...one rifle I own is a 338 win mag.... these cases hold a lot of powder....
I have not calculated the amount of cases that I can load with a pound of powder for a 338 mag but I would be surprised if it was +100......
The heaviest load shown on the Hodgdon Reloading Data Center is for 72 grs of IMR7828, for sure, you'll get less that 100 rounds loaded from a lb of powder, most loads average around 65 grs, netting you almost 108 rounds. Currently, I'm loading 200 gr SPR SP over 62.3 grs of IMR4895, and get a whole 112 rounds from a 1 lb can. Not like I want to sit down at a bench and fire all 112 rounds at the sitting either!