I took my DD M4V3 out the other day and found the selector switch was having a hard time going from fire to safe with the bolt locked to the rear. It would go, but about halfway through the switch, the selector encountered good resistance. It wasn’t a problem as long as the bolt wasn’t locked back and went through smoothly if it was forward.
Specs: Daniel Defense M4V3, approx 200 rounds through.
Is this a normal problem (or even normal for that model) or something I should contact DD about?
It should feel the same as when the BCG is forward.
The only thing that should interfere with selector switch motion, barring faulty detent, is when attempting to put it on safe after the hammer has been released.
Open your receiver. Hold the hammer down with your thumb while moving the selector. Do you see anything out of the ordinary?
I ran into this problem with an RRA selector a few years back. Switched that part only with a Stag part and the problem went away. I think I recall Grant making a post about the channel the detent rides in having burrs cause the issue, but I could be wrong.
As others have stated, it should feel the same no matter where the bolt is. Just a thought, it could be something to do with the trigger bar that sits under the selector. If that is up higher than it should be it could be harder to move your safety, and the resistance felt could be the selector engaging this and pushing it down. It could be this way when its to the rear b/c the bolt on top of the FCG providing a little tension from above. I’d check my FCG out and make sure everything was GTG if I were you. Just a thought
I have a lower that does this too (not a DD). On mine I believe it’s a slightly out of spec lower as I tried multiple FCGs and selectors with no change. It works fine otherwise so I don’t worry about it.
Thanks for all the inputs.
This is a little phenomenon that is not common but not unknown. I have guys test for this in class because if you have it, there’s more to it that can go wrong than what you have experienced.
First let me coin a phrase. It might not be new, it might be known by some other term elsewhere / previously, but this is what I call it: overcock. It simply refers to the fact that as any hammer-fired system cycles the bolt carrier (or slide) back to rotate the hammer into the cocked position, naturally it rotates it a little further back than the final cocked position. In the case of the AR, it has to do this for the hammer to be caught by the disconnector which holds the hammer back until we release the trigger, at which time the hammer drops back onto the primary sear, if all is right (sometimes that doesn’t happen, a whole 'nother, and more common malady, resulting in “fire on release”.
Overcock.
If you look at your AR with the upper off, with the hammer in the cocked position, and then rotate the hammer back a little to simulate a bit of overcock, you will notice that the trigger moves too. That’s normal.
With the selector on safe, if you pull the trigger, you will normally get a little bit of trigger movement before the trigger comes to a hard stop on the selector shaft. That’s normal too.
Your safety is probably “bank vault tight”. In other words, with the hammer cocked and the selector on safe, you get zero trigger movement. Well and good until the hammer is held in overcock by a bolt locked back. Now things are beyond tight and into interferance-land. The hammer is held in overcock by the locked-back bolt, which is pressing the front of the trigger down, which is trying to rock the rear of the trigger up, but your bank-vault-tight fit between trigger and selector are preventing the movement.
Often enough it will put enough bind on things that cycling the bolt with the selector on safe will impede bolt carrier movement.
The solution is to remove a little metal from either the trigger or the selector where they meet when the selector is on safe. I don’t see where it makes much dif which one you modify.
Why does it happen? That old term “tolerance stackup” applies here-- you have so many things influencing this relationship that I reckon tolerance stackup could explain it-- or, who knows, one or more of the involved dimensions is actually out of tolerance.
I see this in approximately 1 in 200 AR’s. Can’t say that I’ve tracked which brands if any suffer from it more, but “fire on release”, again something much more common, definitely occurs more or exclusively in the lower-end brands.
Jeez, wouldn’t ya think people would check for this stuff before shipping a gun!?
That makes a lot of sense now. You factor in the position of the FCG pins in relation to the selector hole as well as the selector and trigger itself you have a lot of variables that can add up.
Good post.
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wow, exceptionally detailed answer. Thank you for that. While it appears to have gone away or at least diminished, I’ll contact Daniel Defense and see about getting it fixed.
Again, thank you for the very detailed explanation.
Thanks Ned for the interesting post! This is making me second guess ignoring this issue in one of my lowers. As I mentioned I believe the issue with mine is the lower since I’ve tried multiple FCGs and selectors. I believe the location of the trigger and selector holes in my lower must be slightly out of spec. On mine in order to install or remove the selector I actually have to first remove the hammer. I can leave the trigger in, just removing the hammer takes enough pressure off the trigger to let the back of it move down out of the way of the selector hole. I’ve never noticed any issues/binding when cycling the bolt while on safe and the lower has otherwise run fine.
Don’t think I want to attempt to file down the trigger or selector myself, wouldn’t want to remove too much metal. And I really don’t want to deal with sending the lower back and trying to get a replacement, but maybe I should…
My new DD V5 does the same thing. When bolt is forward it works fine. But with bolt back the selector is what I would call sluggish and you can feel it catching on something. I worked it back and forth several times with bolt locked back and it seems to not be as bad as before. I amnot overly concenred if it does not get better if it bugs me i will file a little bit of the metal off. No big deal…I guess.