ESF (End plate, Sling Adapter, Forward Controls Design) is a drop
in end plate replacement for the AR platform (both 223 and 308 spec).
Featuring three quick detach sling swivel sockets (two side, and one
rear facing), when used in conjunction with a castle nut, ESF will allow
retractable carbine stocks to fully collapse. SOPMOD and B5 Systems
Bravo stocks will fully collapse with a rear facing QD swivel installed,
other carbine stocks must be closed on the #2 position on the RE (#1
position being fully closed) if a rear facing QD swivel is present.
ESF is available in 7075 aluminum, anodized ESF-L (0.39oz), and
4140 steel, DLC coated ESF-H (1.10oz) versions. Both ESF versions have
rotation limited side facing sockets. The rear facing socket has no
limiters, as the receiver extension effectively limits the swivel’s
rotation. From late 2018, non-rotation limited side QD socket option
has been deleted, all ESF-L and ESF-H have rotation limited side facing
We hesitate to call the 4140 ESF-H the “heavy duty” version, as it
implies the 7075 ESF-L is a “light duty”, which it most assuredly
isn’t. Nothing about ESF-L’s 7075 construction makes it a light duty,
it does make it lighter in weight. H simply means Heavy, L means light.
4140 DLC coated ESF-H is no light weight at 1.1oz, almost 3 times
as heavy as the 7075 ESF-L. Our design philosophy focuses on utility,
simplicity, and durability. 4140 ESF-H is heavy, because it is
practically bomb proof, and will outlast the 7075 aluminum receivers.
Our concern with weight is only limited to keeping our designs as close
to TDP weight as possible. There isn’t a TDP equivalent for the ESF,
and the 4140 ESF-H’s weight is centered on the AR, it will not cause the
weapon to be front or rear heavy, thus we deem its heft to be
acceptable, given its immense strength.
As is our practice, ESF’s shape is dictated by its functions. In
order to accommodate the rear facing socket, and fill one of the design
requirements that ESF must be able to use stakable castle nuts and allow
the carbine stock to fully collapse, ESF has a slight increase in width
on the sides, and small openings on the top of the sockets housing.
These design cues do not affect ESF’s structural integrity, and mostly
go unnoticed by users, they merely reflect a paradox, that it can be
quite complicated to create a simplified design. A seemingly simple
product can often be more than meets the eye.
Aesthetics were never a part of the stated objectives for ESF.
Nonetheless, ESF, like similar products before it, effectively lengthens
the carbine receiver’s rear and gives it a silhouette reminiscent of
the classic AR10/SR25. We’ve long considered the AR carbine’s rear
seems to be abruptly terminated, which leaves a gap between the end
plate and the carbine’s retractable stock. ESF fills the void and, the
classic AR15/M16 lines flow far better with it. Even though we take a
dim view of fashion firearms and components, we can still appreciate
aesthetics, especially if they stem from the design’s functions.
End plates that incorporate side facing QD swivel sockets can
mask available wrench notches required for torquing. A conventional
castle nut wrench has 3 lugs, in some cases, the socket housing may
partially block access to one of them. A 2 lug castle nut wrench, such
as the AR Multitasker, or our JCW (Joint Castle nut Wrench) would be
required to torque the castle nut properly.
ESF's receiver extension indexing tab can be tight on some receiver extensions.
ESF-L (7075) requires less force when staking than ESF-H (4140 steel), or TDP spec (1018 or 1020 steel) end plates.