Hello,
I’ve been seeing a reoccurring theme in questions that relate around the world of ballistics both with my customers, students, and within the questions posed to Randy on his Elk Talk series so I thought I would share some of my knowledge and experience so that others may learn how to figure this question out for themselves to make better informed decisions for themselves. No one knows your environment, style, abilities, and wants better than you so it only makes sense to empower you with knowledge so that you may be better effective in the field. This topic can get quite lengthy but there is a lot of information to convey in order to teach and give tools required to make informed decisions with.
First let me start off by saying a bit about myself, I am a gunsmith, engineer and machinist, I have been doing this off and on since I was very young, taking a break from the profession while serving our country. I obtained my Bachelors of Science in IT, and later an MBA but I couldn’t leave my passion of shooting, hunting, and gunsmithing. I do this all day every day, shoot competitively and my shooting passion is extreme ultra long range shooting (I’ve personally shot groups beyond 4000 yards). This discussion is not intended to discuss the ethics, morals and skillsets of long range hunting, rather a brief overview of external ballistics that directly tie into terminal performance. I shoot a lot, upwards of 800-1200 rounds of precision fire a week and I’m ever learning myself so please don’t take my opinions and experiences as the end all but rather a guidance to a direction to find the information you need for yourself and your situation.
The initial question I get personally and that I’ve seen asked to Randy on Elk Talk is something like “Is XXX cartridge enough to kill an elk?”. I thought Randy did a good job in responding with “well it depends” because, well, it does depend on a huge amount of variables. We all know shot placement determines almost everything when it comes to hunting, so for now we’ll make some assumptions in order to carry on a discussion, a well-placed shot center mass of the vitals on an elk. With this assumption we need parameters to gauge what is and what is not “enough power” to reliably cause enough penetration and tissue damage to take an animal. Many states list minimum requirements with what is a legal firearm to hunt elk with, usually a combination of minimum caliber (typically 6mm/243) and even go as far as to list minimum energy requirements either at the muzzle or at a given impact distance. Colorado states: “Rifles using center-fire cartridges of .24 caliber or larger, having expanding bullets of at least seventy (70) grains in weight, except for elk and moose where the minimum bullet weight is eighty-five (85) grains, and with a rated impact energy one hundred (100) yards from the muzzle of at least one thousand (1000) foot pounds as determined by the manufacturer's rating…”, (Colorado Parks & Wildlife Regulations- Big Game, 2017). Having this parameter set gives us a minimum of a go/no go situation while finding the answers to the question; What is enough bullet?
External ballistics is the term used to describe what a projectile does between the time it exits the muzzle it impacts its target (or stops its flight). This is in an exercise of physics in order to determine what bullet does what and when, yes the main function of ballistics is the driver behind precision rifle fire, adjustments for distance and CDS dials etc.… but for this purpose we will focusing on the energy potential to find out “what is enough bullet”. We know from the regulations that we need a bullet of at least .243 caliber and weight of 85 grains, we also know that we need at least an impact energy of 1000 foot pounds (ftLbs) at 100 yards. Again, some assumptions need to be made. This assumption is that the generally excepted hunting distance is around 100 yards so for discussion purposes we will substitute the term that we need 1000 ftlbs of energy at point of impact.
We would not be doing our due diligence if we only ran the ballistics based upon impact energy alone, velocity is a key function of energy in ballistics. In a basic sense, mass*velocity=energy. However not all bullets are created equal nor created to do the same job in the same manner. So again research is required to find out what our parameters are in order to create a go/no go situation. In order to stop a discussion about which brand is better than another I’ll use a made-up projectile. The manufacture of the projectile states that maximum and minimum effective expansion range of the bullet is between 2800 feet per second (fps) and 1800 fps. For right now we’re focused on the lower end of those numbers but the higher end will be discussed later.
So now we have our minimum parameters of 1800 fps and 1000 ftlbs of energy at point of impact. Rather than actually lay out the math to do it the long way, there’s a huge amount of tools available online for free as well as some very advanced tools to purchase. Personally I use Applied Ballistics (both at home doing desk testing and in the field) and a beta test version sent to me by another well-known ballistics researcher. Berger Bullets, Applied Ballistics, Hornady, and many others have great, free, and simple to use ballistic solvers online. The results given for this purpose of “what’s enough bullet?” are theoretical max effective range, just because it says you can shoot that far doesn’t mean you should or will, this is just an FYI purpose to help you make decisions on what is enough.
The direct impact on a projectiles ability to maintain speed and energy is the projectiles Ballistic Coefficient (BC). There are multiple different types of BC out there, most common are the G1 and the G7 ballistic drag profile. They are not the same and have different purposes, USUALLY the G7 profile most accurately represents modern bullet designs however the shooting industry has adopted the G1 long ago and that’s what most users are familiar with, however I recommend the use of the G7 profile if available and applicable for your projectile choice. Another semi-major note is not all manufactures measure their G1/G7’s in the same manor in the same conditions, there is no real “standard” for this and do not trust the numbers provided by the manufacture until you’ve verified them yourself in your platform. Rifle twist rates have a major impact on the BC’s, just because shooter “A” and shooter “B” shoot the same projectile but they have twist rates different from each can have major or minor change in BC of the projectile. Unfortunately, factory rifles tend to be on the slow side (both in terms of twist rates and keeping up with the trends in modern projectile development). Just because a rifle groups a bullet well does not mean it’s actually giving that projectile enough stability to gain all of the ballistic potential advantage that projectile has. Berger Bullets has a free online bullet stability factor calculator for you input your setup and see if you’re reaching the potential or somewhere below the potential (idea stability factor numbers are above 1.5).
The next major piece of information needed is the starting speed of the bullet, typically referred to as the muzzle velocity. If possible, always, ALWAYS, I’ll say it again, ALWAYS verify your muzzle velocity either with a good chronograph or through ballistic solver calibration, or ideally both. If you do not have access to these tools you can use the manufactures information as a baseline starting point for initial data collection and results to answer the foundation question. You want the best, most accurate or most representative data you can get, remember with all math and physics solving, trash in = trash out. Now that you have some data to start with, there’s one more piece of the puzzle that has a major impact and is a form of reality with elk hunting, environmental conditions. I’m sure most have heard people discuss how temperature, humidity, elevation effect ballistics, they do, A LOT. However to break it down simply, the environmental conditions are used to compute what the density of the air the projectile is traveling through is. The less dense the air, the less the projectile is shedding velocity and energy. It’s my experience that the ground elevation, temperature, and air pressure (station or Baro) have the most effect on the density of the bullet, yes humidity does have an effect but it’s my opinion that the humidity amount is the least important aspect of the environmental conditions. So now we have a brief idea of what information is needed to get to our desired outcome information, we can get to the meats and potatoes of the initial question, what’s enough?
I’ve been seeing a reoccurring theme in questions that relate around the world of ballistics both with my customers, students, and within the questions posed to Randy on his Elk Talk series so I thought I would share some of my knowledge and experience so that others may learn how to figure this question out for themselves to make better informed decisions for themselves. No one knows your environment, style, abilities, and wants better than you so it only makes sense to empower you with knowledge so that you may be better effective in the field. This topic can get quite lengthy but there is a lot of information to convey in order to teach and give tools required to make informed decisions with.
First let me start off by saying a bit about myself, I am a gunsmith, engineer and machinist, I have been doing this off and on since I was very young, taking a break from the profession while serving our country. I obtained my Bachelors of Science in IT, and later an MBA but I couldn’t leave my passion of shooting, hunting, and gunsmithing. I do this all day every day, shoot competitively and my shooting passion is extreme ultra long range shooting (I’ve personally shot groups beyond 4000 yards). This discussion is not intended to discuss the ethics, morals and skillsets of long range hunting, rather a brief overview of external ballistics that directly tie into terminal performance. I shoot a lot, upwards of 800-1200 rounds of precision fire a week and I’m ever learning myself so please don’t take my opinions and experiences as the end all but rather a guidance to a direction to find the information you need for yourself and your situation.
The initial question I get personally and that I’ve seen asked to Randy on Elk Talk is something like “Is XXX cartridge enough to kill an elk?”. I thought Randy did a good job in responding with “well it depends” because, well, it does depend on a huge amount of variables. We all know shot placement determines almost everything when it comes to hunting, so for now we’ll make some assumptions in order to carry on a discussion, a well-placed shot center mass of the vitals on an elk. With this assumption we need parameters to gauge what is and what is not “enough power” to reliably cause enough penetration and tissue damage to take an animal. Many states list minimum requirements with what is a legal firearm to hunt elk with, usually a combination of minimum caliber (typically 6mm/243) and even go as far as to list minimum energy requirements either at the muzzle or at a given impact distance. Colorado states: “Rifles using center-fire cartridges of .24 caliber or larger, having expanding bullets of at least seventy (70) grains in weight, except for elk and moose where the minimum bullet weight is eighty-five (85) grains, and with a rated impact energy one hundred (100) yards from the muzzle of at least one thousand (1000) foot pounds as determined by the manufacturer's rating…”, (Colorado Parks & Wildlife Regulations- Big Game, 2017). Having this parameter set gives us a minimum of a go/no go situation while finding the answers to the question; What is enough bullet?
External ballistics is the term used to describe what a projectile does between the time it exits the muzzle it impacts its target (or stops its flight). This is in an exercise of physics in order to determine what bullet does what and when, yes the main function of ballistics is the driver behind precision rifle fire, adjustments for distance and CDS dials etc.… but for this purpose we will focusing on the energy potential to find out “what is enough bullet”. We know from the regulations that we need a bullet of at least .243 caliber and weight of 85 grains, we also know that we need at least an impact energy of 1000 foot pounds (ftLbs) at 100 yards. Again, some assumptions need to be made. This assumption is that the generally excepted hunting distance is around 100 yards so for discussion purposes we will substitute the term that we need 1000 ftlbs of energy at point of impact.
We would not be doing our due diligence if we only ran the ballistics based upon impact energy alone, velocity is a key function of energy in ballistics. In a basic sense, mass*velocity=energy. However not all bullets are created equal nor created to do the same job in the same manner. So again research is required to find out what our parameters are in order to create a go/no go situation. In order to stop a discussion about which brand is better than another I’ll use a made-up projectile. The manufacture of the projectile states that maximum and minimum effective expansion range of the bullet is between 2800 feet per second (fps) and 1800 fps. For right now we’re focused on the lower end of those numbers but the higher end will be discussed later.
So now we have our minimum parameters of 1800 fps and 1000 ftlbs of energy at point of impact. Rather than actually lay out the math to do it the long way, there’s a huge amount of tools available online for free as well as some very advanced tools to purchase. Personally I use Applied Ballistics (both at home doing desk testing and in the field) and a beta test version sent to me by another well-known ballistics researcher. Berger Bullets, Applied Ballistics, Hornady, and many others have great, free, and simple to use ballistic solvers online. The results given for this purpose of “what’s enough bullet?” are theoretical max effective range, just because it says you can shoot that far doesn’t mean you should or will, this is just an FYI purpose to help you make decisions on what is enough.
The direct impact on a projectiles ability to maintain speed and energy is the projectiles Ballistic Coefficient (BC). There are multiple different types of BC out there, most common are the G1 and the G7 ballistic drag profile. They are not the same and have different purposes, USUALLY the G7 profile most accurately represents modern bullet designs however the shooting industry has adopted the G1 long ago and that’s what most users are familiar with, however I recommend the use of the G7 profile if available and applicable for your projectile choice. Another semi-major note is not all manufactures measure their G1/G7’s in the same manor in the same conditions, there is no real “standard” for this and do not trust the numbers provided by the manufacture until you’ve verified them yourself in your platform. Rifle twist rates have a major impact on the BC’s, just because shooter “A” and shooter “B” shoot the same projectile but they have twist rates different from each can have major or minor change in BC of the projectile. Unfortunately, factory rifles tend to be on the slow side (both in terms of twist rates and keeping up with the trends in modern projectile development). Just because a rifle groups a bullet well does not mean it’s actually giving that projectile enough stability to gain all of the ballistic potential advantage that projectile has. Berger Bullets has a free online bullet stability factor calculator for you input your setup and see if you’re reaching the potential or somewhere below the potential (idea stability factor numbers are above 1.5).
The next major piece of information needed is the starting speed of the bullet, typically referred to as the muzzle velocity. If possible, always, ALWAYS, I’ll say it again, ALWAYS verify your muzzle velocity either with a good chronograph or through ballistic solver calibration, or ideally both. If you do not have access to these tools you can use the manufactures information as a baseline starting point for initial data collection and results to answer the foundation question. You want the best, most accurate or most representative data you can get, remember with all math and physics solving, trash in = trash out. Now that you have some data to start with, there’s one more piece of the puzzle that has a major impact and is a form of reality with elk hunting, environmental conditions. I’m sure most have heard people discuss how temperature, humidity, elevation effect ballistics, they do, A LOT. However to break it down simply, the environmental conditions are used to compute what the density of the air the projectile is traveling through is. The less dense the air, the less the projectile is shedding velocity and energy. It’s my experience that the ground elevation, temperature, and air pressure (station or Baro) have the most effect on the density of the bullet, yes humidity does have an effect but it’s my opinion that the humidity amount is the least important aspect of the environmental conditions. So now we have a brief idea of what information is needed to get to our desired outcome information, we can get to the meats and potatoes of the initial question, what’s enough?
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