The right way to do it is to use a Sabot and shoot a 338 in a 50 BMG ( .509 ) - you only get about 3 MOA but if they could figure out how to make it fly straight the physics is on your side. For a given pressure the Acceleration is directly proportional to the square of the caliber but the drag once you leave the barrel is proportional to the cube of the caliber. That's why the Abrams tanks is such an effective Kinetic Energy Tank Killer ( Depleted Uranium is twice as dense as lead and it uses a Sabot) ALS
has a vendor building Sabots to shoot 338's out of a 50 BMG - if they could get them down to 1 MOA it would be the ultimate long range gun.
Image shooting one Richards Wildcat 350 gr. .95 BC .338 at 4,500 FPS. It might just punch thru the gong at 2,500 yards (if you could hit it).
Notice the Sabot comming apart in the pic
consider a couple of incidents out of Desert Storm. On one occasion, an M1 fired its 120mm gun at an Iraqi T-72 (Soviet built) tank. The 120mm Armor-Piercing (SABOT/uranium-depleted steel dart) round went right through the T-72 and into another one directly behind it, destroying both tanks.
Another more amazing M1 story happened during the 24th Mechanized Infantry Divisionís run to the Euphrates River. It was raining heavily, and one M1 managed to get stuck in a mud hole and could not be extracted. With the rest of their unit moving on, the crew of the stuck tank waited for recovery vehicles to pull them out.
Suddenly, as they were waiting, three Iraqi T-72 tanks came over a hill and charged the mud-bogged tank. One T-72 fired a High-Explosive Anti Tank (HEAT) round that hit the frontal turret armor of the M1, but did no damage. At this point, the crew of the M1, though still stuck, fired a 120mm SABOT round at the attacking tank. The round penetrated the T-72ís turret, blowing it off into the air. By this time, the second T-72 also fired a HEAT round at the M1. That also hit the front of the turret, and did no damage. The M1 immediately destroyed this T-72 with another SABOT round. After that, the third and now last T-72 fired a 125mm Armor-Piercing round at the M1 from a range of 400 meters. This only grooved the front armor plate. At that point, realizing that continued action did not have much of a future, the crew of the last T-72 decided to run for cover. Spying a nearby sand berm, the Iraqis darted behind it, thinking they would be safe there. Back in the M1, the crew saw through their Thermal Imaging Sight (TIS) the hot plume of the T-72ís engine exhaust spewing up from behind the berm. Aiming carefully through their TIS, the M1ís crew fired a third 120mm SABOT round through the berm, into the tank, destroying it.