Unless they're fed supplemental proteins, as on a high-fenced ranch for hunting by (paying) clients, Texas whitetail deer aren't very big. Most bucks weigh on average 120-150 lbs. Does are usually around 90 lbs. That being said, shot placement is key, followed by using hunting ammo, rather than ball ammo.

I've killed a number of whitetail deer over the years, and my favorite rifle to use is my Savage 99 in .308 Winchester. That being said, the first deer I killed was a young buck with my Colt CRE-18 in 5.56mm. I made a high shoulder shot on him at 100 yds. with a 64 gr. Winchester JSP bullet, and he dropped like he was hit by the Hammer of Thor. I recovered most of the slug on the opposite side of its chest cavity where it had stopped against the skin (in other words, excellent penetration). Lots of people around here use the 5.56mm round to kill whitetail deer.

Unless you put a lot of accessories on your AR-style rifle, you have a lightweight, accurate, rifle with low recoil. I put together a PSA AR-15 in 6.8 SPC-II, which is the "next step up" from the 5.56mm to use as my MSR (Modern Sporting Rifle). I plan to use it this year on feral hogs and deer. An alternative would be to buy an upper in .300 Blackout or 7.62x39mm that would give you the ballistic equivalent of the .30-30 Winchester - which is a proven game getter.

To answer your questions:

1. Can a newbie hunt deer in Texas with a AR-15? I have the .223/.556 caliber AR Sport II.

Yes. There are no legal restrictions by TPWD (Texas Parks and Wildlife Department) that prevent hunters from taking game with the .223/5.56mm caliber. Be aware that a number of privately owned ranches that have paid hunts have a minimum caliber restriction of .243 Winchester.

2. Do you recommend I start practicing with a bolt action rifle for my first hunt?

I would practice with the rifle I plan to hunt with. Most deer around here (Central Texas) are taken within 100 yards or so. Every year I check the zero on my hunting rifles at the range before the season starts. I zero the rifle at 100 yards, and then make sure the scope is calibrated to shoot accurately up to 200 yards.

3. Where in Houston can I get good training with how to shoot accuracy at 50-300 yards for target practice?

I live about 4 hours away from Houston, so I have no idea what ranges are available in that area. I might suggest you find an experienced hunter to help guide and coach you. Yes, I know Al Gore invented the internet, and that there are a bunch of videos out there to watch, but I really think you need a guide/coach to help you out.

Good luck,

Dave