Several years back, I picked up two sets of Armalite-pattern 80% lowers, with uppers to match. Seller (A well-known internet vendor) listed them as Diamondback Arms receivers.

Fast-forward to last night: I'm machining them and I notice that the selector detent hole (which was already machined when I got them) is 0.140" to the rear of where every print I found said it should be. I see this going three ways.

1. The entire FCG is moved aft 0.140"

2. The selector only is moved aft 0.140", and the tail on the trigger is long enough it still works.

3. The detent hole is in the wrong spot.

In the haze of already being set up and rearing to go (and not wanting to lose said set-up when day shift comes in the next day), I assumed #3, because I've had both AR15 and AR9 80%'s with that hole not in the correct location, just never off by that much.
When I install the grip....the hole was in the right place to match the hole in the grip. Shit.

So, does anybody know if either 1 or 2 is correct? Right now, my pocket and fcg holes are machined 'to print' which puts them in the same locations as an AR15 relative to the mag release and bolt catch features (at least, I think so). If they ARE actually 0.140" too far forward, will the hammer still hit the firing pin at correct-enough angle to fire and not break firing pins?
I don't have any barrels or bcg's yet, and never expected a problem like this with AR10's. Thanks for all advice.

Like a lot of us, you've found out that there is no "standard" print for large frame ARs.  Which one did you use for your dimensions?
I have a friend with an 80% lower that I am helping get the machining dimensions for, and have looked at several existing prints.  I'm using them, and a factory lower I have to come up with my own working numbers.  I am basing them off of the existing selector detent hole, but using the bolt catch slot as a secondary reference. (And yes, I checked the detent hole's location with the pistol grip)

I will try to check for the .140" set back on my factory lower (it's a Matrix Aerospace).

I wouldn’t move the entire FCG back.  That may put the hammer out of place with the bolt and firing pin.

Drilling a new detent hole may be tricky unless the new hole completely avoids the old hole.  You could try to fill the old hole with JB Weld, but if the holes intersect, you may need a mill to machine the new hole.  Otherwise the dill will follow the path of least resistance and you have an oval hole.

I’d drill the hammer and trigger pins, install them and then eyeball whether or not the relocated selector will still block the trigger.  If not, moving the detent hole is your only option.

Eta: The detent hole is .125” dia.  If the existing detent hole is .140” off, you should miss the existing hole. I wouldn’t bother trying to fill the old hole.  The enlarged 5/32” steps may slightly intersect, but the detent will follow the 1/8” hole.

I've contacted (who I think is) the manufacturer. We'll see what they say!

There's nothing like the idea of ruining some lowers by machining to print!!

How I have handled this issue when I have encountered it with the large frame 308 size 80% AR lowers.

This would certainly be the easier option, but I've always moved the entire operation based on the predrilled safety detent.

I purchased an 80% Ares Armor 308 receiver set years ago although I have not machined them yet I did a lot of research looking for a print and discovered there were a lot of variations. I have found three different AR10 drawings and the  relationship of the front takedown hole to the selector hole is different on all three. I firmly believe that the entire trigger pocket and FCG holes should be machined based on the detent hole location without changing any relationships. (This is making the assumption that the detent hole is in the right place, I think that the issue of the selector detent hole being in the wrong location is pretty rare.) I think that changing the relationship of the hammer, trigger and selector holes would cause a failure of the system to function correctly. As seen in the picture below the hammer will probably contact the firing pin in any case but it may not be square contact if incorrect.