Just thought I would add my 2 cents here.

I don't see how peak pressure by itself could have any effect on recoil energy. At the time it occurs, the forces inside the barrel are contained in a closed system. The recoil does not occur until the bullet exits the barrel. The formula I have seen for calculating recoil energy takes into account the weight of the bullet, velocity of the bullet, weight of the escaping gases (assumed to be equal to the powder charge weight), and the velocity of those escaping gases.

The velocity of the escaping gases will vary with the magnitude of the remaining pressure in the barrel at the moment the bullet exits. If this pressure is higher, the velocity of the gases will be greater. The opposite would also be true. The increasing or decreasing velocity of the escaping gases will have a like effect on the recoil energy.

Taken in this context, pressure does effect recoil energy. But only the remaining pressure at the moment the bullet exits. From observing the pressure curve in Quickload and given the same peak pressure in the same cartridge with the same bullet and barrel length, I have noticed that in addition to faster burning powders have a faster pressure rise and fall time, they tend to have lower pressure at bullet exit than slower burning powders. Thus, lower gas exit velocity than with slower powders.

>The recoil does not occur until the bullet exits the barrel.<

Why would you think that? The rifle starts to recoil the instant the bullet starts to move.

tbob38
Technically you are correct, but the recoil movement as a result of the acceleration and travel of the bullet to the muzzle is very small. As reported by Harold Vaughan in Rifle Accuracy Facts:

"....a rifle barrel and action, not connected to the stock, will recoil about 0.10" during the time the bullet is in the barrel."

Add the weight of a stock and the shooter behind it, and that 0.10" probably becomes even less. The rifle Vaughan used for these tests was a Remington 721 in cal 270 Win.

As soon as the bullet leaves the muzzle, the gas venting from the muzzle turns the rifle into a rocket motor that tries to fly backwards, and that is when you experience the major portion of the felt recoil.

Gerard. While it is true that the rifle has not moved very far by the time the bullet has left the barrel, it has gained all of the velocity that it will get due to the acceleration of the bullet and part of the mass of the gas. Consider that the bullet has only moved a little over 20 inches by that time too. The rifle will be accelerated again due to the reaction of the gas leaving the muzzle, and it will gain still more velocity, unless it is attached to or shis something something very solid.

Ok, now after all this, in a nutshell and from personal experience- will a smaller powder charge in my 300 win mag likely result in less recoil?

for instance:
300 win mag 180 grain bullet

60 grains of IMR4320 78% load density 2950fps

vs.

73.5 grains of WMR 95% load density 2950fps

Is it safe to guess the 60 grain load will kick less, or do i need to know the pressures involved to come to a conclusion (other then just shooting them both)?

Now its time to get back to the engineering homework, thank god its only structures! Physics and Fluid mechanics weren't my stongest classes, ill leave this theory stuff to you guys!
sean

[ 01-21-2003, 12:35: Message edited by: SeanD ]

SeanD, The 73.5 load is going to give you more felt recoil. The actual difference however might not be able to be felt to the shooter. Simple, you've burned more energy in this particular case.

ksduckhunter, your wrong in that the gas velocity in the barrel/chamber is the same velocity as the bullet. Take up photography and open your eyes for they say a picture is worth a thousand words.

Anyway, the pressure has not yet had enough time to effect its full power exchange to propel the projectile to the velocity of escaping gasses. This is mostly true on shorter barreled firearms which gives the projectile even less time for the energy exchange, or to completely burn the powder charge which often occures.

Also you mentioned of blow by that occures. Well, if the pressure of the gasses is the same of the bullet's velocity, then why would the pressure be passing up the bullet if the velocities of both were the same ? Bad projectile seal huh ! So there's another variable factor in felt recoil, and in all cases your reality isn't always predictable in individual cases.

You also wrote, "There is no additional "push" by the gas as it escapes with the bullet." I never meant that once the bullet exits the muzzle, the pressure all of a sudden puffs out harder and gives it one more big shove. What I meant was : that once the gases escape out of the end of the barrel, it aids in pushing the rifle rearward in a "jet effect" (turn on a powerful hose and watch part of the end flip around for the pressure/force of the escaping water effect "jet effect" on the hose.

your done, no you'll be back.... this stuff's addicting.......

Dennis