Over the years, we've compiled an array of knowledge base on the AR selector, as one may expect from a manufacturer that makes what many consider the best AR selectors.  The information we're sharing here will be updated on a regular basis, please feel free to contribute, as it is applicable to not just ours, but AR safety selectors in general.

Let's make the selector a constant, these are the variables you should be aware of:

Receiver. Even well known and top flight receivers can have slight issues, no names will be mentioned, we have seen selector holes on the small side, selector holes not drilled evenly on both sides, or detent hole not drilled correctly. That said, buying a receiver from a well established company is the way to go, there will be a lot less consistency problems with these well known manufacturers.
If you believe the receiver may be the culprit, remove the trigger and hammer, install the selector (without the detent and spring).  At this point, the selector should not be binding on anything, and free rotating.  If it's binding something, it's binding on the receiver's selector holes.

Pistol grip. The spring hole in the grip can vary.  The deeper the spring hole, the less spring tension; conversely, if the hole is shallow, there will be more spring tension, and rotation will be stiff.  

If your selector is too stiff or mushy, and doesn't give you the kind of audible and tactile detent engagement feedback you expect, remove the lower from the upper receiver (making sure it's unloaded), remove the pistol grip screw, but leave everything else in the lower intact.  With the pistol grip loose, you can now move the pistol grip closer or farther away from the receiver to apply various amount of pressure to the spring to test if this is a spring tension issue.


If the rotation is mushy, and the detent engagement doesn't sound or feel positive when the grip is completely installed, or fully up against the receiver, you may need to add a spacer inside the grip.  We provide an extra spring with our kits for this purpose, you can clip off couple of coils from the extra spring to use as spacers.
If the rotation is too stiff when the grip is fully up against the receiver, you can try removing a coil of spring at a time, until the spring tension is reduced.

Trigger.  Trigger packs (not all of them) seem to cause more tolerance stacking issues than triggers of conventional design (hammer and triggers are not in an enclosure).  Specifically, the rear extension, or rear tang, of some trigger packs are a source of problems.  

The picture below illustrates the statement above:


On the left is a conventional trigger, on the right, an unnamed trigger that's a trigger pack.  Notice the height of the rear trigger tang on the trigger pack.  This particular trigger's rear tang needed to be filed down, or it would drag against the selector center's flat section.  Apparently the trigger manufacturer is aware of it, and advises as much.  Why not just fix the problem so it doesn't not require fitting on the user's part?  I don't know.

If you believe it is your trigger that's binding on the selector, remove the trigger and hammer, install the selector (without the detent and spring).  At this point, the selector should not be binding on anything, and free rotating.  Now put the detent and spring back, if it works as it should, you need to take a good look at the wear marks on the selector and trigger's rear tang.

Other considerations:

Detents.  We supply a high quality, stainless steel detent made by KNS.  We've included a new detent with our selectors since the second production run of our selectors in July of 2010, the reason we include it is because it's important to the selector's function.  A worn out detent will not help with rotation and detent engagement.  It is a wear item, it makes sense to use a high quality detent.

On the left is a KNS stainless steel detent, on the right is a detent that typically comes with a new rifle or LPK.  Notice the bottom of the other detent is not even.



Now, onto the selector itself:

Other than the selector center diameter, its center section flat diameter and the flat's width, here does not appear to be a set of specs that every semi auto selector adheres to.  This is evidenced by the various dimensions we found on selectors, with different detent hole sizes and shapes, different detent groove angle, depth and shoulder.  This explains the wide range of feel from factory rifles, the selectors don't come from a single place and do not have the same dimensions.  Selectors with very shallow detent holes may allow the selector to rotate past FIRE, onto where AUTO / BURST would be, though it will not fire in automatic or burst.  Selectors with shallow detent grooves are stiffer.  Billet selectors generally do away with these hit or miss characteristics, and they are generally smoother and more consistent.  This isn't a self serving statement, as Troy, JP, Noveske, etc. are all billet as well.

What it should look like  Under a magnifying glass, you can tell a great deal about it.

What it can look like (on the right), notice the shallow detent groove and shoulder depth.  On the left is the our first generation BAD-ASS, with deep detent groove and shoulder depth.  The latest design (pictured above) raised both the groove and shoulder depth.


There's noting wrong with the selector on the right, the problem sometimes is that often yours looks nothing like it, and will behave differently as a result.  

Below, from left to right, semi auto BAD-ASS, factory M16 selector, and BAD-CASS-3P, M16 (our M16 selector).



Notice the factory M16 detent groove looks nothing like the MIM semi auto selector, or ours for that matter.

I go into details about the detent groove depth, shoulder height, angle and detent holes because these dimensions are crucial, and very relevant to the function and feel of a selector.  I hope to shed light on why some selectors feel different, even though they all serve the same purpose, some just do it better than others due to the variables involved.

More to follow

I just wanted to say thanks for this trouble shooting guide.  My selector was very firm in my AX556 lower and I wasn't sure if I should start cutting up brand new parts to try to adjust it.  With the spring trimmed a few coils it feels great now.

Awesome, I didn't think anyone would bother to read it

So when my selector 'binds' some when moving from Semi to Safe, what does that sound like? I am using a Larue Predatobr 7.62. I checked the spring and it looks fine. Maybe I should reinstall the spring with the selector at a different position when I press the grip onto the lower? Thanks for any ideas you have on this.

Selector center's groove and holes don't wear nearly as fast as the detent.  You can try a new detent, if the symptom continues, install the selector on the receiver without the trigger group.  Some trigger's rear tang is taller than others, it's rubbing on the selector center when it rotates.

Do yo have an AR Gold trigger?  If the selector's rotation feels sluggish half way into the 90 degree throw, it's by design (AR Gold's design) Here's a video that explains the function of that design AR Gold video

Lastly, you can install the selector on another receiver and see if it still does that on there