Coming from a guy that has just about every AR-15 caliber, and some very odd ones like the 221 Fireball and 222, I've used most on coyotes and will tell you 223 just doesn't cut it. It's great for a guy that doesn't have the funds to build different rifles and wants factory ammo. I suggest using what you have available to you now and save up and buy reloading equipment when you can. There's plenty of cheaper options to get started. I'm using 40-50 year old presses because they work very well for me. Being able to reload opens up so many options. Before I build a rifle, I buy 100-200 once fired brass and used dies. I don't care what anyone says, it's hard for the average guy to destroy a set of dies. Once you get the reloading figured out, the 22 Nosler would be my first choice, followed by the 6 ARC then 22 ARC. 22 Nosler Varmagedon factory rounds are sold on Midway for a very reasonable price if you don't want to get into reloading. The ARC's are great options with reloading because you can load lighter bullets. I'm running a 62gr Varmint Grenade bullet in my 6 ARC that is not very fur friendly, but shots that are off just a bit still get the job done. Reloading is also very relaxing and therapeutic for me. LOL