1. The pig carcass was hung, it was not standing. As a Hunter, I can tell you that shooting a deer at 300 yards with a spine hit will not drop the deer straight to the ground. Instead in my experience it not only knocks them back and over but will spin them sometimes as much as 180 degrees from their original position. These shots made with a 200 grain .30 caliber bullet, so we aren’t talking massive projectiles. Now the point is that these are spine shots so we are talking about instant severing of the spine so there is no muscle reaction to speak of.

2. Distance should also be a factor in this test. At close range velocity of the round over comes the energy transfer of the projectile, the further away from the muzzle the lower the velocity (also energy as well but to a much lesser degree).

Now with these two things covered consider that a standard 308 using a 168 grain BTH projectile will knock over a 20 pound steel bull at 500 yards if hit anywhere above the lower 1/4 section of that bull. How is this possible? This round will leave the barrel at about 2700 FPS with an energy level just under that 2680 ft-lbs. At 500 yards the velocity has dropped to around 1800 FPS and energy to around 1250 ft-lbs.

As for actual recoil of this particular round in an 8 pound gun recoil is 18 ft-lbs and recoil velocity is 12 FPS. What many here do not seem to understand is that the projectile does not go instantly to 2700 FPS , it starts out slowly and builds its speed as the gas expands in the barrel. Using a barrel longer than 24″ will achieve higher velocities, roughly 50 FPS per inch, although there is a point of diminishing returns up until you reach negative returns.

The point of this being that yes if the transfer was instant to velocity then there would be a tremendous level of recoil from any round fire from any conventional rifle.

When you get into the difference between let’s say a 12 gauge shotgun slug and the 308 you also have to figure in the sectional density of the projectile the SD of the 308 round is around .270 while the SD of a 12 gauge slug is only .117 buck shot you divide
both impact energy and SD of the slug by 9 and what you come up with at the muzzle is 2361 ft-lbs of energy for the slug and 262 ft-lbs for the 00 buck and the SD for the 00 buck is .009 not much in the way of impact results except at the muzzle.