ammo grain

Question
what is the difference in the amount of grain. for example the difference between a 135 grain and 165 grain. which is better for a .40? thank you.

Answer
Grain is a measurement of the weight of the bullet (the amount of powder is also measured in grain).  Various bullet styles are available, each having a standard size (weight).  For example, if you want a hollow point, it will have a certain weight available.  If you want a round nose full metal jacket bullet, it will usually be heavier than a hollow point.  Generally, a heavier bullet will travel slower than a lighter bullet if the amoiunt of powder is the same.  But different bullet weights often come loaded with different powder charges, so you'd have to check the specified bullet speed if you are interested in a certain speed.  

Actually, you would usually choose the bullet type that you want, and accept whatever weight it happens to come in as a factory load (unless you load your own cartridges).  For seld-defense use, you might typically want one of the bullet types that have a somewhat hollow point, with small cuts made around the nose that help to control expansion on pistol rounds.  These are available under many trade names.

Hope this helps!

Dave