Absolutely stupid question.

[Ryan95]

I know this is dumb.
But I'm very new to firearms.

What exactly is the "grain" in ammunition specifying?

grain is a measure of weight ...437.5 grains = 1oz...

it is not dumb to ask , it is only dumb to choose to remain ignorant...you should see (and you will, if you stick around ...) some of the strange stuff people ask...

[Ryan95]

So the higher the grain means what.
Higher velocity?

[G19man]

The higher the grains, the heavier the bullet, and the slower the velocity. Light grain loads have the highest velocity out of the muzzle. You can search this site and see many discussion of the merits of "heavy and slow" loads versus "light and fast". It all boils down to which provides the best penetration. My own opinion is to stay in the middle of this spectrum, ie 124 grains for 9 mm and 155-165 for .40 caliber, however there are others here with lots of knowledge about this who may disagree.

[maxxx93]

Both the bullet weight and the amount of powder are measured in grains.
So if your talking about the bullet, more = slower.
If your talking about grains of powder, more = faster.

[ExNavyInHouston]

When you are looking at a box of ammunition and you see grain they are talking about the weight of the bullet portion of the cartridge.

Many phrases are often misused in ammunition. And bullet is certainly one.

Here is a basic break down of a typical pistol round.

Casing - houses primer, powder and grips the bullet
Primer - most dangerous part of the round. It is what is contacted by your firing pin and then ignites the powder.
Powder - Marterial which ignites and develops enough pressure to move the bullet out the end of the barrel.
Bullet - the projectile part of the ammo.

Often times you will hear someone use the term "bullets" incorrectly. Bullets are just a component of the whole cartridge or round.

Hope this helps.

Be sure to visit David Defabio's www.ammolab.com for unbiased testing results of various rounds in different calibers.

Charles