From the very beginning, we're aware the EMR-A would be incompatible with battery assist device (Magpul BAD) levers. While these devices do facilitate locking and releasing of the bolt, they can cause problems on some setups. We don't know if there was ever a study/test to discover the right combination of receivers and parts for BAD type levers to cause a failure, but it's beyond the scope of our work, as we don't use, make, or carry any variant.
EMR-A's lever/paddle soaked up the
majority of the development resources, and it continues to be developed
in the form of new lever lengths and surface/traction treatment. In
view of the problems BAD type levers can cause, from very early stages,
incompatibility with them was deemed as acceptable. For the EMR-A lever
to work with a BAD lever, the EMR-A's lever would be drastically
changed, and these changes would quite negatively impact EMR-A's
ABC/R's development also disregarded BAD type levers compatibility for the same reasons.
RE: Geissele's Martime Bolt Catch compatibility, we've written about it on m4carbine.net http://www.m4carbine.net/showthread.php?197285-Geissele-Maritime-Bolt-Catch/page2 Below is a snippet of it:
The Maritime bolt catch was first seen in mid April of 2017, by then the
EMR-A design was well completed and working, usable EMR-A prototypes
were made in Feb of 2017. We thought it might be a compatibility
problem between the two, and indeed there is, as disclosed on the
EMR-A's product description page on our site, and earlier posts in this
To make the MBC and EMR-A work together, material would need to be
removed from either the top of the EMR-A paddle, or the bottom of the
MBC's lower paddle. Even then this would be far from ideal, the close
proximity of these two control surfaces will make both the bolt catch's
lower paddle, and the EMR-A's lever difficult to distinguish from one
another without a visual.
We took pains to separate the EMR-A's lever from the bolt catch's lower
paddle, it's indeed one of the key elements of the design. The area
directly below the bolt catch, the EMR-A's lever has the lowest profile
and is free of serrations, the design redirects the user's finger to the
serrated portion which is as far away from the bolt catch's lower
paddle as we can manage, without making the lever too long.
Maritime bolt catch serves a different purpose, which is quite different
from our own bolt catch (ABC/R). ABC/R creates a unique control
surface that can be easily distinguished from an ambi mag catch's lever,
while both its top and lower paddles have a great deal more surface
area than a factory bolt catch, they were not designed to have a
rearward bias, as left finger accessibility of the paddles (a fine motor
function) wasn't a design goal, nor essential for the ABC/R's function,
in any case it's not the reason for which the ABC/R was designed.
EMR-A, like all of our products, was designed for TDP
spec receivers, and to work with TDP spec components, and components
that don't deviate too greatly from TDP spec.
Geissele has its
reasons for making the Maritime Bolt Catch paddles the way it did. With
the ABC/R, we obviously differ in opinion on the extent of the paddle's
over sizing. Below is a post we wrote on m4carbine.net http://www.m4carbine.net/showthread.php?197285-Geissele-Maritime-Bolt-Catch
The Maritime bolt catch and our ABC/R are both bolt catches, and they
both have a larger upper paddle, that's where the similarity ends. As
mooseman stated, we had different approaches to achieve different sets
of goals, that's logical and proper.
Early on, military morons (MM) had suggested we extend the lower paddle
with a rearward bias, such a thing had already been done on AXTS's
proprietary bolt catch on their billet receiver. ABC/R's upper paddle is
already larger and twice angled (the upper paddle has a10 degree cant
at the lower 50%, and 15 degree cant at the top 50%, forming an "elbow")
and wasn't the focus for this discussion.
Our view was firstly, the location of the bolt catch's lower paddle
didn't present an issue for most users, and the upper paddle isn't meant
to be accessed with an extended finger that can only exert limited
pressure (compared to a thumb or palm) to the paddle, there's then scant
needs to create a bolt catch with extended paddles with a rearward bias
to enable it. Secondly ABC/R's design goal is quite different, it is
to address the issue of ambi mag catches obscuring/masking the bolt
catch's lower paddle, its angled and extra lateral protrusion more than
adequately achieves that goal.
Attention to detail is an
all encompassing policy that extends to areas many might overlook. Balancing a product's functionality with compatibility with 3rd party component is one aspect of it. It's virtually impossible to design a new product that's better than the original part it means to replace, and make it compatible with other components that rely on the original part's dimensions to work.