Re: 338 LM improved, 338/300 RUM, 338/416
Depending on what degree of improving the wildcat design has you could see as little as 25 fps velocity gain or as high as 100 fps on this case. That said, the only way to get the upper end velocity gains is to reduce body taper to an absolute minimun which gives slightly more case capacity but at a cost of feeding and extracting with high pressure loads.
I would also like to agree with Uncle B. with these larger cases, after a few firings, the cases really lose their abilty to be sized easily and even a slight bump on the shoulder to get it back just enough for easy chambering can result in a colapsed shoulder.
A good neck and shoulder anneal can help this but with the smaller advantage in velocity you get I would really recommend the same and stay less then 40 degrees in shoulder angle.
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