11595 Barrel Steel ?
4150 Barrel Steel ?
Chrome Moly Vanadium ?
4140 Barrel Steel ?


There has been a lot of discussions about some of the differences and some of the not-so-differences between these descriptions.  This post is in an effort to help clarify some issues as it relates to barrel steel.

4140 grade of steel – The “40” in 4140 is specific to the amount of carbon in the alloy.  Generally it is near .40%.

Likewise the “50” in 4150 steel is an indicator that the barrel steel has a carbon content near .50%

An 11595 barrel steel (Mil-Spec) gets its additional strengthening properties over the common commercial 4140 by one of two ways;
more carbon in the steel
-or -
more carbon with the addition of Vanadium.

The specific chemical composition of all Mil-Spec barrel steel is listed below in MIL-B-11595E.  This specification outlines the use of barrel steel under 2 inches in diameter for manufacturing barrels for small arms.  That encompasses a lot of different small arm weapons.


When purchasing steel from a mill the certification paperwork and other relevant paperwork usually lists a “Grade” of steel and then adds further details under the heading of “Specifications”.  For a Mil-Spec barrel steel; that specification would be listed as MIL-B-11595E.  This is to say that not all 4150 steels are considered Mil-Spec.  In order for it to be Mil-Spec it would need to be a 4150 grade AND it would have to comply with the specifications listed in 11595.  

Table One (listed above) shows three types of chemical compositions and ranges for Mil-Spec 4150 barrel steel as defined by 11595.  
ORD4150, ORD4150-Resulferized, and Chrome-Moly-Vanadium (CMV) should not be confused with the generic term of a Chrome Moly barrel.  My opinion and the opinion of the US Government (as defined by the Mil-Spec) is that one of the three is not better than the others.  They are all they same and are all 11595 (Mil-Spec) barrel steel.  In some descriptions used by steel companies I have seen the Grade of CMV further listed as 41V45, which is a bit more descriptive, but probably just add confusion in this context.

While doing some research on a project we are putting together in house, I was told by several reputable folks in the barrel business that Colt uses CMV.  I was under the general impression that Colt specifically used ORD4150.  Maybe I was programmed to think that way because it is all generally listed under the “Grade” of 4150.  So in order to have accurate data to work with, I submitted a Colt 14.5” M4 SOCOM barrel for destructive testing chemical analysis.  I received the results recently and that barrel that was made in November 2000 was determined to specifically be CMV.
(Results DT and chemical analysis document listed below)


 (As a side note, all weighted percentages were within the Mil-Spec range.)  This also matches the results of DT done previously on a FNMI barrel.  I acknowledge this evidence is anecdotal when applied to looking at all M16/M4 barrels, but it is interesting non the less.

So in describing a USGI (Colt) M16/M4 barrel it is generally done this way on spec sheets:
Barrel Steel
Grade: 4150
Specification:  Mil-B-11595E
And then as part of the Certification documents (certs) would be the chemical analysis to list CMV.

I hope this info helps . . .


edited to fix Molly spelling error

Quoted: What then is used in Bushmaster's 4150 barrels? p.s. I do not want to hijack this or turn it into a what is better than what thread. I am just curious to know if 11595 is the standard of all barrel manufacturers advertising 4150.

If I recall correctly, Bushmaster specifically advertises (on their website) CMV.
If their CMV barrel would contain the material listed in the first table and comply with Mil-B-11595E than it would be a MilSpec barrel steel.

Quoted: you destroyed a colt barrel?  wait until the kool-aid drinkers get a hold of you. great post none the less. thanks

ya, when they say Destructive Testing (DT) they aren't kidding

Quoted: Quoted: you destroyed a colt barrel?  wait until the kool-aid drinkers get a hold of you. great post none the less. thanks ya, when they say Destructive Testing (DT) they aren't kidding img.photobucket.com/albums/v445/bravocompanyusa/barrelpieces.jpg

LMAO!
Great thread man, very good info.
Thank you for sharing is all i got to say.
HUNTER.

Quoted: Interesting.  I use a Leco Glow Discharge Spectrometer at work.  They are normally used by foundries and other secondary metal manufacturers, I have never heard of an independent lab using one. I am trying to see how the people here are equating the CrMoV steel we see in the barrel to 4150?  AISI 4150 specs make no allowance for intentional vanadium additions.  To me, we have just learned that the AR-15 TDP probably does not, despite years of believing the contrary, call out 4150 steel.  It apparently calls for a specified CrMoV.  Just because that steel appears in the spec beside 4150 doesn't make it related to 4150.

We could have also opted for the test done with an ICP instead, but for this purpose the GDS will yield the differential information we were interested in.  This independent lab has the capabilities and facility to perform a variety of analyses.
I don't think folks are equating CMV and ORD 4150 in the absolute sense.  They are equal in the "eyes" of 11595.  In reference to mills and their distributors the term 4150 under the title of "Grade" describes a broader class of steel to include CMV.  I do understand what you’re saying, because ORD 4150 is not identical to CMV, especially in the AISI context.  Like I mentioned in the first post, I have seen CMV listed under a "Grade" of 41V45, but the more certs I page through that seems to be more of the exception and not the more popular the rule.  (Although it does seem more descriptive)  I do not know specifically why the barrel industry chose the terms it did.  Actually when you want the "good stuff" it is referred to directly as 11595 material.

There are tons of different Mil-Specs.
I am speaking directly to 11595.

Good stuff Paul! What steel will be used in your line of barrels?


C4

Quoted: Good stuff Paul! What steel will be used in your line of barrels? C4

DT showed us that FNMI and recently the Colt (shown in first post) was specific to CMV.
We will be using the same.

Quoted: Quoted: I read somewhere 4150 steel was used for M14 barrels way back..is this true?just trying to get a reference point when they started requireing this steel. It way have been, maybe not... what BattleRifle is trying to say is that a milspec like 11595 does not specify a specific steel, it gives a range of criteria that a steel must fall within to be "Mil-Spec", the 11595 is a generic ordnance steel for gun barrels -- is is not the only one however. The bottom line is that Tech Data Package (TDP) is the drawings, blueprints and detailed specifications for a particular piece of equipment, like the M4 and the TDP often states very secific requirements for what materials are used and how they are machined, tested and finished. A piece of equipment is milspec only if it made to the exact specifications of the TDP. I have the TDP for the M4 and can tell you that a great deal of the speculation people post of here is not accurate... but then, is that really a surprise? Here's the deal, nearly all of the barrels that are made by any of the names you have ever heard of are fine for what anyone on this board is going to do with it. If your need is greater, than someone that has the ability to, will buy and issue you the real deal.

Gunzilla
I have always enjoyed your posts . . . don't be stingy . . .keep 'em comin'

Quoted: Molly is a girl's name.

doh!

I just caught my spelling error . . .
gonna have to fix that  

Quoted: Does this mean the 4140 RRA uses is ( may ) be MilSpec, and as good as 4150 Bushy lovers say? H

A 4140 steel would not be 11595 milspec barrel steel.
Just as a note:  I don’t want this post to sound like a an advertisement for 4150 over 4140.
4140 is a very good barrel steel, a 4150 product is a bit better.  I own rifles with 4140 barrel steel and with 4150 barrel steel.   It is up to each individual shooter to decide what is best for them based on their uses and their budget for their rifle.