One shot is enough, lets see what 3 does…
The Anzio 20mm rifle is an American anti-materiel rifle designed and marketed by Anzio Iron Works. It is the first American anti-materiel rifle designed and mass produced for public sale with a bore diameter in excess of .50 caliber in over 80 years. The rifles are available in three chamberings: 20mm Vulcan (20×102mm), 14.5×114mm, and most recently Anzio’s own proprietary caliber 20/50 . The rifle’s predominant chambering is the 20mm Vulcan caliber.
Other notable features include an optional three-round detachable box magazine, a 49″ (1.24m) barrel, and threaded muzzle to accept either a muzzle brake or suppressor.
At approximately 38,000 foot-pounds (51,521 J) of kinetic energy, the 20mm round, as fired out of the Anzio rifle, has over three times the power of the .50 BMG cartridge fired out of a comparable rifle, which is around 12,200 foot pounds (16,540 J) of kinetic energy. The .600 Nitro Express, the second most powerful African big game rifle cartridge, and one of the most common, has around 8,200 foot pounds (11,118 J) of kinetic energy. This makes a 20mm Anzio rifle about 4.8 times as powerful as a rifle chambered in .600 Nitro Express.
The Anzio 20/50 has approximately 22,000 foot-pounds (29,828 J) of kinetic energy with an 800-grain bullet. It does this by effectively taking the .50 BMG projectile, which already is relatively large and travels extremely fast, and effectively increases the already supersonic bullet to over 1.3 times its normal flight velocity, creating more kinetic energy without the need for a larger and heavier projectile. Though its Kinetic energy is significantly lower than the 20mm round, it is almost as effective due to its smaller surface area, meaning that it has less material to punch through, making it easier to penetrate, but the lighter bullet makes transferring energy over longer distances and into targets less efficient.