For a place to start with your new rifle, zero near 200 yards. Then, do a search and study some about "maximum point blank range". You'll figger out what you want to do with it over time.
A very good bullet in the .223. It was developed many years back for 1:14 barrels, and it was/is a very effective fox bullet. I still have about 3 boxes of them left, (not for sale).Sierra has a 63 grain Varminter
Same load I use in my 223, which is a standard weight bolt gun set up similarly to my larger hunting rifles. A 1:9 barrel stabilizes this bullet fine. The trajectory of the 69 Sierra is close enough to my larger rifles that I :can practice up to 500 yards without the recoil and expense. My 22-250 is set up for varminting with a more suitable bullet.The 69 grain Sierra MK is a great aa-around bullet... Have been using it with 26 grains of W-748 for decades. Runs well under .5 MOA. It isn't the most explosive bullet going but kills PDogs to 500 yards.
Man, you guys are a way better shot than I ever even thought about being. I'm a fair shot at ~100 yds.; not driving tacks by any means but varmint size groups consistently. I don't think I could hit a building at 300 yds. let alone a varmint size target. In my area, we have a lot of woods/brush/small fields so the distances are not usually that far out for say coyotes. They usually stay along the edge of the fields for quick retreat into the woods. Very rarely do you catch one out in the middle of a field around here for a clear, wide-open shot at distances >200-300 yds. IMHO, all of the above is great advice. I also agree with @JBelk about zeroing at the average distance you plan to shoot and adjust from there. I do that very thing albeit at significantly shorter distances than what I have read here.I'm no stranger to shooting lots of prairie dogs with my Rem 700 VSF .223 with 1:12 twist, shooting Sierra 50gr BKs out to 300 yds. , but have always zeroed at 100 and practice at 200-300 yds.