What do you intend to hunt?

For big game, the 30/06 is old reliable.

If you want something a little lighter in recoil the 6.5 Creedmoor will cover anything within its & your capabilities.

My personal opinion is yes, you need a new rifle that shoots a bigger cartridge.  If you want a rifle that is good for hunting anything that lives in Wyoming, one chambered in .223 is not it.   If the biggest game you want to hunt is deer and antelope, you can probably make it work.

If you want to stay with the AR platform, get one in 7.62x51 (.308) and you will be OK.  Get an AR with an 18 to 22 inch barrel though.  Velocity (distance) is your friend (along with a good scope) when hunting big game in the wide open spaces in Wyoming.

If you are not wedded to the AR pattern rifle, I would suggest a good bolt action rifle chambered in something based on either the 30-06 (30-06, .280 or .270) or the 7.62x51 (.308, 7mm-08 or .243, although .243 is light for moose & bear).  The scope you mount on your rifle should cost about as much as the rifle.  This set up will be good for hunting any big game found in Wyoming out to about 400 yards.

My opinions are based on hunting big game in Wyoming for 30 years. I have taken 2 moose, 20 elk, 25 mule deer and 4 antelope during that time.  I used a bow, a muzzle loading rifle (.54), a bolt action .270 or a single shot .243 for all of the big game I harvested.  So I do have a modicum of experience, but other peoples experiences way vary from mine.

Ok. Prepare for a barrage of things you never knew you needed to know about. I didn't start hunting until my 30s, and most Fish and Game sites are not at all geared towards newbie hunters who don't have a close friend/relative to guide them through.

5.56 is fine for many things, but if you want to go after the bigger critters you will want something a bit larger eventually. For now, I'd say stick with what you have and go after small game. If you like doing that, and you want to go after things bigger than deer/antelope, then go with bigger calibers.

Per the regs:
For the taking of antelope, deer, mountain lion, or gray wolf where designated as a trophy game animal, a hunter shall use:

(i)   Any center-fire firearm of at least .22 caliber (excluding .22 Hornet) and having a bullet weight of at least sixty (60) grains and firing a cartridge of at least two (2) inches in overall length, or any other cartridge of at least .35 caliber and at least one and one-half (1.5) inches in overall length, and using an expanding point bullet [.223 qualifies just fine, as does .357 mag and above]

You're good for deer and antelope with 5.56 and 60gr or heavier ammo.


For the taking of bighorn sheep, elk, moose, mountain goat or black bear by the use of a firearm, a hunter shall use:

(i)   Any center-fire firearm of at least .24 caliber and firing a cartridge of at least two (2) inches in overall length, or any other cartridge of at least .35 caliber and at least one and one-half inches (1.5) in overall length, and using an expanding point bullet.

For bigger game you want to step up a bit to say .243/6.5mm - 6.5 Grendel qualifies. The .357 in pistol or rifle form is still fine.

For the taking of a grizzly bear by the use of a firearm, a hunter shall use:

(i) Any center-fire firearm of at least .27 caliber and firing a cartridge of at least two (2) inches in overall length and using an expanding point bullet of at least one hundred fifty (150) grains.

Same rules for bison - 6.8mm/.27 or larger, with 150gr minimum bullets.

If you have a 12ga you can hunt everything in the state, with the caveat that you need to use a plug when hunting migratory game birds, must use buckshot or slugs for the bigger critters.

If you want to be a pistol hunter, you need .357 mag or a longer (overall length) pistol caliber above .35 in diameter, and you're good up to bison/grizzly. You want to go after those two, .460 S&W or .500 qualify, not much else I can think of - not a lot of 2" long pistol cartridges.

You need 4 things to hunt in WY:
1) Hunters ed class certificate, unless you were before before Jan 1 1966. Would strongly recommend you look into the classes now. You can also take the online hunters ed for Nebraska as that qualifies, and doesn't require an internet field day which is generally held in odd places. This is what I did, as I've hunted before and didn't want to wait until Jan 19 to see if roads were clear enough that I could drive to Torrington to take the internet field day. You might live close to a class or an internet field day, in which case that is probably the best policy. Be aware that the class is wrong about certain things, specifically caliber rules were out of date when I last looked at it a month back - look at the caliber reg I posted above to see the latest.
2) Hunting license for what you're going after - can buy this online with no problem. Also you must have the conservation stamp. Why this isn't automatically included in price I don't know - but get the $5 stamp along with the license. go here
Unlike some states there is not a blanket 'hunting license.' There is a license to hunt X. If you want to hunt elk and bison and moose you will need three different licenses. If you have a license to hunt bison, you can't hunt rabbits unless you have the small game license also.
3) A gun or bow adequate for hunting what you're after. Posted the caliber regs above. They're getting revised slightly this year, but only to be a bit more clear.
4) A place to hunt. State land is generally fine, aside from the state land parcels in major cities like Cheyenne. Once outside the cities, plenty of state-owned areas which are closed to recreational shooting but fine for hunting. There are also private land areas legal for hunting. Go here to go to hunt planner and look at available areas and game - there's also some ranches you're allowed to shoot in provided you follow directions there/ask permission.

If you've never hunted at all before, I'd strongly suggest getting the very cheap small game hunting license and go after rabbits - they are very plentiful, and you can use any caliber or gauge for them - centerfire, rimfire, shotgun, pistol, rifle, etc - you'll get experience hunting, snap shooting, and skinning/preparing the animal without lots of blood and special tools, without needing a meat processor, without needing a deep freezer. That way you'll find out if you really like hunting with minimal cash outlay.

Happy to help!
Also here is the land access map I wanted to attach but couldn’t locate. This one has state land areas identified, and lets you know which ones are closed to what activity.

WY list of mandatory calibers:
22lr
44 or 45LC handgun
5.56/223
22-250
270/3006/7mag/300wm (at least one)

After those anything else is fair game!

I have done all my big game hunting with 30-06.

That’s elk, deer, and antelope. Possibly buffalo if I can find one still.

That said I’m looking for a different caliber to shoot elk farther and for antelope not be so destructive.

My 30-06 says it drops 40 inches at 400 yards when sighted in at 100. Seems like a big drop.

I’m currently looking into 6.5 for longer shots on elk.

That all said 30-06 has done its job for sure. I’m essentially a self taught hunter and don’t have a ton of knowledge to bring to the discussion, but it has 4 elk, one deer and 5 antelope on that rifle.

I've shot antelope out to 425 yards around Cody with a 223 ar15. Just make sure the bullet is heavy enough. I've also shot them and deer with a 243 and 2506. I've shot deer and elk with a 270. Go with what you have and work your way up in caliber if you'd like. I did the opposite and started with a 270 and went smaller in caliber. My favorite caliber is 204 that I use for prairie dogs.

Good old 308 has done well for me...