Re: .257 Weatherby
250fps from 75 down to 45 degrees??? According to Ackley and my own chronograph data it's more like 1 foot per second for every 1 degree. I have chronoed ammo that was 150+ degrees that was sitting on the dash that had IMR-4831 in it and then chronoed again at around 45 degrees and it was only about 100 feet per second slower. I chronograph almost every shot when I am target shooting. Same results with Varget, H-380, RL-19, RL-22, IMR-7828, and IMR-4350 . I think all this extreme powder stuff is just a gimmick to sell more powder The extreme stuff varies just as much from what I can tell. I carry an infrared heat sensing gun when I'm chronographing to see how warm my barrels are or when I am doing any kind of volume shooting. I don't want to melt my 257Wby while shooting varmints with it.
I use RL-22 for the 75 grain V-Max's to get 3960 fps and IMR-7828 for 100grain Partition's to get almost 3700fps. The 110's I tried RL-25 and IMR-7828 and they were about the same thing powderwise but couldn't get any speed or as good of accuracy out of them. In my gun the 100's fly faster, shoot flatter and hit harder out to 1000 yards than the 110's. I might still try them on Elk because they are a heavier bullet.
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