For the ballistic reticle option, I recommend you head over to Nightforce and use one of their velocity reticles on a 2.5-10x. For your setup the LV600 should be the match-up. Another option is the Leupold Mark 6 with the 7.62 CMR-W reticle as it matches pretty closely to the 5.56 77gr at the velocities you'll run, and should do you well inside the ranges you want to shoot.
If you want to run a regular reticle, any of the above recommendations will be sufficient, budget depending. Pick your scope and the applicable durability/reliability to how hard you actually intend on running it, then start saving your pennies if the budget is an issue.
For me personally, I don't bother with FFP under 10x unless it's an optic that drops down to 1x, so don't worry about NEEDING the FFP feature. I've tried it, didn't use it or really like it either.
ETA:
SPR optics I've run so far: SWFA SS 3-9: Good overall, would prefer if it would have had zero stops, tunneled a bit at low mag loosing the wider FOV advantage, small but still useful reticle at low power, just less than ideal and I never used the mildots at low power. Sold it.
Leupold Mark 8 CQBSS M-TMR: Very good optic, not the best below 3x but still very usable including up close and personal. Awesome at top end and I love the turrets. Replacing it on my MK12 for a more spec build and going with a Leupold 2.5-8 TS-30 A2. The CQBSS is going over to my carbine .308.
S&B PMII 3-12x50: Ran this between scopes, way too large and heavy for this use. Decided to try and keep it under 25oz after this one for balance purposes, and going lighter still is better.
I'm building a second SPR/3-Gun rifle and am going with a Mark 6 for this one. I have both a TMR and a CMR-W 7.62 version that I'm going to test on it, and one will end up on the 16" carbine with the other going to the 18" barreled rifle. Sorry but I'm overseas and haven't gotten my hands on them yet to give you a report on those.
