It is my experience that all the energy from a pellet or slug hits the poi unidirectionally then breaks apart and bounces back from the paddle or faceplate multidirectionally.
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How Much ENERGY is actually delivered to a target struck ? ... A Conversation
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If the paddle was welded in place, in effect you are shooting against a flat piece of fixed metal and it would absorb 100% of the energy. If the paddle is hinged and moves rearward on impact it's not receiving all of the energy. Pieces of the pellet or slug would fragment to places unknown, but the power all of those bits and pieces retain was generated by the gun so it has to be subtracted from the initial FPE. You'd need to somehow get the wieght an speed of all the shrapnel,and do the math to figure how much FPE to subtract from your shot.
Glenn in Texas
Glenn in Texas
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I'll try again.
All that shrapnel is produced by the pellet releasing its energy upon the target. ie the target is taking that energy. I can't figure out why why we're talking about subtracting that from the energy exerted on the target. Chicken or the egg. If the target didn't take that energy, there would be no shrapnel, therefore the target took that energy.
And yes I'm following the concept of those tiny deflected fragments carrying energy themselves, but what about the idea that their energy source was absorbed by the steel upon initial impact and then deflected back into the fragments as they bounce off the target? I know it's tiny, but steel has an elastic effect (probably the wrong word).
Or consider a golf ball. The golf club has all of the kinetic energy on the swing, which it then imparts upon the ball at impact. The ball absorbs that energy and deforms slightly, then rebounds and takes off downrange "FORRRRE." If that golf ball exploded into tiny pieces flying in all directions when the club impacts it, we wouldn't say, "well there's pieces and they all have little bits of energy so the golf ball couldn't have received the full kinetic energy the club was carrying at impact."
All that shrapnel is produced by the pellet releasing its energy upon the target. ie the target is taking that energy. I can't figure out why why we're talking about subtracting that from the energy exerted on the target. Chicken or the egg. If the target didn't take that energy, there would be no shrapnel, therefore the target took that energy.
And yes I'm following the concept of those tiny deflected fragments carrying energy themselves, but what about the idea that their energy source was absorbed by the steel upon initial impact and then deflected back into the fragments as they bounce off the target? I know it's tiny, but steel has an elastic effect (probably the wrong word).
Or consider a golf ball. The golf club has all of the kinetic energy on the swing, which it then imparts upon the ball at impact. The ball absorbs that energy and deforms slightly, then rebounds and takes off downrange "FORRRRE." If that golf ball exploded into tiny pieces flying in all directions when the club impacts it, we wouldn't say, "well there's pieces and they all have little bits of energy so the golf ball couldn't have received the full kinetic energy the club was carrying at impact."
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Scott's question is how much of the projectile's terminal energy is absorbed / dissipated by the target.
Using the hypothetical numbers, we have 20fpe of energy available. After the projectile impacts the target and flies apart, that shrapnel departs with some modest amount of energy. There are no other sources contributing energy.into the reaction. The shrapnel has no other impetus from which to derive energy. Its energy is some portion of the original 20fpe. Thus we have to deduct it from the 20fpe to know how much was absorbed by the target.
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For similar caliber, mass, velocity, I believe that it's the hardness and shape of the tip that determines the amount of damage to a steel surface. Shape of the skirt? Does that really matter?
At 20fpe, which one would cause more damage? The softer "slug" with the flatter tip? Or the harder "pellet" with the pointed tip?
I did some testing for a target project that I was working on. All testing was with round nose 10gr .177@~900fp. Here are two examples of tested paddle materials impacted with 20fpe pellets. One is fairly soft mild steel (A36), while the other is even softer 2024 aluminum:
The steel had some damage, maybe acceptable but not good for long term (light cratering). The aluminum was totally unacceptable (heavy cratering). Testing on hard anodized 7075 aluminum was close to mild steel, while AR500 steel had almost no detectable damage (no cratering). The damage to the paddle is mostly determined by the relative hardness of the pellet/slug vs paddle. Same for the face plate. We did repeated (many) shots at the 6 o'clock edge of the A36 KZ to generate accumulated damage:
The edges of the A36 steel will peen over with repeated shots. Conclusion: If minimal damage over the long term is a goal, use AR500 steel for both the face plate and paddle, thick enough for the projectile and fpe. Probably 1/8" minimum for 20fpe pellets and slugs.
At 20fpe, which one would cause more damage? The softer "slug" with the flatter tip? Or the harder "pellet" with the pointed tip?
I did some testing for a target project that I was working on. All testing was with round nose 10gr .177@~900fp. Here are two examples of tested paddle materials impacted with 20fpe pellets. One is fairly soft mild steel (A36), while the other is even softer 2024 aluminum:
The steel had some damage, maybe acceptable but not good for long term (light cratering). The aluminum was totally unacceptable (heavy cratering). Testing on hard anodized 7075 aluminum was close to mild steel, while AR500 steel had almost no detectable damage (no cratering). The damage to the paddle is mostly determined by the relative hardness of the pellet/slug vs paddle. Same for the face plate. We did repeated (many) shots at the 6 o'clock edge of the A36 KZ to generate accumulated damage:
The edges of the A36 steel will peen over with repeated shots. Conclusion: If minimal damage over the long term is a goal, use AR500 steel for both the face plate and paddle, thick enough for the projectile and fpe. Probably 1/8" minimum for 20fpe pellets and slugs.
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*But the shrapnel of a projectile coming apart is not propelled by it's own mysterious power, it is propelled by energy extracted from the source being the initial 20fpe potential energy carried by the original projectile striking our hard surface.
Now I'm thinking this a no brainer we are missing something ?
Equal and opposite reaction per newton ... 20 FPE In and 20 FPE out absorbed back by the fracturing projectile ? If so the paddle would stand still as if the mid balls of a newton Cradle. Huh, that's not happening either.
Hell i have no idea, but the floated idea the target gets all 20 fpe simply does not stand up to this above *
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"How Much ENERGY is actually delivered to a target struck ? "
All of the energy is delivered but only some is accepted. For a particular target, we could calculate it for the spectrum of cases (completely elastic all the way to completely inelastic), but what will we do with this information?
Are we concerned with target damage or carrying the paddle over center and tripping the target? From a 20fpe pellet impact on a typical paddle mass, the paddle carries only about 0.01 fpe of kinetic energy.
All of the energy is delivered but only some is accepted. For a particular target, we could calculate it for the spectrum of cases (completely elastic all the way to completely inelastic), but what will we do with this information?
Are we concerned with target damage or carrying the paddle over center and tripping the target? From a 20fpe pellet impact on a typical paddle mass, the paddle carries only about 0.01 fpe of kinetic energy.
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We're in agreement. If 20 fpe is exerted upon a target at impact (based on speed and mass) than 20fpe is exerted upon the target. What happens after that is in question. Exerted versus absorbed might be the semantics at play here. By the time there's shrapnel, the energy that was carried by the projectile has been exerted upon the target. The shrapnel is AFTER the impact, a product of the impact. The impact is the release of kinetic energy that was being carried by the flying projectile into the target. That's where I'm struggling to understand why it gets subtracted.
The original question was if a slug will do more damage to a target than a pellet if they both start at just < 20fpe.
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Scott, It is somewhat obvious we have gotten off track talking about the event of impact and kinda find our self side stepping "IF or "NOT" a more structurally solid SLUG delivers or as you state, target "ACCEPTS" more input energy than a More fragile Pellet does at time of contact with surface ?
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I can agree with that. In Scotchmo's words, all the energy is delivered but only some is accepted...which is true of any inelastic collision (no perfect transfer of kinetic energy).
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Even with an elastic collision, there will only be a small percentage of kinetic energy transferred to the paddle. The rest stays in the projectile as it ricochets.
V...=velocity
M...=mass
For a 100% elastic collision:
Vpaddle=Vprojectile x (Mpellet/Mpaddle)
For a 100% inelastic collision:
Vpaddle = Vprojectile x Mpellet/(Mpaddle+Mpellet)
Because of the disproportionate masses, Vpaddle is about the same for either case.
kinetic energy transferred to paddle after impact = 1/2 x Mpaddle x Vpaddle x Vpaddle
Knowing that, what is the impetus behind the original question? Why do we need to know this?
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Are we overlooking the stored deformation energy, or the plastic deformation of the lead itself? It takes energy to change the shape of the projectile. So it would seem that some of the 20 FPE is put into changing the projectiles’ shape. The inelastic scattering of the projectile and it’s pieces account for the remainder in addition to the amount used to move the paddle. Just a thought.
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This might help some of you out. The again, maybe not LOL. We're discussing an area of post doctoral level research.
https://books.google.com/books/about/Impact.html?id=s9YoAwAAQBAJ
The subject is over my head.
I remember the author from my days at UC Berkeley Engineering. He had a long barrel in his lab that he used to shoot steel balls at square pieces of metal. It was basically a PCP.
FT
https://books.google.com/books/about/Impact.html?id=s9YoAwAAQBAJ
The subject is over my head.
I remember the author from my days at UC Berkeley Engineering. He had a long barrel in his lab that he used to shoot steel balls at square pieces of metal. It was basically a PCP.
FT
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20 ftlb is 20ftlb no matter the projectile. Which one retains it energy longer.....more often than not the slug. But neither will strike the target with 20ftlb of energy. You start loosing energy as soon as either projectile leaves the barrel. If you get quality targets it shouldn't matter. If they are rated to handle 20ftlb at 10 yards, then either projectile should be acceptable for use. Because it will always come down to target face material, paddle material, target mechanics, and strike angle. Way to many variables to pin down a single number figure.
At least in my mind anyway. But like was stated above...you may need to get NASA ot MIT on the phone.
At least in my mind anyway. But like was stated above...you may need to get NASA ot MIT on the phone.
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There is no possible way with today's technology that any FT target is receiving 20 FPE at any distance.
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The 20fpe number is arbitrary for the purposes of discussion. Call it 1fpe if you want. The question is about how much of the terminal energy is absorbed by the target.
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Hi guys, interesting discussion about the dynamics and physics of objects colliding. A fair amount of energy is dissipated as heat especially when metals are suddenly deformed. Anyone who has picked up a splattered slug can tell you - it's hot! If the targets are being deformed, then there's also heat dissipation there as well. And of course there is a tiny amount of energy released as acoustic but far below the main dynamics of impact.
This is kind of an end run thought process but this is just my problem solving intuition speaking.... if this whole discussion is driven by damage to field targets, then it seems to me the targets need to be made stronger whether it be different geometry or higher yield strength steels. The simple economics are going to stop FT clubs from just replacing all of their targets at once so something has to be done in the interim I suppose, but it seems to me if field targets are getting damaged then they need to be made stronger.
The shock and vibration of a projectile impact has a devastating effect on structures! An interesting compromise occurs when you have steels with higher yield strengths to resist deformation, they can become brittle and actually shatter so you need a metal with high yield strength and shock resistance. Now you're starting to get into tool steel territory which is arguably way more expensive than mild steel field Target components.
Perhaps cover plates and paddles can be devised from stronger steels and cut by flowjet to retrofit existing targets?
This is kind of an end run thought process but this is just my problem solving intuition speaking.... if this whole discussion is driven by damage to field targets, then it seems to me the targets need to be made stronger whether it be different geometry or higher yield strength steels. The simple economics are going to stop FT clubs from just replacing all of their targets at once so something has to be done in the interim I suppose, but it seems to me if field targets are getting damaged then they need to be made stronger.
The shock and vibration of a projectile impact has a devastating effect on structures! An interesting compromise occurs when you have steels with higher yield strengths to resist deformation, they can become brittle and actually shatter so you need a metal with high yield strength and shock resistance. Now you're starting to get into tool steel territory which is arguably way more expensive than mild steel field Target components.
Perhaps cover plates and paddles can be devised from stronger steels and cut by flowjet to retrofit existing targets?
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the slug and the pellet have to weight exactly the same (say 10.84 ) then are not we talking about the shape of the mass ? A slug has a solid mass and the pellet has a more hollow mass , I would think the more hollow mass would disintegrate easier with smaller fragments leading one to believe it exerted less energy . But the projectiles weigh exactly the same traveling the same speed and thus exerting the same energy to the target surface .
possibly aerodynamics has a role in this ?
possibly aerodynamics has a role in this ?
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Interesting read and I think there are parts to each post that needs to be considered. We're talking about conservation of energy. All energy in has to be equal to sum of the energy outputs. In this scenario I see three energy outputs:
Since the point of this thread seems to be about target damage, I would consider the shape of the projectiles tip to be important as well. A rounder or flatter blunter face will distribute the energy across a wider cross section of the target. A pointed projectile will initially start the energy dump for all the forces concentrated on a smaller cross sectional area - so there could be some damage to the metal with pointier projectiles. And at the same time the softness of the projectile matters too. Softer lead will deform easier so more energy will be lost in the deformation of the projectile. A harder lead my not deform as easily and transfer more energy to the target.
Something like this https://www.youtube.com/watch?v=ipQYWKRNZOI would be helpful here.
- The first is the energy absorbed by the paddle.
- Second (as @beerthiefe alludes to) is the energy required to rip the projectile apart.
- Third would be the energy of the projectile pieces flying away.
Since the point of this thread seems to be about target damage, I would consider the shape of the projectiles tip to be important as well. A rounder or flatter blunter face will distribute the energy across a wider cross section of the target. A pointed projectile will initially start the energy dump for all the forces concentrated on a smaller cross sectional area - so there could be some damage to the metal with pointier projectiles. And at the same time the softness of the projectile matters too. Softer lead will deform easier so more energy will be lost in the deformation of the projectile. A harder lead my not deform as easily and transfer more energy to the target.
Something like this https://www.youtube.com/watch?v=ipQYWKRNZOI would be helpful here.
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In practice, if both a pellet and the slug are starting with the same muzzle energy, the pellet will of course have less terminal energy because of its inferior BC. That part is easy.
Likewise I think we all know a softer projectile will do less damage to the target face than a hard one. This characteristic is intertwined with geometries that promote deformation and fragmentation more readily (e.g. hollow points). Energy deflected and converted to heat.
Caliber plays an important role. A .22 spreads the impact out over a 50% larger area than a .177.
How readily the paddle moves in response to the impact will have some influence, spreading out the energy delivery over a longer period of time. Meaning a sufficiently slow application of energy would cause little to no damage, but I expect this is an impractical thing to exploit to any meaningful degree.
Angle of impact is a big one. Tilt the paddles at a 45° angle and they will sustain a smaller fraction of the terminal energy. Of course that makes deflections/ricochets a concern.
Probably several other factors I’m leaving out…
Likewise I think we all know a softer projectile will do less damage to the target face than a hard one. This characteristic is intertwined with geometries that promote deformation and fragmentation more readily (e.g. hollow points). Energy deflected and converted to heat.
Caliber plays an important role. A .22 spreads the impact out over a 50% larger area than a .177.
How readily the paddle moves in response to the impact will have some influence, spreading out the energy delivery over a longer period of time. Meaning a sufficiently slow application of energy would cause little to no damage, but I expect this is an impractical thing to exploit to any meaningful degree.
Angle of impact is a big one. Tilt the paddles at a 45° angle and they will sustain a smaller fraction of the terminal energy. Of course that makes deflections/ricochets a concern.
Probably several other factors I’m leaving out…
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