When you are looking through the Brownells Catalog, there are
many different
parts and accessories that use the words Picatinny and Weaver
to describe what
they are compatible with. Just what is a Picatinny Rail anyway?
And how is it
different from a Weaver? It will be beneficial to look at the origin
of the
Picatinny system first.
The “Picatinny Rail” is a term that has evolved in
the firearm industry
from a military standard, specifically MIL-STD-1913 (AR) which
was adopted on
February 3, 1995. The title of the publication is
“Dimensioning Of Accessory
Mounting Rail For Small Arms Weapons” and this
document specified exactly
what the dimensions and tolerances were for any mounting
systems that were to
be submitted for acceptance by the military. The term
“Picatinny”
comes from the place of origin for this system, the Picatinny
Arsenal located
in New Jersey. MIL-STD-1913 specifies the dimensions required
for consideration,
including length, width, height, and angles and the tolerances
allowed for each
measurement. The key distinction of the MIL-STD-1913 lies in the
specification
for the profile and the recoil groove.
Source: MIL-STD-1913 (AR) 3
February 1995
Source: MIL-STD-1913 (AR) 3
February 1995
What are the differences between the “Picatinny”
and the “Weaver”
systems? The profile of the two systems is virtually identical.
Depending on
the quality of the machining done by the manufacturer, the two
systems should
be indistinguishable from the profile. The key difference lies in the
placement
of the recoil grooves and with width of the grooves.
MIL-STD-1913 (Picatinny)
grooves are .206” wide and have a center-to-center
width of .394”.
The placement of these grooves has to be consistent in order for
it to be a
true “Picatinny” MIL-STD system. Weaver systems
have a .180”
width of recoil groove and are not necessarily consistent in a
center-to-center
measurement from one groove to the next. In many instances, a
Weaver system
has a specific application that it is machined for, so
interchangeability is
not necessarily an issue. A MIL-STD-1913 system must adhere to
the specifications
listed above in order for it to be considered MIL-STD, since the
military desires
uniformity in the recoil grooves to allow for different systems to
be mounted
on the weapon with no concern for compatibility.
Now, what does this mean to you? Boiled down, it means that
accessories designed
for a Weaver system will, in most cases, fit on a
“Picatinny” system.
The reverse, however, is probably not the case. Due to the larger
recoil groove,
“Picatinny” accessories will not fit a Weaver
system. There are,
of course, exceptions to every rule, but for a good rule-of-thumb,
“Picatinny”
won’t fit Weaver, but Weaver will fit
“Picatinny”.