LRF,
In the late 1950s, my friend Gene Enterkin came up with the 358 Enterkin( he said it came to him in a dream),which is a full length H&H mag case blown out and necked to 358".One of his friends made the first reamer and dies. It runs a 250gr bullet over the screens at 3000fps also(no correction for distance to screen,altitude,temp, or anything)it was usually at 3008-3016fps.He marketed rifles and ammo, until he passed away 15 years ago.The avaliable bullets would not hold up to the velocity so he bought swaging dies and made his own bullets and marketed them also.His favorite was the 250gr bonded core boattail,but he also made dual core. He killed Cape buffalo, lion, plains game,and a "pile" of elk(one at over 500 yds., he commanded the Marksmanship Training Unit at Ft Benning,so 500 yds was no problem for him).He had his loads tested by HP White Labs before marketing the ammo.I was lucky enough to be able to buy the pressure barrel,reamers and headspace dies from his wife.You can tell I miss him.
Mike