How many .50 BMG IMPROVED cartridges have been done??? In what calibers??? I mean .50 BMG wildcas.??? I am sure that if there is a .338 or .300 BMG IMPROVED it will have a good velocity.

Thanks!

In cartridges of the world 9th edition, lists a few:
The 338/50 Talbot- It's a 50 necked down to 33 with a 35 degree shoulder, states use is long range targets out to 3,000 yards,dies by rcbs. Lists a 250sp with 170 grains AA8700 powder with a velocity of 3700 fps.

State Arms developed a .375-50 BMG Mach 5 that they advertised as performing 3500-5300 fps with a 300 grain, .375 caliber bullet. Gee, a .338 version launching a 300 grain Matchking at 5300 fps would almost obtain a stable ORBIT!!!