I can’t speak to the .300 BO. I haven’t shot one, even on paper. But, I have gone on a couple of hog hunts using steel case Tula 7.62x39 ammo fired out of a Saiga, which is the civilian sporterized version of the Izmash/Kalashnikov AKM. I can tell you how the 7.62 on that platform performed from practical experience.
The hunt was in Cayuga, Texas at a lease. The Saiga used a cheap Walmart red dot sight with no magnification. I had a light mounted along the front handguard. I hunted a stand facing a clearing where the range was 70-100 yards out. I spent time at the range zeroing both the iron sights and the red dot. At range, the AK pattern rifle firing cheap combloc ammo was able to hit groups of about 3 inches. Not the 1-inch groups that AR owners are used to seeing. However, in pragmatic terms, that was plenty accurate enough.
If you are hunting for sport, you probably don’t take a shot at a hog smaller than a certain size. I waited for a 100+ pounder to wander into the field before I considered taking a shot. At that weight, you’re hitting somewhere lethal within a 1.5 inch radius of your aim point. You can either try for the heart/lungs, which is partially obscured by the large shoulder blade of a feral hog, or you can aim just behind the ear for a neck/spine shot. The risk with the heart shot is that the heart sits pretty low on the breast area, so if your aim is off or your rifle less than accurate, you shoot high - into a thick, bony shoulder blade that prevents a quick kill, or you shoot low, and just graze the underside and watch him run away. The risk with the neck shot is more about shooting high and sailing the round over the top of the neck. However, as thick as the neck of a feral hog is, you’ve got a few inches of body in any direction from the point behind the ear. You really have to screw the shot up to miss that badly. Hogs like to feed at dawn and dusk, so you probably have to take your shot in low light.
The light was low, and getting a good view of the lower silhouette of the hog’s foreleg/chest area against dark ground was more difficult from my vantage. The head profile and silhouette was clear, so I opted for the neck, just behind the ear. If the accuracy of the rifle/ammo was off by an inch and a half, it would’ve been the difference between hitting the brain, or hitting the spine, or hitting a bunch of circulatory/respiratory apparatus in the neck. My shot was about 75-80 yards, the hog was about 120 pounds. My light had trouble casting a great deal of illumination out that far, but it was enough to get a discernable profile of the hog’s head through the red dot optic. The hog was in a group, and it took some patience before he presented a clear enough shot, free of the smaller pigs. But as it was, I made a clean trigger pull and hit an inch off of where I believe I aimed. The hog went down instantly.
Feral hogs are ludicrously tough. You can watch the Youtube videos of them running off even after a good shot. For that reason, the lease I hunted at did not allow hunts with 5.56 ammo. Too small/not powerful enough and thus a safety issue. Plus it can affect the ethics of the kill. My father took a 135 pounder with a .308, and my veteran buddy knocked down a 125 pounder with a 7mm rifle. I gave my hog 20 minutes before I walked up on him. I could see how good the shot was, and that the hog had been dead still since he dropped. But when I got within 10 feet, the thing popped up, and tried one last gasp at running off. Made it two steps before collapsing again, at which point I shot it in the head with a .40 S&W sidearm to finish him off.
From your post, I gather you’d be shooting with a more accurate AR-pattern rifle, with a better optic with better magnification. You should be able to take a shot at 100 yards with either 300 BO or 7.62x39 and get a clean kill. You’ll get all the stopping power you need out of either round, so cost and your use case and personal preference are the main factors I’d guess. I opted for a cheap gun with cheap ammo for hogging, and frankly, it worked great. I’ve taken 3 hogs with that rifle, and only that one ever moved again after the initial shot. If cost is a concern, you can run a cheap rig as long as you properly zero the thing and plan on using it in the effective range. If you want competition-level accuracy, or you are going to take a 200 yard shot on a moving target using a 4 to 6 power scope, I’d say go for the 300 BO. But for my money, the cheap and slightly more challenging shot actually enhanced the quality of the hunt for me. The shots my dad and buddy made were practically cheating compared to mine. Each had at least a 4x scope at 100 yards at slow movers milling around a feeder. I had to pick one out of a crowd that was more agitated, and hold the trigger at the break point until he drifted into the right sight picture for a split second. Really fun hunt. I don’t think you can really go wrong with either cartridge you mentioned, given the rifle you specified. Either way, happy hunting and maybe let us know what you decided and how it went.