Ammo 101- It’s grain, not grains.
Grain is the actual weight measurement of a bullet—not the cartridge. If you want to sound like a newbie, call it “grains”—plural. If you want to know what you’re talking about, refer to is as grain—singular. The more a cartridge weighs the more grain it has. Standard weight for .45 ACP ball ammunition (full metal jacket – FMJ) is 230 grain. Standard for 9mm is around 115 grain. Generally the heavier bullet moves slower than a lighter bullet.
There is quite the battle raging among shooters as to which is better for defense. Some say to use a big, heavy, slow bullet for target penetration and some say to use a lighter bullet at higher velocity for expansion. Personally, I’m in favor of a heavy bullet with a good hollow point. After all, a heavy bullet still moves “at the speed of a bullet,” right?