I was just on Hodgdon's website looking at the reloading data for the 25-06 and the 257 Roberts. Using H4350 and a 75gr V-Max, the .257 achieves 3422fps with 50gr of powder while the 25-06 gets 3460 with 54gr of powder. 4gr of powder for 38fps doesn't seem right for some reason. The 25-06 is at 43,300 CUP while the 257 is at 44,000 CUP.
This doesn't make sense to me
- Thread starter KDX
- Start date
If you look at other cartridges in the manual and compare case capacity to bullet weight you will see a lot of similarities.
Where the larger cases really shine, is when heavy bullets are required or used.
Another good example of this is the 308Win and the 30-06Springfield. With light bullets, the 308Win will do every bit as well as the 30-06. Go to a 180+ grain bullet and the 30-06 soon starts to exceed the velocities that can be achieved with the smaller case. That is the real advantage to magnum cases as well.
When it comes to powder capacities vs bullet weights, the laws of diminishing returns soon come into play as the projectiles get lighter.
In your case, the 75 grain pills are on the light side of bullets available for both cartridges.
Where the larger cases really shine, is when heavy bullets are required or used.
Another good example of this is the 308Win and the 30-06Springfield. With light bullets, the 308Win will do every bit as well as the 30-06. Go to a 180+ grain bullet and the 30-06 soon starts to exceed the velocities that can be achieved with the smaller case. That is the real advantage to magnum cases as well.
When it comes to powder capacities vs bullet weights, the laws of diminishing returns soon come into play as the projectiles get lighter.
In your case, the 75 grain pills are on the light side of bullets available for both cartridges.
Better 257 Roberts expansion ratio explains it!
Expansion ratio explains it all:
257 Roberts has a much greater expansion ratio than a 25-06 in both cartridges are fired from a 24" barrel.
The basic principle is that mechanical work is done by propellant gas expanding and push the bullet. The more the propellant expand (the longer the piston stroke), the more efficient is the energy transfer from gas pressure to bullet kinetic energy.
This ratio determines how much of the chemical energy in the propellant is transformed into kinetic energy.
This is somewhat dry reading but very well explained for various .30 cartridges.
http://www.z-hat.com/Efficiency%20of%20the%20300%20Hawk.htm
After reading this you'll finally understand why 308 in a 24" barrel is more efficient than a 30-06 in a 24" barrel and 300 Win Mag in a 24" barrel is by far the worse.
The most interesting graph is Figure 5 where the energy transformed and lost is show for different cartridge for a 24" barrel.
Alex
Expansion ratio explains it all:
257 Roberts has a much greater expansion ratio than a 25-06 in both cartridges are fired from a 24" barrel.
The basic principle is that mechanical work is done by propellant gas expanding and push the bullet. The more the propellant expand (the longer the piston stroke), the more efficient is the energy transfer from gas pressure to bullet kinetic energy.
This ratio determines how much of the chemical energy in the propellant is transformed into kinetic energy.
This is somewhat dry reading but very well explained for various .30 cartridges.
http://www.z-hat.com/Efficiency%20of%20the%20300%20Hawk.htm
After reading this you'll finally understand why 308 in a 24" barrel is more efficient than a 30-06 in a 24" barrel and 300 Win Mag in a 24" barrel is by far the worse.
The most interesting graph is Figure 5 where the energy transformed and lost is show for different cartridge for a 24" barrel.
Alex
