+P questions...

Hunt200 · #1 03-18-2009, 04:19 AM

OK, I know this has been beat to death, but...............

What makes a round a +P? I know it stands for plus pressure, but when looking at the rounds below, which are just a sample I pulled from the web, I don't understand why some of these are +P and some not. I know the weight of the bullet is a factor, but wouldn't the velocity and energy determine if it should be rated +P? Can someone please enlighten me.

Federal Premium Personal Defense Low Recoil Ammunition 38 Special 110 Grain Hydra-Shok Jacketed Hollow Point
Muzzle Velocity: 1000 fps
Muzzle Energy: 244 ft. lbs.

Federal Premium Personal Defense Ammunition 38 Special +P 129 Grain Hydra-Shok Jacketed Hollow Point
Muzzle Velocity: 950 fps
Muzzle Energy: 258 ft. lbs.

Hornady Custom Ammunition 38 Special 125 Grain XTP Jacketed Hollow Point Box of 25
Muzzle Velocity: 900 fps
Muzzle Energy: 225 ft/lb

Remington Golden Saber Ammunition 38 Special +P 125 Grain Brass Jacketed Hollow Point
Muzzle velocity: 975 fps
Muzzle energy: 264 ft/lb

Speer Gold Dot Ammunition 38 Special +P 125 Grain Jacketed Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 248 ft/lb

Speer Gold Dot Short Barrel Ammunition 38 Special +P 135 Grain Jacketed Hollow Point
Muzzle Velocity: 860 fps
Muzzle Energy: 222 ft. lbs.

Winchester Super-X Ammunition 38 Special 110 Grain Silvertip Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 218 ft. lbs.

Winchester USA Ammunition 38 Special +P 125 Grain Jacketed Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 248 ft. lbs.

Winchester Super-X Ammunition 38 Special +P 158 Grain Lead Hollow Point Semi-Wadcutter
Muzzle Velocity: 890 fps
Muzzle Energy: 278 ft. lbs.

Grizzly Ammunition 38 Special 158 Grain Wide Flat Nose Plane Base
Muzzle Velocity: 950 fps
Muzzle Energy: 315 ft. lbs.

Hunt200 · #2 03-18-2009, 04:19 AM

OK, I know this has been beat to death, but...............

What makes a round a +P? I know it stands for plus pressure, but when looking at the rounds below, which are just a sample I pulled from the web, I don't understand why some of these are +P and some not. I know the weight of the bullet is a factor, but wouldn't the velocity and energy determine if it should be rated +P? Can someone please enlighten me.

Federal Premium Personal Defense Low Recoil Ammunition 38 Special 110 Grain Hydra-Shok Jacketed Hollow Point
Muzzle Velocity: 1000 fps
Muzzle Energy: 244 ft. lbs.

Federal Premium Personal Defense Ammunition 38 Special +P 129 Grain Hydra-Shok Jacketed Hollow Point
Muzzle Velocity: 950 fps
Muzzle Energy: 258 ft. lbs.

Hornady Custom Ammunition 38 Special 125 Grain XTP Jacketed Hollow Point Box of 25
Muzzle Velocity: 900 fps
Muzzle Energy: 225 ft/lb

Remington Golden Saber Ammunition 38 Special +P 125 Grain Brass Jacketed Hollow Point
Muzzle velocity: 975 fps
Muzzle energy: 264 ft/lb

Speer Gold Dot Ammunition 38 Special +P 125 Grain Jacketed Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 248 ft/lb

Speer Gold Dot Short Barrel Ammunition 38 Special +P 135 Grain Jacketed Hollow Point
Muzzle Velocity: 860 fps
Muzzle Energy: 222 ft. lbs.

Winchester Super-X Ammunition 38 Special 110 Grain Silvertip Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 218 ft. lbs.

Winchester USA Ammunition 38 Special +P 125 Grain Jacketed Hollow Point
Muzzle Velocity: 945 fps
Muzzle Energy: 248 ft. lbs.

Winchester Super-X Ammunition 38 Special +P 158 Grain Lead Hollow Point Semi-Wadcutter
Muzzle Velocity: 890 fps
Muzzle Energy: 278 ft. lbs.

Grizzly Ammunition 38 Special 158 Grain Wide Flat Nose Plane Base
Muzzle Velocity: 950 fps
Muzzle Energy: 315 ft. lbs.

Erich · #3 03-18-2009, 04:39 AM

You've got it, it's all about the pressure. (I believe SAAMI set the +P specs as over 18,500 CUP - read more here to be sure: http://www.saami.org/index.cfm .) Internal pressures vary with the components used. Higher internal pressure does not necessarily translate into better external ballistics.

Hunt200 · #4 03-18-2009, 05:33 AM

Thanks for the link Erich, so basically you can't tell what the pressure is by the projectile weight, velocity and energy. The velocity and energy will be effected by the pressure created.

To really know if it considered +P You would need to know what the loader loaded the pressure to?

But why does some non +P ammo have greater velocity and energy than a +P yet it is rated not +P? Wouldn't you except the higher velocity and energy to be a direct correlation to the pressure?

PRESSURE
In a gun or cartridge, the force imparted to various components that is developed by the expanding gases generated by the deflagration of the propellant when fired.
MUZZLE ENERGY
A projectile’s energy at the time it leaves the muzzle of a gun.
MUZZLE VELOCITY
The velocity of a projectile as it exits the muzzle of a firearm.
CRUSHER
A metallic cylinder which, when used in conjunction with a piston and associated equipment, can be used to measure cartridge pressures. Deformation is correlated with peak pressure.
CUP (COPPER UNIT OF PRESSURE)
A pressure value determined by means of copper crusher cylinders using SAAMI recommended procedures and equipment.

Erich · #5 03-18-2009, 06:25 AM

Dom, you can't expect all things to be equal internally when different components are used.

For instance, I can get a 158-grain .357 bullet going 900 fps from a 3" barrel with either Unique or Bullseye. It'll take different weights of each of those powders to get it there. And, since the burn rates of the powders are different, the internal pressures will be different. (This would be safe to do with Unique within .38 +P SAAMI specs, but not with the faster-burning Bullseye.)

If you have an interest in internal ballistics and burn rates, you might pick up a couple of reloading manuals and read up on the subject.

Hunt200 · #6 03-18-2009, 06:40 AM

Thanks, I do believe I have the jist of it now!!

walkinghorse · #7 03-18-2009, 07:11 AM

Erich has very succiently explained it!

Pressure is one reason why there are so many different powders out there, and why some loads give a desired result,say velocity, but also an undesired result, say wear or damage to the firearm.

Just starting to learn about when pressure peaks and duration occur, and the subsequent affect that can have, which Erich and others have broached before!

OKFC05 · #8 03-19-2009, 01:49 PM

A (Very) Short Course in Internal Ballistics

Internal ballistics, or the science of what goes on inside of the gun, is a very complicated topic. This link is not designed to give you a degree in the field but rather to provide some background data to help you understand the subject.

http://www.frfrogspad.com/intballi.htm