Post by bigblue on Sept 9, 2008 8:34:50 GMT -6
Just some ramblings and food for thought.
Wikipedia-Sectional density is the ratio of an object's weight to its cross-sectional area. It conveys the ability for an object to overcome resistance. When a projectile is in flight or impacting an object, it is the sectional density of that projectile which will determine how efficiently it can overcome the resistance to air or object. The greater the sectional density is for a projectile the greater its efficiency is and therefore ability to overcome the resistance of air and object.
The reason I bring this up is that I was looking at my hunting loads with an eye towards terminal performance. I give my handloads a good workout at the range and know they will hit where I aim, if I do my part, but that isn't always a guaranty that they will perform as well as I'd like. The ability of a bullet to hold together has a lot to do with design, thickness and shape of the jacket, interlocked, interbonded, or solid bullets all hold together differently and the speed of their expansion plays a key role in performance and penetration. Sectional density is based only on the weight and caliber of a bullet and doesn't take into account many of the other characteristics I've mentioned. I'll be taking my 30/06 and 45/70 hunting in a few weeks and I may be hunting elk, fallow deer or whitetails with these rifles. I worked up a load for my 30/06 using a Hornady 180gr. SST bullet with a sectional density of .271 that should work well on the deer, but in the case of the heavier boned elk, I'd limit my shots to double lung and steer clear of any shoulder shots. If the range will be 100 yards or under I'll use my 45/70 with the Cast Performance 460gr. hard cast bullets for the elk simply because I know they will hold together better and that the load will penetrate bone no matter what it hits. By the way the 460gr. 45/70 bullets have a sectional density of .313.
Another factor I look at is the Taylor KO formula, especially when I'm going to hunt larger or possibly dangerous game.
The "Taylor KO formula" was developed by John Taylor. John Talyor was an extremely experienced African hunter, his formula was based on killing thousands of large game animals with nearly any caliber you can imagine. This formula is designed to give you a relative "killing power" number for a given caliber, the higher the number the better.
The Taylor formula takes into account not only the caliber and weight of the bullet, but also the velocity. To give you an example for comparison, the 30/06 shoots that 180gr. bullet at 2750fps resulting in 2967 ft. lbs. of energy and rates a TKO of 21. The 45/70 shoots that 460gr. bullet at 1550fps resulting in 2453 ft. lbs. of energy, but rates a much higher TKO of 46.
In yet another calculator, the Thornily Stopping Power index adds a standard that should give you an idea of what is needed for clean kills on specified game. They do this by assigning an index number for each critter.
45 Antelope
50 Deer
100 Black Bear (To account for 350- 500 lbs. bear.)
120 Elk, Moose, Kudu, Zebra, Large African Safari Plains Game
150 Lion, Leopard, Grizzly Bear, Brown Bear
250 Hippopotamus , Rhinoceros, Cape Buffalo, Elephant
In the case of my 30/06 load, it rates a 110 and my 45/70 load rates a 200. This tells me that the 30/06 should be good for black bear, deer and antelope, but might be marginal for use on elk. Accordingly the 45/70 load should be good for use on anything short of an Hippopotamus , Rhinoceros, Cape Buffalo, or an Elephant.
Here are some links to calculators:
www.handloads.com/calc/quick.asp
www.beartoothbullets.com/rescources/calculators/php/density.htm
www.beartoothbullets.com/rescources/calculators/php/thornily.htm?v1=0&v3=0&v2=0
There are many different index available to use and I only touched on a few. None of these index can be taken as absolute gospel as each animal differs and so do the many various circumstances such as the angle of the shot taken. The thing is that these are factors we can look at prior to taking a shot and will go a long way to help insuring the best possible load.
Don
Wikipedia-Sectional density is the ratio of an object's weight to its cross-sectional area. It conveys the ability for an object to overcome resistance. When a projectile is in flight or impacting an object, it is the sectional density of that projectile which will determine how efficiently it can overcome the resistance to air or object. The greater the sectional density is for a projectile the greater its efficiency is and therefore ability to overcome the resistance of air and object.
The reason I bring this up is that I was looking at my hunting loads with an eye towards terminal performance. I give my handloads a good workout at the range and know they will hit where I aim, if I do my part, but that isn't always a guaranty that they will perform as well as I'd like. The ability of a bullet to hold together has a lot to do with design, thickness and shape of the jacket, interlocked, interbonded, or solid bullets all hold together differently and the speed of their expansion plays a key role in performance and penetration. Sectional density is based only on the weight and caliber of a bullet and doesn't take into account many of the other characteristics I've mentioned. I'll be taking my 30/06 and 45/70 hunting in a few weeks and I may be hunting elk, fallow deer or whitetails with these rifles. I worked up a load for my 30/06 using a Hornady 180gr. SST bullet with a sectional density of .271 that should work well on the deer, but in the case of the heavier boned elk, I'd limit my shots to double lung and steer clear of any shoulder shots. If the range will be 100 yards or under I'll use my 45/70 with the Cast Performance 460gr. hard cast bullets for the elk simply because I know they will hold together better and that the load will penetrate bone no matter what it hits. By the way the 460gr. 45/70 bullets have a sectional density of .313.
Another factor I look at is the Taylor KO formula, especially when I'm going to hunt larger or possibly dangerous game.
The "Taylor KO formula" was developed by John Taylor. John Talyor was an extremely experienced African hunter, his formula was based on killing thousands of large game animals with nearly any caliber you can imagine. This formula is designed to give you a relative "killing power" number for a given caliber, the higher the number the better.
The Taylor formula takes into account not only the caliber and weight of the bullet, but also the velocity. To give you an example for comparison, the 30/06 shoots that 180gr. bullet at 2750fps resulting in 2967 ft. lbs. of energy and rates a TKO of 21. The 45/70 shoots that 460gr. bullet at 1550fps resulting in 2453 ft. lbs. of energy, but rates a much higher TKO of 46.
In yet another calculator, the Thornily Stopping Power index adds a standard that should give you an idea of what is needed for clean kills on specified game. They do this by assigning an index number for each critter.
45 Antelope
50 Deer
100 Black Bear (To account for 350- 500 lbs. bear.)
120 Elk, Moose, Kudu, Zebra, Large African Safari Plains Game
150 Lion, Leopard, Grizzly Bear, Brown Bear
250 Hippopotamus , Rhinoceros, Cape Buffalo, Elephant
In the case of my 30/06 load, it rates a 110 and my 45/70 load rates a 200. This tells me that the 30/06 should be good for black bear, deer and antelope, but might be marginal for use on elk. Accordingly the 45/70 load should be good for use on anything short of an Hippopotamus , Rhinoceros, Cape Buffalo, or an Elephant.
Here are some links to calculators:
www.handloads.com/calc/quick.asp
www.beartoothbullets.com/rescources/calculators/php/density.htm
www.beartoothbullets.com/rescources/calculators/php/thornily.htm?v1=0&v3=0&v2=0
There are many different index available to use and I only touched on a few. None of these index can be taken as absolute gospel as each animal differs and so do the many various circumstances such as the angle of the shot taken. The thing is that these are factors we can look at prior to taking a shot and will go a long way to help insuring the best possible load.
Don