Ambi mag release and other parts.

[JulyAZ]

Top: standard lever. Bottom: extended lever. The pic's perspective makes the EMR-A with extended lever larger, the extended reach lever is 0.09" longer, but not taller.

Availability: May 19.

MSRP? Doesn't matter, I'm still buying one (at least) of the extended versions

[Duffy]

MSRP is $70, but do email me for an M4C discount code

EMR-A has two lever options as shown earlier. Just 0.09" of extra length makes quite a bit of difference in the pressure required to press the lever and drop the magazine. EMR-A, regardless of lever option, comes standard with an extra power (60% stiffer) mag catch spring.

I've long thought the standard spring (6.85lb) is too soft. A stiffer spring doesn't completely eliminate accidental mag drops, but does mitigate it. We tried 25%, 40%, neither seems much stiffer, 60% is a good compromise, it's noticeably stiffer but it won't wear out your finger from too much tension.

During the development of our EMR (mag release button), we measured the distance the mag release button travels before a magazine is dropped. On average, it is 0.07 or 0.08, in other words, not much. A magazine release button that protrudes over the mag release fence by more than 0.08 has rendered the mag release fence useless. For this reason, we include language to advise customers not to use our EMR-C (taller profile than the EMR, EMR doesn't protrude over the fence) for duty or combat ARs or M16s.

The above reason spurred us to look at ways to mitigate accidental / unintended mag drops. The result is the 60% extra spring rate spring that gets included in each EMR-A.

Note: do wear eye protection while installing anything under spring tension. The extra power spring can easily be launched into orbit during a mag release button or ambi mag catch installation, I guess there's no need to ask me how I know this

[titsonritz]

Looking good.

[556BlackRifle]

Dang. That's very nice. Only a few days away........

[Duffy]

EMR-A has been redesigned at least twice. MCS (Multi-faceted Control Surface) concept, where a control surface is contoured, or composed of flat surfaces of various angles, makes another appearance here. The idea is to place traction and contact area where they matter most, and where we don't want them (in order to channel / direct the user's hand or finger to contact surface and traction where they do the most good), both are reduced and minimized.

For instance, immediately below the bolt catch's lower paddle, EMR-A's lever is left very low profile and free of serrations, because we don't want the finger to wander there where it can do nothing. Serrations only start where pressure can be applied to press the lever effectively.

The serrated area is divided into 80% shallow V, and 20% straight. Where 80% transitions into 20% provides a natural index, and more traction, without making the lever any bigger than we want.





It started with the ABC/R, EMR and LDFA, and continues with the EMR-A. The EMR-A's original design was too costly and it looked like a spoon, but you can clearly see what we were trying to accomplish here.



Yep it's a piece of paperclip acting as a roll pin

[Duffy]

EMR-A is now available with standard (default) and optional, extended (0.09" longer) lever.

[JulyAZ]

Got mine in today. I opted for the standard level, and I'm glad I did. The standard lever feels natural, just like hitting the standard mag release on the right side of the receiver, there's not much to say it works as described without having to remaneuver your hand like I have to in order to hit the KAC release. My only "issue" with it is, it doesn't feel robust as the KAC it's definitely a thinner lever but nothing I would be concerned about. I'm anxious to see how it holds up. I'll get range time behind it this weekend, but it works perfect with the dry runs. I can for sure see this making it on other rifles of mine.

[Duffy]

JulyAZ, I'm glad you like it

One of the design goals of the EMR-A is for it to not unduly interfere with a standard bolt catch's lower paddle, which is something our ABC/R (bolt catch) aimed to address. But we wanted folks to be able to use their factory bolt catch without having to buy a new generation bolt catch, such as our ABC/R. The lever is billet machined from 7075, type 3 hard coat anodized, same method of construction and finish as our EMR and EMR-C (right side mag release buttons). Also, the lever isn't flat, the general profile of the lever is shaped like a side way I beam.

The pins used on the EMR-A are heavy duty coiled pins, and rated for 800lbs of shear strength. Because of the EMR-A low profile, a side benefit is that chances are very good if the rifle is dropped on the left side, it won't be the first thing that hits the pavement. The charging handle latch, sling mount, scope mount, etc. will see impact first.

KAC's ambi mag release lever is itself spring loaded and made of steel. The thinnest part (the leading edge of the lever) of KAC's is 0.81, the thinnest part on the EMR-A is 0.870. If it can be light and strong, then we don't need it to be heavy

[JulyAZ]

JulyAZ, I'm glad you like it

One of the design goals of the EMR-A is for it to not unduly interfere with a standard bolt catch's lower paddle, which is something our ABC/R (bolt catch) aimed to address. But we wanted folks to be able to use their factory bolt catch without having to buy a new generation bolt catch, such as our ABC/R. The lever is billet machined from 7075, type 3 hard coat anodized, same method of construction and finish as our EMR and EMR-C (right side mag release buttons). Also, the lever isn't flat, the general profile of the lever is shaped like a side way I beam.

The pins used on the EMR-A are heavy duty coiled pins, and rated for 800lbs of shear strength. Because of the EMR-A low profile, a side benefit is that chances are very good if the rifle is dropped on the left side, it won't be the first thing that hits the pavement. The charging handle latch, sling mount, scope mount, etc. will see impact first.

KAC's ambi mag release lever is itself spring loaded and made of steel. The thinnest part (the leading edge of the lever) of KAC's is 0.81, the thinnest part on the EMR-A is 0.870. If it can be light and strong, then we don't need it to be heavy

I've been sitting here messing with both the pictured lowers, the more I'm playing with it the more I appreciate the EMR-A. The finish is amazing, but I really downplayed how awesome coming from the KAC release which I viewed as the best in the Ambi-release just from the ease of use, using leverage rather than force to be the main way to operate the lever, while I still think that's the best thing the KAC has going for it, it's a huge factor for me that I don't have to completely change my grip and basically release my whole hold on the rifle to release the mag with the KAC, I might as well be using the right side release with how little control I have of the rifle during a mag change. This is something that doesn't happen with the EMR-A it so much more natural with a simple finger movement rather than your whole hand. This is huge. I hate the norgon and the Troy releases, this seems to get right what the others haven't not as big as the KAC which adds to the comfort, while not needing as much force as the others to operate. This is definitely more well thought out than it seems. Just like my LDFA, it's another great product I have very little to no doubt in its capabilities.

[Duffy]

Thank you JulyAZ

EMR-A's first design (pic of the white rapid prototype shown earlier on Pg. 5) was complete in 2015. It was redesigned in late 2016, originally changes to the serrated portion, which then necessitated a slight redesigning of the catch geometry.

The most significant change was the lever, including the serrated portion. In the early design, the area below the bolt catch's lower paddle was already lower profile, and free of serrations (to redirect the user's finger to the serrated portion of the lever, and to minimize interference with the bolt catch's lower paddle operation). The spoon shaped serrated portion would have been costly to produce, while it was form fitting, it just never felt like it belonged there.

The 2016 redesign is simpler, and feels right. The MCS (Multi-faceted Control Surface) existed on the original design, but is more eloquently and effectively expressed in the 2016 redesign. The 80% shallow V shaped, serrated length abruptly transitions into the remaining 20% straight serrated portion universally gets the nod.

You also brought up the leverage aspect. We used terms such as mechanical advantage and force amplification to describe the effect of using a lever, it is an area to which we paid a great deal of attention. It is directly responsible for the two lever lengths option, and partially responsible for the 60% stiffer mag catch spring that's included in the EMR-A kit.

I had long been convinced the mag catch spring was rather weak, and should be stiffer, considering how little the mag catch needs to travel before a mag is dropped. With the EMR-A, we wanted to make its lever easy to use, but not TOO easy as to become a liability for unintended / accidental mag drops. In this case, we deemed the 60% extra spring rate was the right number to make both the left and right releases require more conscious effort to press (but not too hard) to mitigate unintended mag drops, without quickly fatiguing the user's finger. We tried 25% and 40%, neither seems to make much difference, this is kind of telling of how weak the 6.85lb standard spring is lol.

EMR-A's paddle was designed without referencing other ambi mag catches, we wanted it to start from a clean slate, and whatever size and shape it ended up, it should be because it's the logical conclusion, not because we wanted it to be bigger/smaller, longer/shorter than anyone. As it stands, in terms of surface area, it probably has more of it than others. Too big a lever would make it easier to press, while too small a lever would make it harder, this part is almost impossible to get just right for everybody, so we started with the shape that's comfortable to use, while providing good traction. We added surface area where it matters, and removed it where we want to redirect the user's finger, the result is logically sound, it also does something quite difficult: feels right for all testers that used it, it exceeded our expectations.