Heres what I can tell you from experience with my new Vortex scope , just like the one you just purchased. 12 power is all i have NEEDED to use from the day I first shot the scope. Granted , I only can shoot 400 yrds here at my home range, but it is so clear that I did not have to go any higher except to see my hits. at 12 ,the cross hairs are fine enough to get a real precise shot but not so fine that you lose them. Now understand, I am new to this whole long range shooting family, but , I have been doing alot of homework over the past 3 years on calibers, optics,ect. I chose a Tikka t3 in 270wsm. Sounds familiar doesn't it? Gun shoots great ! With hand loads , (140 gr. nosler ballistic tip,61 to 59 gr. of reloader 19, Win. brass and Fed 215 mag primers) under 1/2 inch at 100, 1inch at 200, under 1 3/4 at 300. Do yourself a favor, get the particulars of your load and use the ballistic calc. on the Vortex site, then use the trajectory validation and ,BOOM, you will have your drops out to what ever yardage you want. My first chart was only off by 1/4 minute at 400. Redid the calc. and set the m.o.a.'s to what the chart said and bingo!, DEAD NUTS ON! hope this helps you
P.s. Tikka is now a ground hog and paper puncher. by this time next year it will be re-barreled. barrel is very thin, cant get more than 3 rounds out before the barrel is to hot to touch and rounds go everywhere.