I have a couple of .35 Whelens that I absolutely "dote on" (MK X and 7600). I reread all the "posts" related to loading the Whelen of loading with RL15, plus many other powders. Like many of my "fellow loaders" I have been perplexed at Alliant's fairly recent "downloading" of the cartridge with RL15 powder and have read all the various explanations to include the switch from "CUP" to "PSI", custom chambers, powder "lots", etc. The Whelen cartridge was first "tagged" as being certified for loads to 52,000CUP, or about 62,000PS, although (supposedly) there is no "linear formula" for computation. The pressure given by alliant lists the Whelen in PSI, while showing the pressure below the max CUP pressure normally given prior to the "Pezio" pressure tests. When Alliant has been asked about the discrepancy of listing a "previous" 250gr load at 59.5 grain of RL15 and now listing the max for the same bullet at 54.0gr they do not seem to know how they arrived at this decision! (At least, I have never read or heard of their official reason for this 10% reduction.) I have been reloading the Whelen for a couple of decades now; and when I first started reloading it, I used some of the data provided by Finn Aagaard. I have several bottles of RL15 and I regularly load 57.5gr of the "stuff" behind at least 3 different brands of 250gr bullets. I have even loaded up to the 59.5gr limit (mine, at present), but most are more accurate with 1 or 2 less grains of powder (pretty typical). I have yet to have any of the "typical" pressure signs, even when using "Lake City" 30/06 brass, which BTW does not have a 30/06 "head stamp".
My theory is: I believe the switch to PSI versus CUP caught Alliant "flat footed". They equated PSI to be much the same as CUP and listed even lower pressure because of the "likelihood" of overloading a "former Wildcat" too high during the transition. I can't prove this, but other sources seem to follow the manufactures (Alliant's) lead, while most Whelen "users" tend to use the old data with complete satisfaction, including this one. I think that if Alliant went back and boosted their pressure levels back up to 62,000PSI they would then up their chronograph velocities back up to the 2450 to 2500+fps range. To have a smaller case like the .358Win "outrun" your favorite 30/06 based cartridge is an "embarrassment"! I just don't think the Whelen was treated fairly! my .02
