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

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

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

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. ;)

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

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.

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

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.

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

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.[&:]

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

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]

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

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

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

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.

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

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.

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

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

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

I am confused.

Say you hit your target at the same place twice.

That would mean the target has a coeficient of friction X. Regardless how hard you hit that target, it is still going to give a coeficient of X.

The closer you are to the target, the faster your arrow is traveling.

The faster your arrow is traveling, the more energy is going to be transfered. (assuming same weight arrow)

So it would make sense that a faster moving arrow is going to out penetrate a slower moving arrow of the same weightbecause it will have a higher energy transfer. The faster moving arrow is at a closer distance (typically).

So tell me again why an arrow at longer distances will out penetrate at shorter distances?

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

Also, at distance, gravity works against your arrow.

Your arrow's KE is measured on a horizontal plane. Gravity works on a vertical plane.

The vertical down force will take horizontal force away from a moving object. Instead of moving in a pure horiztonal (x) plane, the energy will be split between two planes (x and y).

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

I think the issue is that nobody chrono's past 4 ft in front of the arrow and thereby believes that the arrow looses a lot of speed at distance. While this may be true for an object that is moving slow a faster object will still be relatively fast at a normal distance. 20 yds VS 50 or 60 yds. It's also true for heavy arrows that are already moving slower to begin with.

Most modern targets are made to use friction to stop the projectile. Therefore, the faster the projectile the more friction the media applies on it. However, this would not hold true on animals. You will not get better penetration the further out you are no matter what the weight of the arrow. Again, it defies all known laws of physics.

If you have 2 projectiles of the same weight and designmoving at 2 different speeds the projectile moving faster will out penetrate the slower one unless you use a media that is supposed to stop based on KE. When shooting at a game animal an arrow uses the broadhead to slice through and try to counteract the media trying to slow it down (animal hide, muscle, blood, etc). The slower object will come to rest faster.

This would be like using a 45 lb bow with a 600 gr arrow instead of a 70 lb bow and saying the 45 lb bow will out penetrate the 70 lb bow. We all know that is simply not possible. Yes, both arrows have the same weight but the 70 lb bow is shooting much faster and therefore will have more momentum and KE. This is why I always talk about people using the heaviest DW they can draw properly.

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

One thing that can cause you to have just as good or even better penetration at greater distances is tune.If an arrow has become more stable and is now flying straight with good vibration in the arrow,it will penetrate better than it would at closer distances if the arrow is trying to stabilize itself.

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

Very true and that's something that I didn't even think of mentioning and many people never think of at all.

Spine would have something to do with that too, correct? An underspined arrow will take longer to stabilize (if it does at all with a broadhead).

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

Yes,spine plays a MAJOR role in penetration and often times gets overlooked.

When I say tune,I include spine in that definition but some may not.Even though it is entirely possible to "tune" a bow with less than perfectly spined arrows.

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

Even an overspined arrow may take longer to stabilize and may penetarte better at 50 yards verses 35. IMO,though,it won't do as well as a properly spined,well tuned bow and arrow setup will.

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

True, I'll bet that 80 % of the people shooting today are not shooting well tuned bows or proper spined arrows. They only know what they have been taught, usually from other shooters that don't know squat about archery. I've seen it done in archery shops all across the U.S.

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

Very good point. It's interesting how ethical hunting slips past so many people.