Explanation of Lehigh Bullets.
Mar 26, 2009 19:07:50 GMT -5
Post by grouse on Mar 26, 2009 19:07:50 GMT -5
Tom,
Thankyou for the inquiry on why Lehigh Bullets uses brass instead of copper. I thought I would expand this to also include how the Lehigh bullets function. The design aspects of a good hunting bullet include: accuracy, initial penetration, expansion/energy transfer, organ destruction, and final penetration/perforation.
Accuracy
Accuracy is important for terminal performance as the bullet has to get to the intended location. Lehigh bullets are machined from barstock on cnc lathes. The bullets come off the machine complete with no secondary operations. The bullets are machined at around 8,000 rpm. Due to the bullet being formed while spinning, the concentricity of all the features is inherent in the process. The hollowpoint is centered on the outside diameter and the wall thickness is equal all around the bullet. This means the center of the geometry is equal to the axis of rotation which makes for an accurate bullet. A formed bullet, either a jacketed or formed solid copper bullet is made in a static process, it is not spinning. Manufacturing and tooling tolerances make it very difficult to keep the internal features like the hollowpoint at the true center axis. Most o these bullets are also produced on a press that may form 10-15 at a time. Each of those bullets have the potential for being slightly out of balance due to the different tooling each one sees. I am not stating you can not make an accurate bullet through the forming method; I am just stating it is easier to produce an accurate bullet by machining. The downside of machining bullets is the cycle time. Machining yields somewhere around 120 bullets per hour while forming can yield over 5,000 per hour.
Initial Penetration
The bullet must be stong enough to penetrate the animals hide and muscle boundary before expansion begins. Factors for consideration include the bullet weight, impact velocity, and the animals structure. Due to these variables, bullets have to be designed based on estimated averages which induces performance issues when game is taken at the extremes of where the bullet designers thought the bullet would be used. This effects all manufactures. Machining a bullet from brass enables us to very quickly change the design features like the hollowpoint and then test the result. Since the parameters are controlled by cnc code, it is very simple and fast to change from one design to another enabling the testing of many configurations in a single day to quickly arrive at an optimum design. This process takes much longer on formed bullets as changes are tooling dependent. New dies and punches must be produced for each trial and the equipment must be then setup and centered making it a long process to try to get to the optimum performance level. The investement in tooling is very large and that is why you may find a formed bullet manufacture producing a poorly performing bullet for sometime before changing the design. The tooling and machine may also limit the formed bullet manufacture on how strong they can make the nose for complete initial penetration. The forming machine may not have the power to form a jacket with sufficient wall thickness resulting with a bullet that begins expansion upon contact severly limiting the bullets terminal performance. Machining a brass bullet to any wall thickness is very simple.
Exapnsion/Energy Transfer
This phase of terminal performance is very similar in a Lehigh brass bullet and a copper or jacketed bullet. The process begins as the bullet contacts the animal and completes when the bullet is fully expanded. The nose or metplat, determines the initial energy transfer. Big, flat noses transfer an extreme amount of energy. Depending on the impact point, this energy may be sufficient to shut down the animals nervous system. While a large flat nose is the best design for intital energy transfer, it lowers the ballistic coefficient of the bullet resulting in velocity loss and making it more susceptable to wind conditions.
Upon penetrating the hide and muscle layer, the bullet encounters tissue with a greater liquid content. This hydraulic pressure in the hollopoint cavity causes the nose to expand transfering additional energy to the animal. Expansion is complete when the upset growth stops which on a jacketed bullet could be a partial expansion or when the nose is completely folded back around the shank. Assuming a .500" diameter jacketed bullet, expansion may reach a frontal daimeter of 1.00". Lehigh bullets start expansion much in the same way. The bullets are designed to begin expansion upon the resulting hydraulic pressure. The nose petals are then designed to split the web of material between them. Once the petals achieve an angle of slightly less than 45 degrees, the petals separate from the base and radiate outward on independent trajectory paths. Remember all components of the bullet are still spinning.
Organ Destruction
In this phase there are some very distinct differences between a conventional formed/mushrooming bullet and a Lehigh brass bullet. As the Lehigh bullet's petals radiate outward, additional energy is transferred by each of the six petals. The petals have sharp cutting edges, and coupled with the spinning action, they are devastating to all tissue encountered leading to massive organ damage. The radial pattern will normally extend over 10". A customer recently tested the bullets on a bison and using a metal detector found petals 18" from the base path. Organ destruction was enormous. Often there is sufficient enrgy in the petals to penetrate the offside hide. A convetional mushrooming bullet can only effect tissue near its path through the animal. A 10" wide path of destruction has a greater terminal effect that a 1" path. Please note we are not advocating using the controlled fracturing feature for a hunter to take marginal shots, we are just exteding the killing performance of a well-placed shot.
Final Penetration/Perforartion
The increased frontal diameter of a mushroomed bullet severly impares additional penetration. The increase surface area slows the bullet down quickly and imperfect mushrooming where one side expands further than the other results in the bullet veering off the inteded course. A large radiused nose also tends to follow the path of least resistance which pulls the bullet off course. If you look at most African game solids, the nose has a large flat which punches through bone and keeps the bullet tracking straight. Once the controlled fractuing of the petals on the Lehigh bullet is complete, the bullet shank continues penetrating with a frontal diameter equal to the bullet diameter. The new nose of the bullet is flat, the best shape for straight line penetration and the cicumference edge around the face is sharp allowing the bullet to cut cleanly and to punch through bone without course variation. The Lehigh bullet shank is designed to retain sufficient energy to completely penetrate the offside hide providing an exit bloodtrail.
In summary, the controlled fracturing of the Lehigh bullet is very different from what we have been conditioned to believe is the optimal performace. The terminal performance of the Lehigh's is devastating and much different than a mushrooming bullet. We are not going to get everyone to drink the Lehigh Koolaide, but I hope over time that people will see through experience that the Lehigh terminal performance is superior. As a bullet designer I have the responsibility to game of creating the most effective bullet possible - this is a responsibility I take very seriously.
Thanks for your inquiry and I hope my explanation was clear.
Dave Fricke
Thankyou for the inquiry on why Lehigh Bullets uses brass instead of copper. I thought I would expand this to also include how the Lehigh bullets function. The design aspects of a good hunting bullet include: accuracy, initial penetration, expansion/energy transfer, organ destruction, and final penetration/perforation.
Accuracy
Accuracy is important for terminal performance as the bullet has to get to the intended location. Lehigh bullets are machined from barstock on cnc lathes. The bullets come off the machine complete with no secondary operations. The bullets are machined at around 8,000 rpm. Due to the bullet being formed while spinning, the concentricity of all the features is inherent in the process. The hollowpoint is centered on the outside diameter and the wall thickness is equal all around the bullet. This means the center of the geometry is equal to the axis of rotation which makes for an accurate bullet. A formed bullet, either a jacketed or formed solid copper bullet is made in a static process, it is not spinning. Manufacturing and tooling tolerances make it very difficult to keep the internal features like the hollowpoint at the true center axis. Most o these bullets are also produced on a press that may form 10-15 at a time. Each of those bullets have the potential for being slightly out of balance due to the different tooling each one sees. I am not stating you can not make an accurate bullet through the forming method; I am just stating it is easier to produce an accurate bullet by machining. The downside of machining bullets is the cycle time. Machining yields somewhere around 120 bullets per hour while forming can yield over 5,000 per hour.
Initial Penetration
The bullet must be stong enough to penetrate the animals hide and muscle boundary before expansion begins. Factors for consideration include the bullet weight, impact velocity, and the animals structure. Due to these variables, bullets have to be designed based on estimated averages which induces performance issues when game is taken at the extremes of where the bullet designers thought the bullet would be used. This effects all manufactures. Machining a bullet from brass enables us to very quickly change the design features like the hollowpoint and then test the result. Since the parameters are controlled by cnc code, it is very simple and fast to change from one design to another enabling the testing of many configurations in a single day to quickly arrive at an optimum design. This process takes much longer on formed bullets as changes are tooling dependent. New dies and punches must be produced for each trial and the equipment must be then setup and centered making it a long process to try to get to the optimum performance level. The investement in tooling is very large and that is why you may find a formed bullet manufacture producing a poorly performing bullet for sometime before changing the design. The tooling and machine may also limit the formed bullet manufacture on how strong they can make the nose for complete initial penetration. The forming machine may not have the power to form a jacket with sufficient wall thickness resulting with a bullet that begins expansion upon contact severly limiting the bullets terminal performance. Machining a brass bullet to any wall thickness is very simple.
Exapnsion/Energy Transfer
This phase of terminal performance is very similar in a Lehigh brass bullet and a copper or jacketed bullet. The process begins as the bullet contacts the animal and completes when the bullet is fully expanded. The nose or metplat, determines the initial energy transfer. Big, flat noses transfer an extreme amount of energy. Depending on the impact point, this energy may be sufficient to shut down the animals nervous system. While a large flat nose is the best design for intital energy transfer, it lowers the ballistic coefficient of the bullet resulting in velocity loss and making it more susceptable to wind conditions.
Upon penetrating the hide and muscle layer, the bullet encounters tissue with a greater liquid content. This hydraulic pressure in the hollopoint cavity causes the nose to expand transfering additional energy to the animal. Expansion is complete when the upset growth stops which on a jacketed bullet could be a partial expansion or when the nose is completely folded back around the shank. Assuming a .500" diameter jacketed bullet, expansion may reach a frontal daimeter of 1.00". Lehigh bullets start expansion much in the same way. The bullets are designed to begin expansion upon the resulting hydraulic pressure. The nose petals are then designed to split the web of material between them. Once the petals achieve an angle of slightly less than 45 degrees, the petals separate from the base and radiate outward on independent trajectory paths. Remember all components of the bullet are still spinning.
Organ Destruction
In this phase there are some very distinct differences between a conventional formed/mushrooming bullet and a Lehigh brass bullet. As the Lehigh bullet's petals radiate outward, additional energy is transferred by each of the six petals. The petals have sharp cutting edges, and coupled with the spinning action, they are devastating to all tissue encountered leading to massive organ damage. The radial pattern will normally extend over 10". A customer recently tested the bullets on a bison and using a metal detector found petals 18" from the base path. Organ destruction was enormous. Often there is sufficient enrgy in the petals to penetrate the offside hide. A convetional mushrooming bullet can only effect tissue near its path through the animal. A 10" wide path of destruction has a greater terminal effect that a 1" path. Please note we are not advocating using the controlled fracturing feature for a hunter to take marginal shots, we are just exteding the killing performance of a well-placed shot.
Final Penetration/Perforartion
The increased frontal diameter of a mushroomed bullet severly impares additional penetration. The increase surface area slows the bullet down quickly and imperfect mushrooming where one side expands further than the other results in the bullet veering off the inteded course. A large radiused nose also tends to follow the path of least resistance which pulls the bullet off course. If you look at most African game solids, the nose has a large flat which punches through bone and keeps the bullet tracking straight. Once the controlled fractuing of the petals on the Lehigh bullet is complete, the bullet shank continues penetrating with a frontal diameter equal to the bullet diameter. The new nose of the bullet is flat, the best shape for straight line penetration and the cicumference edge around the face is sharp allowing the bullet to cut cleanly and to punch through bone without course variation. The Lehigh bullet shank is designed to retain sufficient energy to completely penetrate the offside hide providing an exit bloodtrail.
In summary, the controlled fracturing of the Lehigh bullet is very different from what we have been conditioned to believe is the optimal performace. The terminal performance of the Lehigh's is devastating and much different than a mushrooming bullet. We are not going to get everyone to drink the Lehigh Koolaide, but I hope over time that people will see through experience that the Lehigh terminal performance is superior. As a bullet designer I have the responsibility to game of creating the most effective bullet possible - this is a responsibility I take very seriously.
Thanks for your inquiry and I hope my explanation was clear.
Dave Fricke
