I run a full Sram Red drive train.

The rear shifting has been perfect, but I've had the "issue" that I think a lot of Sram owners had. When on the lowest gear in back (largest sprocket), trying to downshift once more causes a single click and resulting shift to the smaller cog. If I press pretty hard on the shifter, sometimes instead of a single click and upshift, I'll get a loud CLICK (really, a SNAP sound) and it will release causing no shift at all. It does take more pressure than normal to get that snap and release. It doesn't "feel" at all like a normal double-click downshift and really doesn't feel right, almost like something's breaking in there. I rarely do this though because I normally know I don't have any downshifts left and therefore don't try.

Last week I rented a bike with Apex. (BTW, very satisfied w/ Apex and will consider it for future economical build!). On that bike, with the same scenario, instead of either an unexpected upshift, or the SNAP and release, I got what felt like a normal "double tap" downshift type of thing and there was no movement in the derailleur. Normal shifting pressure, normal sounding and feeling double-click/downshift effect, but with no derailleur movement up or down. This actually felt much better, and "normal" to me.

I didn't have time to talk to the mechanic when I dropped the bike off to ask him if that was a specific goal in the low limit adjustment or not or if he'd ever noticed the SNAP type of deal I have with my drive train.

I've installed, adjusted, and re-checked adjustment following the Sram RD instructions exactly and have also viewed Youtube videos or Sram RD adjustment, and none of these things specifically addresses this.

Any words of wisdom? Thanks.

It's possible that you have the low gear limit set a bit tight. That causes excess tension in the shift cable, as it's stretched forcing the RD against the stop. Regardless of the brand a perfect low gear limit adjustment prevents overshifting of the chain intom the spokes, but is in fact a slight bit inboard of perfect trim. That allows the RD to move a bit beyond center trim for the shift and settle off the limit when the lever is released and it assumes riding trim.

Try backing off the limit a tiny bit to ease the cable tension to only that of the RD return spring. You should be able to manually push the RD in a hair (I mean it, only a hair) from it's natural low gear position. Double check that the limit will do it's job by shifting from the 2nd innermost sprocket to low, by pulling the bare wire away from the frame and making sure, 100%, bulletproof, bet-your-life-on-it sure that it cannot overshift.