Yes and no. From an energy perspective, they are nearly twins. However, there are a lot more bullet options for the 338. The 325WSM is a fine and capable chambering. I have some friends that shoot the wildcat 338-300wsm and it is essentially the equal of the 338Win Mag but in a short action. Although the WSM's have less case capacity than the 338WinMag, they are loaded to higher pressures to make up most of the difference. If you are reloading, I believe the 338win mag is superior to the 325wsm. If you're not reloading ???
In comparing the 325wsm and the 338win Mag, there are many things to consider. The 338WinMag may have a larger magazine capacity, be easier to find cartridges for and has a much better selection of bullets than the 325wsm.
In short, from an energy perspective, they are very close; but thats about it.
AJ
