Dangerously high PF

[LuckyDucky]

A desert eagle in 50AE is over 400 PF and a .500 S&W is over 600 PF

[kneelingatlas]

As a reloader I think it's important to know the difference between power factor and kinetic energy; PF is a simple momentum formula which I believe (someone who knows better please step in) began as a pendulum test with the idea that rounds with the same PF would have the same probability of knocking down the same piece of steel.

I suspect the factors which effect the longevity of a pistol and the impulse of the recoil have more to do with energy. If you play around with this calculator (http://www.tresterscustomguns.com/calcnrg.html) you'll see that holding PF constant, the lighter bullets at higher velocities have drastically more kinetic energy (which makes sense since velocity is squared in the energy formula). This is in keeping with the idea that heavier bullets at the same PF produce a softer recoil.

Look at a 115gr bullet traveling 1450fps and a 230gr bullet traveling 725fps; both have a PF of 166.75, but the 9mm has double the energy of the .45 (536.76 vs 268.38) so without a compensator to dissipate some of that energy, the recoil impulse of the 9mm would be punishing (this is why I always advise against shooting 9 Major without a comp) on the shooter's arms as well as the pistol.

If someone really wanted to shoot 9 Major without a comp they could shoot 160gr pills at 1042fps and cut the energy down to 386.

Edited July 14, 2014 by kneelingatlas

[56hawk]

Highest power factor ammo I have shot in a match was 425. But, as others have mentioned the actual load is what is important. Figuring a 9x23 is rated for 55,000 psi and hopefully you are shooting 38 Super out of a similar strength gun that should give you a much better idea of what is safe. Honestly I don't think you could force enough N105 into a Super case to get the pressure anywhere near 55,000 psi.

[peterthefish]

As a reloader I think it's important to know the difference between power factor and kinetic energy; PF is a simple momentum formula which I believe (someone who knows better please step in) began as a pendulum test with the idea that rounds with the same PF would have the same probability of knocking down the same piece of steel.

I suspect the factors which effect the longevity of a pistol and the impulse of the recoil have more to do with energy. If you play around with this calculator (http://www.tresterscustomguns.com/calcnrg.html) you'll see that holding PF constant, the lighter bullets at higher velocities have drastically more kinetic energy (which makes sense since velocity is squared in the energy formula). This is in keeping with the idea that heavier bullets at the same PF produce a softer recoil.

Look at a 115gr bullet traveling 1450fps and a 230gr bullet traveling 725fps; both have a PF of 166.75, but the 9mm has double the energy of the .45 (536.76 vs 268.38) so without a compensator to dissipate some of that energy, the recoil impulse of the 9mm would be punishing (this is why I always advise against shooting 9 Major without a comp) on the shooter's arms as well as the pistol.

If someone really wanted to shoot 9 Major without a comp they could shoot 160gr pills at 1042fps and cut the energy down to 386.

You are on the right track but a bit off on the reasonably. Then a gun is fired, momentum is conserved. That is, the momentum of the ejecta (Mass X Velocity) = the momentum of the recoiling firearm, regardless of the kinetic energy of the projectile. However, it takes more energy (i.e. More powder) to move the lighter projectile faster (i.e. produce higher K.E.). The gases produced by that additional powder have increased mass over the gas produced by a lighter powder charge. Moreover, those gases are moving faster than the projectile, resulting in greater momentum of the ejecta and thus greater momentum of the recoiling firearm.

Here's an example ; Imagine 5 grains of Powder A Moves a 230 GR projectile at 850 FPS; while 10 Grains of Powder B (a slower powder) does the same. Lets assume that exit gases move at 1500 FPS.

For powder A, recoil momentum = (850 x 230) + (5 x 1500) =203,000. For Powder B, recoil momentum = (850 X 230) + (10 x 1500) = 210,500, which is about a 3.7% increase.

In theory, doubling KE (while maintaining constant momentum / PF) requires doubling input energy - that is, the powder charge. In reality, you have to more then double the charge as higher velocity means more energy lost to heat, sounds, etc...

[Front Man]

Agreed Bill!

[SilverBolt]

If I remember right the high PF at Area-1 this year was 210. No idea what caliber.

[kneelingatlas]

If I remember right the high PF at Area-1 this year was 210. No idea what caliber.

I would guess factory .45 ammo.

[MangledMoose]

If I remember right the high PF at Area-1 this year was 210. No idea what caliber.

208