Please explain +P ammo

[Braggs]

Hello OSA members,

I have a question regarding +P ammo. I thought that the # of grains listed on the box indicated both the number of gunpowder grains used as well as the rating for the bullet. How can a 115 grain 9mm cartridge be +P? Wouldn't they have to say it's 125 grain or something? Did they compress the 115 grains into a smaller space in the cartridge? Can someone please explain this for me.

Here's a photo from someone's classified post for evidence:

[Broken External Image]

Thanks for the responses!

Braggs

 

[Old Fart]

Short answer:
More powder more power.

 

[ttown]

The 115 gr. is the bullet weight not the power in the round.

 

[NikatKimber]

You were incorrect in your thinking on what the grains refer to. That is ONLY the weight of the bullet. The bullet weighs 115 grains. They do not advertise how much, or what kind of, powder they use. +P refers to a higher acceptable pressure limit.

 

[jtischauser]

anybody ever chrono any 9mm +P+ through a Glock 17 by chance?

 

[LightningCrash]

anybody ever chrono any 9mm +P+ through a Glock 17 by chance?

http://www.glocktalk.com/forums/showthread.php?t=1171455&page=2
post #49

 

[Rod Snell]

Braggs, here's the deal on the pressure ratings.
SAAMI is the shooting organization that "keeps the books" on the various standards and practices of the industry in the US.
For each cartridge, there is a standard size and pressure. For some cartridges, there is a +P pressure rating that is more than the cartridge standard. However, not all +P are created equal. A +P .38 Spl is much lower in pressure than a +P 9mm Luger. A 7mm rifle cartridge is higher pressure than either.
7mm-08 61,000 38 S&W 14,500

9mm Luger 35,000
7mm BR 52,000 cup 9mm Luger +P 38,500

70-30 Waters 45,000 38 Special 17,000
7.62x39 45,000 38 Special +P 20,000
8mm Mauser 35,000 38 Super +P 36,500
8mm Rem Magnum 65,000 357 Magnum 35,000
22-250 Remington 65,000 357 Maximum 40,000
222 Remington 50,000 40 S&W 35,000
Pressure in PSI.
http://www.handloads.com/misc/saami.htm

You will hear about +P+, which is often misunderstood.
There are no SAAMI standards for +P+, and the manufacturer loads it to whatever they choose. Some are a little over +P; some foreign +P+ is way over and dangerous to shoot in a handgun.

As to how many grains of powder are in a factory cartridge, there is no way to know because they use different powders and have extensive labs to make sure they meet SAAMI pressure standards.
The number printed on the box is the weight of the bullet.

 

[HiredHand]

Some older cartridges would have indicated the projectile diameter and the grains of powder. So, a 45-70 Government would be have been a 45 cal projectile and 70 grains of blackpowder.

 

[Braggs]

Great answers everyone.

Lets make sure I understand this correctly... the grains printed on the box is the weight of the bullet, not the amount of powder the bullet is rated for.

Nobody prints how much or what kind of powder they use.

+P means more powder than normal (maybe they pack it in tighter creating more pressure in the casing?)

+P+ is even more powder than that.

So, for reloading purposes, how do you know how much powder to put in the brass? Do you start with half the bullet weight just for plinking (less $$)? Will a bullet that's 115 grain destabilize (meaning to breakup or disintegrate) if one uses too much powder behind it?

Thanks,

Braggs

 

[Rod Snell]

So, for reloading purposes, how do you know how much powder to put in the brass? Do you start with half the bullet weight just for plinking (less $$)? Will a bullet that's 115 grain destabilize (meaning to breakup or disintegrate) if one uses too much powder behind it?

Thanks,

Braggs

The way you know how much and what kind of powder to use is to look in a good reloading manual.
If you use too much or the wrong kind, you may win a trip to the emergency room to have the pieces of your gun surgically removed.
If you read the front section of any good reloading manual, you will find an explanation of the principles of reloading, which must be firmly in hand before doing any reloading. It's not rocket science, but trial and error is not a viable way to learn.

Added: Link to reloading data
http://data.hodgdon.com/main_menu.asp