Interesting about the high pressure loads prior to the appearance of the Super-X. But then SAAMI did not exist prior to WWI, so there were no voluntary industry standards for proof and service pressure. But it's always been my understanding--reinforced by various contemporary sources--that the Super-X actually INCREASED pressure with its 3 3/4 DE/1 1/4 oz load. The result being that Ithaca replaced the Flues with the stronger NID design, and Hunter Arms brought out the reinforced Long Range Wildfowl and Fox the Super Fox for those who were likely to be shooting a steady diet of those new loads at waterfowl.
Also interesting to note that all those pressure figures from before WWI would actually be LUP, not psi--which means they're even higher than the numbers listed, when comparing to modern loads.
