Same penetration @ 30 out to 55 yrds...why???

[Blue Moose CO]

I have noticed that I've been getting the same amount of arrow penetration on my target at 55 yrd as I do at 30 and 40 yrds. Why is this???

I practice out to 50 -55 yrds. I have always kept my hunting shots to 40 yrds or less. I have always thought that I wouldn't have the energy at further distances to kill an elk. Also that too much can go wrong with such a big arch (twigs/branches). Am I wrong about the lack of energy out to 50-55 yrds?

I don't think I would take that far of a shot even if I did have the energy, but having thatconfidence in my bow, is nice to have when I'm shooting at 40yrds.

Any thoughts or suggestions???

BM

[JeramyK]

BM, my guess is that it is probably nothing to do with your bow setup. It is most likely the target. At least that's my opinion.

Because the harder you hit something, the harder it hits back by the the square of the velocity. Kinda like if you jumped off a cliff into a lake, you probably won't go as deep if you jumped off a 12' tree.

Or maybe you have taken the challenge with a fellow rifleman, to shoot thru a 5gal bucket of water. An arrow shot from a bow sometimes can pentrate thru, but rarely will a bullet, especially softpoint.

With my recurve, I penetrate deer just as well as my compound, and sometimes better. I am shooting a 650gr arrow at 175fps.

[rybohunter]

Barring any inconsistencies in target media. It may have to do with higher frictional forces at higher speeds.

You are probably hitting a balance between the momentum forces of the arrow that want to keep it moving forward, and the friction forces of the target wanting to stop it.

[Centaur 1]

Somebody posted here recently how he chronoed his arrows at longer distances. I was suprised to learn that arrows don't slow very much, but it's the pull of gravity accelerating the arrow towards the ground the longer it's in flight that causes the arrow to drop considerably at longer distances. Somebody please correct me if I'm wrong but I think that's what I learned. If the speed is still there it should penetrate just as deep. I guess that I should have taken physics in high school.[&:]

[rybohunter]

You are right, and arrow falls faster the longer it is in the air.

But you still lose SOME speed downrange from air resistance.

When the arrow enters the target friction begins slowing it down. The faster it is moving the more friction is there to slow it, but also the more momentum the arrow is carrying to push against the friction. Farther out, the arrow is moving slightly slower, less friction to stop it, but also less momentum to keep it moving forward. I am guessing the ranges spoke of are where the speed is such that the momentum& friction forces are very close, allowing the arrow to penetrate equally over a range of speeds.

Or it could just be inconsistent target media and coincidence[8D]

Its not really friction of the target material but the surface tension that goes up by the square of the velocity.

[rhustek]

There is a link in a Momentum vs Kinetic Energy thread that will explain in more scientific terms what you are experiencing. Most of these posts refer to what is explained there, that the resistance an arrow encounters upon pentration goes up exponentially with its velocity. Since gravity is a linear force, meaning that the rate of change is constant through flight, you can probabably back up further than 55 yds and still get the same penetration. This will happen until the ratio of your velocity and mass changes drastically. Which by the way is the formula for momentum As I admittedly have previously made the mistake of arguing on the side of kinetic energy for penetration and not momentum!

Not starting another discussion here, just wanted to let you know about the link in the other thread.

[davepjr71]

ORIGINAL: Centaur 1

Somebody posted here recently how he chronoed his arrows at longer distances. I was suprised to learn that arrows don't slow very much, but it's the pull of gravity accelerating the arrow towards the ground the longer it's in flight that causes the arrow to drop considerably at longer distances. Somebody please correct me if I'm wrong but I think that's what I learned. If the speed is still there it should penetrate just as deep. I guess that I should have taken physics in high school.[&:]

I made the post about my speeds. The arrow was still at over 270 fps at 50 yds which is plenty fast enough with a 420 grain arrow for just about any animal. The issue with a shot that far is more with the animal moving by the time the arrow gets there then having the energy/momentum/penetration to kill the animal.

[The Rev]

Been tell guys that for ever about heavy FOC. I get better penetration at 30 than 20 shooting 543 grains.