Grains per pound is finished arrow weight. It is calculated by taking the overall finished arrow weight, divided by the draw weight. ex. 500 grain arrow at 70 lbs. 500/70 = 7.14 grains per lb.

Grains per inch is the unfinished arrow weight.. ie- the bare shaft. ex - 9 grains per inch shaft x 30" shaft = 270 grain shaft..keep in mind however, that this is without insert, tip, nock, and fletchings.

Also, Arthur, excellent post. Probably the most thought out and best illustrated post I've seen here in a few years. I tend to agree with you. When hunting, the added momentum of a heavier arrow, more than makes up for the loss of trajectory. Especially with rangefinders.