Do you mean Sin 338? I have seen no posted h20 cap. here are a few I have seen but dont know how accurate. 340 WM-93,338 NM-107, 338 rum -113, 388LA-114.LTLR LISTED on a thread this capacity w/h870, 330 Dak.-89.5,340WM-98,338 Sin-102.5,338 Rum-107. The Sin was based off 338 Rum original, there using 330 Dakto brass.The 388 Norma is based off 416 Rigby,same as 338lapua. Which has a larger rim. So in short not as easy or designed for some actions. I think the Norma has a slightly larger capacity. The Sin adapts to more actions for a retrofit and you still maintain your mag capacity, My Norma in a basic mag , hunting type, holds 2 rounds. There are 338 Normas ready to go such as McMillian tac 338, and Mikes Gun Sales has them also. New Shooter, I thought you had a 338 LA?