Well, judging from things I have read some places we should have started at ground zero. Some folks don’t even know what a “shoulder” is. They think ‘shoulder” means the scapula, or the ball joint where the scapula and humerus articulate.
“Shoulder” is a collective anatomical term. It refers to an anatomical region (section) of the body; just as “hip” or “leg” does. The term “shoulder” includes all the tissues – meat, connective tissues and bone – contained in that anatomical region of the body.
The same terms are used in meat processing to refer to the same sections of the carcass. Here are some examples.
Here’s a processing chart for deer. The same entire region is correctly referred to as the “shoulder”. Note what constitutes the ‘shoulder’ region (section) of the body. It does not change from aminal to animal.
Now, if one is aiming ‘behind the shoulder” the aiming point would be where the white dot appears on the chart below. This is where every bowhunter education class I’ve ever attended (in the States) indicated as proper ‘behind the shoulder” shot placement.
When I speak of “aiming on the shoulder” I’m refering to an aiming point corresponding to the red dot on the chart above.
Here we have a deer standing broadside.
If you aim “back of the shoulder” the following will be your aiming point.
With an aiming point ‘back of the shoulder” this next diagram shows the size of the kill zone, before it first reaches a limiting edge of the thorax/liver area. Now think of the first movements a deer generally makes when it tries to “jumps the string”. It moves down and forward or down while turning either right or left. Think of where the deer’s body will be moving in relation to your kill zone. Use of this ‘back of the shoulder” aiming point is the major cause of hit too far back.
Using a ‘commonly used’ arrow setup, if you aim “on the shoulder” the following diagram shows the size of the kill zone, before it first reaches a limiting edge of the thorax/liver area. It represents a big gain over the ‘behind the shoulder” aim, and allows greater compensation for the animal’s potential movements when the shot is taken.
If you are using a penetration enhanced EFOC/Ultra-EFOC arrow setup having a mass weight above the heavy bone threshold the follow diagram shows the size of your effective kill zone with an ‘on the shoulder” aim. Because this type of arrow setup gives an ultra-high probability of penetrating any bone, or even any combination of bones, found in the ‘shoulder’ of a deer sized animal your kill zone is greatly expanded.
As shown, whether you are using a penetration enhanced arrow or not, the “on the shoulder” aim offers a greater zill zone than when you aim “back of the shoulder”.
Using an arrow setup that gives you the very highest chance of penetrating heavy bone offers other advantages, the above photos are all of deer standing broadside; which is not the most common shooting angle(s). Furthermore, the scapula is not always positioned as shown in the above diagrams. It moves as the position of the leg moves. That’s very likely where the advice to ‘aim behind the shoulder” originated. Here’s a diabram showing how the scapula moves as leg position changes. This particular diagram shows a bear, but the arc of movement of a deer’s scapula is virtually identical.
On some animals, sich as members of the swine and antelope families an aim ‘back of the shoulder” places you arrow extremely near the diaphram, giving an almost non-existant kill zone. Even with an ‘on the shoulder’ aim your kill zone will be small when using most ‘commonly used’ arrow setups, before the first limiting edge of the thorax/liver or heavy bones of the shoulder are reached. The following shows a ‘commonly used’ arrow’s kill zone with a “on the shoulder” aim on a pig.
Here’s what the kill zone looks like when you’re using a penetration enhanced EFOC/Ultra-EFOC arrow setup having a mass weight above the heavy bone threshold; a setup that is capable of reliably penetrating the heavy bones of a pig’s shoulder.
The “on the shoulder” aim’s location is best described as coming straight up from the leg to a point approximately 1/3 of the way up from the lower chest line.
Okay, now we have a common starting place for any discuaaion.