Because in essence "knock down" power does not exist. No rifle or handgun can transfer enough energy to actually "knock" a deer or person off from their feet. And no gun actually delivers or transfers the amounts of energy one believes it does. Numbers and math are cool, but just not realistic in most situations. I have seen it demonstrated various times on different objects and game.

I hunted one year with my shotgun using brenneke gold magnums. These are 600 grain slugs that deliver 3,000 ft/lbs of energy at 50 yards. I shot a deer in the vitals at 20 yards. 3,000 ft/lbs into a 175 lb object should have knocked it off it's feet and sent it sliding across the wet grass. Didn't happen, bullet went right through and the deer ran off and died 90 yards away.

Ok, I know what some are thinking, the bullet passed through so it didn't transfer the energy. Well wrap your head around this one then. I also hunt with an inline muzzle loader that uses a 350 grn polymer lead tipped bullet. When sighting in this rifle I shoot into medium sized pieces of fire wood. They probably weigh around 20 lbs. This load on paper carries 2000 ft/lbs of energy at 100 yards. Conventional thinking would lead you to believe this 20 lb chunk of wood would get thrown or at least rolled across the yard when hit at distances from 50 to 100 yards. Guess what, it doesn't even rock and the bullets are not passing through.

Knock down power is a myth, plain and simple.

Shooting a deer with any rifle does not guarantee that deer will drop in its tracks. It has more to do with shot placement and to some degree luck. You can shoot several deer in the same spot with the same cartridge at the same distance and they can all react differently. Some will drop on the spot, others will bolt and run a way, and others still will walk away seeming unaffected until they fall down dead.

Deer die from a gun the same way they will from a bow if shot in the vitals. They expire from blood loss and lack of oxygen the brain. Just because you shoot a deer with a rifle and it drops on the spot does not mean it is dead. It is just stunned by the shock to it's nervous or pulmonary system until it is too late. I have heard of several instances where deer have been shot, drop on the spot, then get up and run a way a few minutes later.

However you didn't physically knock the deer off from it's feet. You simply stunned it causing it to lose control and drop to the ground. Much like you would if you got shocked with an electric stun gun or hit hard in the neck. It disrupts your nervous system and you lose motor control. And just about any center fire rifle with the right bullet and proper shot placement can do this. But none of them can do it consistently every time.

What more energy and momentum will do though is create a bigger wound channel and give you deeper penetration depending on the type of bullet you choose. And this is what kills your deer. At 100-200 yards a 7mm mag is no more effective than a .243 is with a properly placed shot into the vitals or shoulder. Both will provide adequate energy and penetration to destroy the vitals and disrupt the nervous system at those distances. And a wounded gut shot deer is still a wounded deer regardless of the weapon be it a .22 rimfire or a 300 win mag. Larger calibers offer you the advantage of carrying more energy at longer ranges (do to the increased bullet weight) and offering better penetration on larger tougher animals.

Here is some more reading on it if you want to look it over.

The Mechanics of Terminal Ballistics

South Carolina Game study


My opinions anyway.

Paul