I'll give a little of my thoughts here.
First off, subsonic. Even with bullets made to expand at subsonic speeds, a well placed shot is necessary, such as with the Outlaw bullets. At approximately 1050 fps, there is only going to be so much penetration with a bullet that is optimized for penetration and expansion. Hogs will drop in their tracks with a well placed shot in the neck or head.
As for supersonic speeds, the bigger the better. A .338 Lapua would work much better than a 5.56, 6.8, 300Blk or anything below it, but it is hard to shoot because of recoil and follow-up shots.
As for the 300 Blackout, surprisingly it isn't that much less powerful than a 6.8 in supersonic form. Some data from Wilson Combat:
Ballistic Performance Comparison7.62x40 WT (16” barrel)
110gr: 2534FPS Muzzle Velocity and 1569 Foot Pounds of Energy
125gr: 2463FPS Muzzle Velocity and 1684 Foot Pounds of Energy
5.56 Nato (16” barrel)
55gr: 3150FPS Muzzle Velocity and 1212 Foot Pounds of Energy
62gr: 3000FPS Muzzle Velocity and 1239 Foot Pounds of Energy
77gr: 2750FPS Muzzle Velocity and 1293 Foot Pounds of Energy
7.62x39 (16” barrel)
123gr: 2320FPS Muzzle Velocity and 1470 Foot Pounds of Energy
6.8 SPC (16” barrel)
110gr: 2550FPS Muzzle Velocity and 1594 Foot Pounds of Energy
300 BLACKOUT (16” barrel)
125gr: 2275FPS Muzzle Velocity and 1436 Foot Pounds of Energy
NOTE for Handloaders: Once a 7.62x40 WT case has been fired once it will be fire-formed and provide approx 1gr additional powder capacity and the potential for approx 25-50FPS more velocity at comparable pressure levels.
Now granted, this is a short list with average loads, and the 300BLK is only show using a 125gr bullet, whereas a 110gr bullet can be pushed in to the 2400+ fps range. I can push a 110gr bullet out of the 6.8 even faster than stated.
I've always made the argument that if you want a 300BLK, it should be used for subsonic use as there are much better options for supersonic use like the 6.8 and 7.62x40WT.
I own a few 7.62x40WT's and I'm not sponsored by WC or anything like that, yes I know Bill Wilson. But when I consider handloading, the 7.62x40WT used supersonic is a much more sensible option than the 300BLK. Case is still based on the 5.56 so cheap and easy to come by, forming the brass is a simple trim and run through a sizing die just like the 300BLK. But where the 7.62x40WT shines is that in my testing I can get close to 200 fps faster than a 300BLK, and nearly the same energy as a 6.8, so the benefit is that it is cheaper to use than the 6.8 (with certain stipulations identified below). Also, Barnes makes a 110gr TTSX bullet specifically for the 7.62x40WT (they make a similar bullet for the 300BLK) which are made to expand at lower velocities so you don't have to use .308 bullets that are made to expand at higher velocities of the .308 Winchester cartridge.
All cartridges require well placed shots, if you gut shoot a hog, it will run a long ways. With a better bullet like the 120gr SST out of he 6.8, they will expire quicker than any sub bullet at subsonic speeds or many other bullet/cartridge combinations. But of course a .338 Lapua would have even greater terminal effects than lesser cartridges.
Back to what this post is about. I use 208gr Amax's in my 8.5" 300BLK, but I've never shot a hog with it, someday maybe, just like I want to do with my AirForce Condor air rifle with a 31gr bullet going at 1100 fps, why, well because I know it do what I want to do with a well placed shot. You can watch Keith Warren take several hogs with .177 and .22 caliber Gamo air rifles, with well placed shots.
But, when we are talking general, shooting hogs on a regular basis and more than one at a time or running shots, there isn't a single subsonic round I would use because there are much better combinations that work better. Even a 5.56 with M193 ammo would perform much better.
So, can 208gr Amax at 1050fps kill a hog with a well placed shot, sure, so can my air rifle, but both are far far from optimal and require a well placed shot.
In closing, why shoot a hog with a well placed shot from a subsonic bullet, same reason I've shot deer at 700 yards, because I can. Would it have been better to get in to 100 yards from the deer to be more effective, sure, would also be better to shoot hog with a well placed shot, with good bullet, with a good cartridge, yes. But by numbers, the 5.56 takes more hogs each year than any other caliber out there. When we think in the case of the feral hog eradication, it is necessary by whatever means possible, but we still have to think about trying to do our best at whatever we do, and in that sense, a subsonic platform isn't the most logical choice. When considering supersonic ammo, factory loaded ammunition, choice of hunting bullets, AR platform for follow-up shots, it's hard to beat the 6.8.
