Currently have a Leupold VX 1-6x24 on my SCAR 17, which is ok but I had to send the scope in for repair due to the electronic red-dot center going dead sometime in the first 1000 rounds. I would attribute it to the gun. The optic works fine without the red dot though.
I'm now thinking of SBR'ing it to a factory 13" barrel and trying either the Elcan 1-4 or a straight EoTech red dot. As much as I like to play 'designated marksman' at the range, my bolt gun is the better tool for reaching out past 400 yards. And realistically, with the type of fighting that is likely to happen if and when civil unrest comes to my neighborhood (I'm only 30min from Kenosha, WI), it will probably benefit to have a true 1x and a fast handling setup than a DMR with a longer barrel and higher end magnification range. If I wanted to go that route, I'd buy either the Vortex Razor 1-6 or new 1-10. You may not be giving up much with the low end of 1.5x on the larger Elcan, but personally I'd rather have the true 1x.
If I was going to build the SCAR 17 like a DMR or long-ish range build (similar to a SCAR 20) then I'd probably think about a NF 4-16 or a ZCO 4-20. I've made hits easily to 600yds with the 1-6x, so the rifle is certainly capable if that's how you want to utilize it.