SAR 20#2

a qualifier of excellence or superiority- unless superiority
can indeed be found in uniformity and consistency. The
term “mil-spec” has become a generic descriptor, and is
often applied to any of the wares and materials purveyed
by today’s arms makers. And it is not entirely incorrect to
refer to a steel alloy applied or used per an established
mil-spec as “ordnance steel.” It is widely agreed that ordnance,
or mil-spec steel refers to a specific family of steel
alloy; chrome-moly, such as 4140. The enforcement of
standards and uniformity is absolutely necessary to ensure
any amount of quality and reliability in any system.
Today all metal alloys are given a title or numerical designation
from one of the authorities on metallurgy and engineering,
the SAE, and AISI. These material names and
designations describe a recipe or physical and chemical
properties. So a steel may be described by what it actually
is, as is the case with 4140CM steel, the 4 digit label
indicates general type of alloy, and the precise levels of
other additive elements to make the steel.
In actual terms, depending on the manufacturer of a
gun or its components, the terms Mil spec and Ordnance
Steel may be used to describe any of the following (but
not limited to); 4130, 4140, 4145, 4150, 4320, or 4340
chrome moly alloys. The truth of the fact is that ANY steel
may fall into the category of being “mil-Spec” provided
that it satisfies the criteria set forth in the military standard
for operating and yield strength for a specific application.
There is a tendency for gun manufacturers to use misleading
descriptions of their steel and its capabilities in
order to promote sales. All steels are not created equal.
This sales tactic can put the gun and its user at risk. All
steels are not created equal; beware of the fly-by-night
startup gun company that professes tactical supremacy
but omits the metallurgical details of their operation. That
said, modern firearms components from reputable sources
(as are most things engineered) are designed with a
“safety factor” in mind. Any gun barrel today should be
designed with a minimum 1.5 safety factor- which means
that barrel is designed to endure 1.5 times its intended
operating load before failure or fatigue. The “mil-spec” for
a steel structure usually demands a factor of only 1.5.
Commercial engineering often requires a safety factor
of 2.0 or higher. One should also be wary of the claim
of “aerospace” in firearms design. The tolerance, safety
factor and quality assurance by aerospace standards all
become prohibitively expensive and ultimately restrictive
to the end user. Aerospace grade demands a total detailed
and documented control and trace of material from
creation through use and operation. Nothing about your
rifle is aerospace grade.
On to the specifics of the steel that may be encountered
in the modern small-arm. There are only 4 general
types of steel; carbon, tool, alloy, and stainless. All material
that can be described as steel is one of these. The
creators of steel add various trace elements to iron to
achieve desired properties. All steel contains between
.25% and 2.5% carbon, which allows the base iron to be
chemically or thermally manipulated with or without the
addition of other alloying elements. To earn the rank of
stainless, the recipe of that steel must contain at least
11% chromium. Chrome moly alloy steel does contain
chromium, but not enough to be stainless. And all stainless
steel is not totally rust resistant. Some stainless is
highly magnetic. It is doubtful that one will encounter a
low carbon or plain carbon steel on a gun today; industry
lawyers and a general concern for safety have well
established a minimum for safety standards. Tool steel
is capable of being very hard and tough, but is more difficult
to craft. It may be used on guns in small amounts
to form items like trigger parts or lock components. One
SAR Vol. 20, No. 2 82 MARCH 2016