were in an extreme civilian/LE "shtf" scenerio and I managed to melt down/bend/deform/shootout the 4140 bl on my Bushy M4 somehow before my non-MP tested bolt disintigrated or I ran out of ammo while trying to break contact, provide suppressive fire, or mow down hoards of zombies I would pretty much be screwed anyways. As for general home defence, ranch type, trunk and plinking gun the 4140 is just fine.

But I sure am glad my issue Colt M4 barrel is 4150 CVM though.