There are many ways to figure "efficiency," which is simply the actual compared in some way to an ideal. The "official" definition of a load's efficiency is the percentage of the powder's innate energy actually delivered as kinetic energy (cf Hatcher's Notebook). The innate, chemically bound energy of the IMR powders is (IIRC) about 178 ft-lb/gr, and a load that produces as much as 25% to 30% of this in the actual kinetic energy of the bullet at departure (muzzle) velocity is relatively very efficient.
<br>
<br>This definition of efficiency strikes me as pedantically neat but practically lacking and weak.
<br>
<br>I've already posted a breakdown of where the innate energy goes and will post it again when I find it again.
<br>
<br>Much more important -- practically speaking -- for the shooter (as distinct from the manufacturer) is effectiveness. A highly efficient load that isn't very effective in its intended use (not an unusual characteristic) isn't worth ol' Cactus Jack Garner's pitcher of warm spit to the shooter, no matter how profitable its efficiency makes it for its producer.
<br>
<br>The shooter-handloader is more interested in practical "efficency" as figured in terms, for example, of delivered kinetic energy per thousand pounds per square inch. Or perhaps as how many thousand rounds he can fire before the accuracy of his barrel goes unretrievably south. The "official" efficiency of the most practically desirable loads is often a good bit less than ideal from the theoretical view of "efficiency."
