This might not be the ideal site for your interest...

Seems most of the fellows here tend to discuss european sporting and dangerous game type rifles.
Do a little google-ing and look for Cheyenne Tactical.
They have developed a .40 caliber long range system that's more accurate than the .50BMG can be and seems to impart greater terminal energy at longer ranges than the big .50

Good success in your search.

Have you thought of light field artillery like the recoiless rifle?

--Tinker