Well, since you asked.
The following is based on my own personal experience. I hunt on the ground so all my shots are at ground level.
In my opinion - If your foc gets below 12% and and are shooting standard carbon arrows (no fmj, grizzly sticks or heavier inserts) The energy in that arrow will get zapped real quick once it hits an animal because you don't have enough momentum. It may shoot great and group well and penetrate a target well BUT that changes on an animal.
All bows mentioned below are at 70lbs, 27" draw length. All arrow configurations were showing 72 to 85ft/lbs for KE. Also, when I tune my bows, I want my fixed blade heads hitting with field points at longer distances. IMO 30 yards isn't enough to tell me that. I will work to get my fixed blade heads and field points hitting together at 60 to 70 yards. Then I know my bow and arrows are set up correctly. Do I want to take those longer shots, nope.
scenario 1
several years ago I was a shooting a mathews helim. I also started playing around with a software program to build arrows. I ended up building an arrow using Carbon Express Maxima Blue streaks 350 using 125 grain slick trick 4 blade magnum broad head.
This resulted in a well spined arrow for the bow and I believe the arrow weight was around 415 grains and an foc of 15%.
I had a buck come out at roughly 25 yards and pretty much broadside. I aimed and sent the arrow. He turned just at the right time. My arrow entered right below that ball joint and to the right a few inches and exited in the middle of the opposite hind quarter and was a complete passthrough.
scenario 2
I picked up an obsession knightmare and built a new arrow - black eagle carnivore using their standard insert and a 100 grain QAD fixed blade head. Arrow weight was right around 400 grains and an foc of 13%.
Broadside shot at a deer at 20 yards - complete passthrough and took out a couple of ribs going in and out.
secario 3
I sold my helim and bought an xpedition excentric. I found through the software that the carbon express maxima blue streaks 350s (from scenario 1) with a 100 grain head spined out correctly for this new bow. Although it was a bit lighter at 385 grains and my FOC was 11%. Everything tuned great. Had great penetration on a target and they were flying great.
I did add a lighted nock to this arrow which brought my weight up to about 400 grains but dropped my foc some more.
Had a buck come in at 30 yards broadside. I took the shot and my shot ended up further back than I wanted. I don't know if I did something to pull the shot or if he took a step or some combination. At any rate,
I hit all soft tissue. No bones at all and it was right through the liver.
There was NO pass through on this arrow. I let him be overnight and started my track in the morning. He travelled 600 yards before bedding down the first time and that's where I recovered him. I found my arrow at 580 yards when he entered heavier brush and the brush caught the broadhead and pulled the arrow out.
With that in mind, what do you think would have happened using the above arrow and hitting a bone? If soft tissue stopped that arrow that quickly, bone will stop it even quicker.
At this point, I have the 2 bows - the knightmare and xcentric. I wanted to build a better arrow that would work with both bows, increase my FOC, increase my arrow weight but not so much that it really slowed the arrow down.
I really looked at the FMJ arrows but in order to get the spine right, the arrow ended up being heavier (over 600 grains) and significantly slower than what I going after. This wouldn't have been a bad thing, it just wasn't what I was going after.
I know the arrow speed isn't everything but I wanted to try to keep it at 280fps or better. I'm a short draw person so every little thing helps. Basically I was going for higher foc, more weight and to retain as much speed as possible.
After playing around with the software I settled on using the black eagle carnivores with a 42 grain brass insert and 125 grain head. This time I'm using Magnus black hornet 2 blade cut on contact with 2 additional bleeder blades.
With a lighted nock, this resulted in an arrow at around 450 grains and an foc between 16 and 17%. I was still getting decent speed out of the arrow and they were tuning great with both bows.
First up is the xcentric and the buck came out and was slightly quartering to me. 20 yard shot. Caught a rib going in and was a complete pass through.
This year I will admit I had this exact shot we are talking about (although he wasn't straight on like the pic above). I was using my knightmare and the buck came in and stopped at 30 yards. Where he was standing was also uphill from me. I sent the arrow off aiming for that pocket in front of the shoulder and knew he was hit.
I couldn't find my arrow around the shot area but with him being uphill from me I figured it would still be in him.
Found blood at about 10 yards from the site of the shot. I took two more steps looking for blood and picked my head up and there he laid. He went 25 yards.
After skinning and deboning him - here's what I discovered. That arrow took out 2 ribs and it did hit that ball joint in the shoulder. That head actually cut into that ball joint almost 1/4 deep.
The arrow still penetrated almost 26".
would an arrow at 400 grains with 12% foc or less have penetrated that far? - I'm guessing probably not. In fact, it may have only penetrated 4 to 6 inches and who knows about recovery.
Is a quartering to shot the best - no it isn't. Is it deadly, yes it is. We all want a nice broadside shot but those don't always present themselves. Even on broadside shots, things can go wrong on any shot. The deer can move, the arrow can hit a branch you didn't see, weed, whatever.
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Picture of that ball joint. This would have been on the front inside of the ball joint closest to the ribs.
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Broadhead held up up really well. Circled areas are a little damaged.