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
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:
And then as part of the certification documents would be the chemical analysis to list CMV.