Gap between the receiver and selector levers

Dealers/ Manufacturers/ Regional/ Info Battle Arms Development
1

This is a subject that comes up now and then, so we’ll stick this here to serve as general information, as it applies not only to our own selectors, but all selectors.

There is a gap between the underside of the selector lever and receiver wall. The extent of the gap is a matter of receiver thickness.

We took measurements from couple of dozen receivers before deciding the length of the selector center.

What it comes down to is the thickness of the receiver. The milspec thickness is .880 +.015 -.002, or .878 to .895. We based our selector axis off one of my Colt SP1s, which is 0.898 and on the thick side. Even within the same company, there are variations.

This is a factory selector on an AR10

This is the prototype selected for production, after we’ve reworked the length of the selector center. The difference in amount of gap between the left and right is 0.01, the reference receiver is a Colt SP1.

CASS-3P, M16 (picture taken before our patent paperwork was filed to mask the patent pending dovetail interface)

Colt, Bushmaster Armalite, DPMS, LMT and KAC are all pretty well within specs. POF and another billet lowers are notably thicker, at 0.905 and 0.911, while Olympic Arms are notably thinner than specs.

There’s NO way to make a safety selector and have it fit flush with all brands of receivers, as mentioned, even within the same manufacturer there’s slight changes.

The same ambi selector that fits flush on a Bushmaster, LMT, and KAC will almost be too tight for a POF. With a standard, non-ambi selector, this isn’t an issue. If you haven’t noticed, the axis usually sticks out a little on the right side, while some don’t. This can be a problem for ambi selectors, too much protrusion on either side, it won’t be as low profile as can be, and the lever will pinch your finger when you rotate the lever from Safe to Fire while its extended in the “finger outside the trigger guard” position (this is actually somewhat unavoidable, we just try to minimize the pinching).

There is no problem with the lever sticking out and not sitting flush (it will never be flush, the original Stoner design calls for a gap between the lever and the receiver, and for good reasons). In terms of rounds fired, eight M16 with our selectors had 100K rounds through them in less than four months without any failure. Semi auto selectors have far more rounds fired, as there are more semi auto selectors in the hands of users :ph34r:

2

With the CASS-3P family selectors, M16 and the upcoming semi auto, the selector center will protrude a tiny more than the current semi auto 45 and 90 degree selectors. The reason is the female dovetail interface is on the tip of the selector center, and there must be enough clearance to ensure the male dovetail interface, which is on the bottom of the CASS-3P lever, does not come in contact with the receiver, or bind when there’s debris between the lever and the receiver.

The selector center must be sufficiently long to accommodate various receiver thicknesses from different manufacturers. If Colt made all the receivers, we’d be able to make ours more form fitting, alas the thicknesses are all over the place, making compatibility a serious issue we must address.

That the levers do not sit flush with the receiver isn’t necessarily a drawback. Levers that protrude further out have the effect of extending their usable purchase. On the flip side, the trigger finger side lever can pinch your hand while it’s being rotated from Safe to Fire, but in our experience, even when the gap is very small, pinching can still take place. It is then quite unavoidable, and the gap isn’t the culprit, the 90 degree legacy throw is responsible for that.

One might argue that such gap doesn’t exist for SIG, HK, FN, etc., this may be true, but remember these manufacturers do not have dozens of other companies making receivers for them, all with slightly different dimensions :stuck_out_tongue:

3

On the left, the original 90 degree selector, on the right, the CASS-3P, SA (semi auto)

Photo courtesy of jconsiglio :slight_smile:

Note that though the CASS-3P appears to stick out more, it’s only the selector center that’s longer than the regular selector. The CASS-3P’s center houses the male interface of the dovetail, and must be sufficiently long to accommodate a variety of receiver thicknesses.

In this picture, you can see the CASS-3P family of selector centers are longer than the original 45 and 90 degree, semi auto selector centers (left two)

4

Our selectors, M16 and semi auto, are designed according to receiver thickness specified by TDP. We’ve seen old M16 receivers that measure as thin as 0.61! :eek:

On these receivers, the sear pin sticks out on both sides of the receiver, with these receivers, unless it’s a special ambidextrous selector, the levers WILL stick out.

Photos courtesy of Cory F.

We will put a note on our site so buyers are aware of these huge variations on receiver thickness. When users contact us about the gap on receivers, they don’t always tell us how old these receivers are, only that they’re Colt or Bushmaster, nor do they tell us the thickness.

It’s assumed that all of the M16 receivers are done to TDP specs, this isn’t true. From 0.880 (current TDP specs) to 0.61 (probably a Vietnam era receiver), the difference is quite large.

We will entertain the idea of making a shorter center, but we can’t not make centers for 0.61, 0.75, and 0.81. While a center made for TDP spec will work on all of these, the reverse is not true.

I hardly think this is “poor engineering” on our part, as someone on TOS accused us of, rather it’s a misunderstanding of specs, and how the manufacturing date and year may factor into whether a receiver is CURRENT spec or not.

5

Somebody really said…that is “poor engineering” on your part on TOS?

Rhetorical question obviously because only shit that stupid would occur non face to face via the internet through the kiddie site.

If you accommodate these wankers by making different sized centers millions of sweet little babies will start crying all at once around the world.

Classic case of why you can never be perfect even when you are…thankfully it’s just the silly ass internet;)

6

Next time I will paint my fingernails for the photos…:lol:

I am not an engineer by any means but I know a few and I slept at a Super 8 or whatever the hell that commercial is, last night. I know quality when I see it. I have had engineers and machinists that work for Bosch tell me that the BAD A.S.S. is one of the finest pieces of machining that they have ever seen. One individual went as far as to tell me that if Battle Arms put the same effort into any other product that they made, he would not think twice about using it.

7

Bosch huh, that’s cool :smiley:

8

Duffy, I saw on another thread that you were finished with the M16 selectors?
Fill me in brother!
I am on vacation and the internet service has been hit or miss.
I have not forgotten about your last request and it is on my short list when I get home.

9

This week hopefully :smiley:

10

Whereas in the first few years when our selectors were purchased and used mainly by folks well versed in the AR, the availability and popularity of the selectors in recent months have reached customers that may be new to the AR system. The oft-asked question during installation regarding the selector is the seemingly out of spec length of the selector center (drum, axis). Folks familiar with the AR, but new to the ambidextrous selector ask this question as well, so we’ll share the info below for everyone.

When a selector is installed before the detent, spring, and pistol grip are put back on the lower receiver, the selector will be free spinning and OFFSET to one side or the other, usually the left lever is almost flush with the receiver, and the selector center protrudes a great deal out the right side of the receiver. This is because the detent has not engaged the detent hole or detent groove on the selector center yet, so the selector is simply sitting on one side of the receiver.

Selector lever flush with the receiver prior to re installation of detent, spring, and pistol grip:
Left side:

Right side:

Once the detent, detent spring, and grip are installed back on the receiver, and the detent is seated / engaging the detent hole or groove, the selector will be centered in the receiver, and the gap between the lever and receiver should be about even on both sides.

Left side:

Right side before the lever is installed

After the lever is installed

If you see a lot of selector center protrusion on one side of the receiver prior to putting everything back on the lower receiver, it is normal :slight_smile:

11

Thank you NSZ85 for posting this video that demonstrates
//youtu.be/NB5S6gM6PQQ