So I've bought two AR lowers and I'm looking to build them for hog/predator hunting. Can y'all give me some advice on a few things?

Barrel length
Barrel twist
Is a bull barrel needed
Etc

Thanks

What caliber are you wanting to build?

I was planning on 223 but really at this point I can go anyway. I thought about one 223 and one 300 black out

More powder behind a bullet, lower twist rate, like a 1/7 twist. a 16" barrel is good out to a few hundred yards with the right scope. However, if I had the money to build whatever I wanted for hunting, I would build a 6.5grendel, 6.5creedmoor, or 6.8spcII, both have better ballistics than a .223/5.56 or a 300 blackout.

Can I build those with the lowers that I bought? I thought I was limited to the 223 or 300.

Your lowers can shoot just about any caliber you want. What matters is the barrel, magazine, and bolt carrier group/bolt.

6.5 Creedmoor will not work on an AR15 lower. It has to be on a AR10/AR308 lower. I would go with a 6.8 SPC for hogs, deer, etc.

You're right about creedmoor. It's only grendel in the 6.5 that will fit an AR15 lower. I second the 6.8.

I have a 6.8, 6.5, and a 450bushmaster the bushy is my go to porker gun. And It's a damn accurate gun, mine is punching inch groups At a 100

I put a 7.62x39 together, shoots great & you can shoot 30 caliber at hogs for .23 per round.

Both the 6.8 and 300blk would serve you well. Ballistics are very comparable, but the 300blk only requires a different barrel. All other AR components are common to both the 300 and 223/5.56.

Do you have a suppressor? If yes then 300blk is gonna make the most sense. If not, then the 6.5 grendel has the best ballistics of all the above mentioned calibers (excluding the creedmor because it wont fit your ar lower). I have 4 300 blackouts so I know what this cartridge can do and I love it, but it has limitations. If it were me I would do a 6.5 grendel. Better range and power than the 6.8spc. More suited to hunting. But the grendel needs at least a 20" barrel and the 6.8spc is best a 18". So all the above calibers are good, it just depends what you are going to do with it and personal preference.

No suppressor. Probably gonna build one 223 for the kids to shoot around with and then the other will be for hog hunting. I would like for the hog gun to be something that I can get the ammo for pretty easily.

6.5 GRENDEL, 6.8SPC, AND 300BLK are all pretty common online now.

I have been hunting with a 6.8 AR for the past 5 years and really like it. Ammo is also pretty easy to find at the local Wally World or gun shop. You could always get a couple of uppers chambered in different calibers for the same lower.

I'd highly suggest building a 5.56 and 6.5 Grendel. IMHO at least one 5.56 AR is a must. Stay away from the blackout unless you're running suppressed and really enjoy shooting paper really, really quietly.

The 6.5 Grendel is an excellent hunting choice for the southeast. Go over to the 65grendel forum and do a search on hogs in the hunting subforum. A user by the handle 81police has A LOT of pictures of really impressive hogs he has taken with his Grendel. There's really cheap ammo available from wolf for the Grendel and a lot of GREAT hunting loads available from $0.85 to $2.50 a round.

The 6.8spcII isn't a bad choice if you decide that's the route for you.

Barrel length
It'll depend on the cartridge and what distances you think you'll shoot at. As far as the Grendel goes you'll be good with anywhere from 11.5" to 20". A 16" would probably be your best bet.

Barrel twist
This will depend upon your cartridge choice, barrel length choice, then barrel maker choice.

Is a bull barrel needed
No not at all! For a target gun it's not a bad idea. If all you're going to do is hunt with the rifle, then I'd highly advice a light profile.

Why...300blk is a great little round for more than just poking holes in paper.

X2 ! Its a great round for hogs, PLUS if you want to run a 10 inch pistol you can AND it want bust your ear drums up like a 223 pistol.

You need to look at 458 SOCOM and 450 Bushmaster. If you can reload then 458 wins. 450 if you are going to buy off the shelf.