Alright guys, I need help. I want to get an AR built and I will mostly be using it to shoot pigs. I would also like to be able to kill big deer if the opportunity presents itself. I’m thinking an AR-10 chambered in .308 or .243. I have also looked at the .300 blackout AR-15s. Thoughts on what I should do?

And AR 10 going to be heavy.

What ranges do you envision doing most of your shooting within? I have used a 16" 300 blackout (AR15 as my go-to for pigs for several years now. Most of my pig hunts are stand hunting fields (150 yards max) or spot/stalk in the bottoms (10-75 yards tops). I've killed hundreds with it and have yet to have one run off that was not already running when I shot it. It's killed a few over 300 pounds and the farthest kill I've made was a tad past 230 yards. My 16" is 7.3# loaded.
I haven't hunted with an AR10, but my friend does. He's cut weight all over his 16" .308 and it's still almost 10# loaded. It also kills pigs very dead and maybe a bit cheaper ammo wise since he doesn't have to use the pricey Barnes bullets to get reliable penetration and expansion.
I do not personally like a .308 win shorter than 20". Your just giving up too much performance potential(especially in the AR platform) while still paying the weight penalty. I'd skip the .243 and angle toward the 6.5 Creedmore if going AR10. Now you have a very effective short or long range pig/deer cartridge. If you want to stick to the AR15, but need to shoot farther than 150 yards regularly, consider the 6.8spc or 6.5 Grendel. I have a 16" and 22" 6.5 G. The 22" comes in at 9.5# loade, prints .3 moa groups had surpasses my 30-06 at 500 yards.
Also, read into the ballistics of 300 blk vs 5.56 by barrel length. You can wring sufficient power from an 8-9" barreled pistol (or SBR if you want to go the NFA route) and have a dandy, light CQB type weapon.

Not nessasarfily a build but we put this one together. 6.5creedmore. We ordered everything from PSA. Weighs 11.5lbs with 10 rounds in the mag.

I would lean heavily towards the .300 blackout. Pretty good all around cartridge that will kill everything around here that you want dead. Easy to get ammo and the parts to build it yourself vary wildly from mild to extreme, only thing limiting you will be your checkbook. (Credit card for AU7.08). Light enough to carry around, sturdy enough to be a truck gun. My blackout is suppressed with a 14 inch barrel. Handy little rifle that goes with me every time I get in the ranger.

That’s nice

The next AR I build will likely be an AR pistol with one of those really neat braces in 300Blk with something like a 9" barrel.

7.62x39 for cheap shooting with a heavy hitter. Easy to find ammo
that out runs the 300BO.
A great deer/hog round if you choose to do so.

I won’t be shooting anything over 300-400 yards but 200-300 yard shots will be fairly common. We have some pretty large fields on our place. I worry about velocity and penetration with the .300 BLK at that distance. Would it be enough to take down a big pig or buck?

250 yards is pushing it for the .300 blk. Plus, even with supersonics, drop will begin to measure in feet rather than inches much past that. As I stated above, I've killed a big pig (@ 275 pounds) at just over 230 yards. Quartering away with factory Barnes Vor-tx right behind the shoulder. I recovered the bullet inside the front of the opposite shoulder. He dropped like a rock and stayed there. So the round, with bullets designed to expand at the lower velocities, will work within the effective range. You'll be best served with a 16" barrel if you are trying to shoot that far, though.
If you see a possibilty of 300-400 yard shots, the 6.5 Grendel in AR15 would be my suggestion. Or step up to any number of full-size cartridges.

I want this lower for a 300blk pistol.
http://palmettostatearmory.com/psa-ar15-complete-moe-ept-sba3-lower-5165448150.html?trk_msg=E1LT05JCK6749FB1ONLHHFS7QC&trk_contact=LS5KM1KI07MN59GM3DVEV7MQ1C&trk_sid=7NLBI17DFOKDGRC0ICTC12PFM4&utm_source=Listrak&utm_medium=email&utm_term=http%3a%2f%2fpalmettostatearmory.com%2fpsa-ar15-complete-moe-ept-sba3-lower-5165448150.html&utm_campaign=Daily+Deal+Email&utm_content=11%3a00+Email

I like this one

.224 Valkyrie is what I've been eyeballing for my next ar.

.224 Valkyrie is an amazing paper-puncher. Of course you'll have to drive out to 1200 yards to actually see where you are hitting.

My buddy just bought one. We haven’t had a chance to test it out though

Thanks for all the responses guys, really giving me a lot to think about. Somebody school me on the 6.5 Grendel. Never really heard much about it but it sounds like it may be what I’m looking for. Lightweight but also able to shoot at longer distances. Is it a relatively flat shooting round?