The apollo reticle started on the SLx 3-18. I had one. The scope was nice, not nearly as nice as the 6-24 GLx I have now. IMO, a BDC has no place in a scope like that. Mil grid/tree style mo betta. After 600 yds the BDC was useless and a first round hit based off it really wasn't happening. Easier to just dial in elevation and hold for wind. On that note, because its a BDC, theres no indication of Mils in the reticle, it is all yards on the Y and wind speed mph on the X based on a 143 ELDX for the most part. So if you are low, you have a harder time dialing in when you miss because you cant just go "oh I was (x) mils low so I need to just come up (x) .1 mil clicks, and that is inconvenient.
I'll share a little homework I did for a bud who wanted that scope for his new bergara 308. The BDC is close enough out to 600 that it will work for most good 308 loads if you hold just a hair high after zeroinf at 100yd.