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Thread: Barrel Steel: 4150, 4140, Chrome Moly, CMV

  1. #1

    Barrel Steel: 4150, 4140, Chrome Moly, CMV

    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 can encompass 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 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 would be the chemical analysis to list CMV.

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  2. #2
    Join Date
    Jun 2008
    Feedback Score

    Lightbulb rifle barrel steel

    thanks for putting these test results up!

  3. #3
    Join Date
    Sep 2013
    Feedback Score
    thanks for the thread. definitely a good read. i work in a gun store who specializes in ar's and ar parts to get people parts for their own builds and so we have a pretty broad range of barrels, so things like this definitely help me with explaining the differences from one barrel to another. helps me do my job and helps me get good info out to people who are relatively new into the ar community and new to builds


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