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.

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