ammo...grain?

Question
When I purchase ammo for my Winchester 30-30, I am offered 2 options
150 grain, or 180 grain. What is the difference? Is the 180 grain perhaps a larger bullet, a larger amount of powder, or none of the above. I would also like to know if your answer applies to all other ammo.

Answer
The 150 or 180 grains is a measure of the mass of the bullet.  1 ounce equals 437.5 grains.  The amount of powder is also different (and measured in grains).  Each type of cartridge is designed to not exceed the maximum pressure that is allowed for guns firing that type of cartridge.  So, the cartridge manufacturer puts the appropriate amount of powder in the cartridge to get the best results without going over the max pressure (when the cartridge is fired, the burning powder causes a pressure in the chamber and barrel in the ten thousands of pounds per square inch range, thus accelerating the bullet).

The 180 grain bullet cartridge will have more powder, but the bullet will still not travel as fast as the 150 grain bullet, so the 180 grain bullet will have a little more drop at longer ranges.

This is true for all rifle ammo.

Hope this helps!

Dave