To get the Uzume RR4 sniper rifle in Destiny 2, you need to participate in Nightfall strikes when this weapon is in rotation as a reward. The chances of obtaining the Uzume RR4 increase with the difficulty level of the Nightfall strike, with higher chances in higher difficulties like Grandmaster Nightfalls. Sometimes, Grandmaster Nightfalls might even guarantee a drop of the weapon. You can check the current weapon rotation schedule to plan when to aim for the Uzume RR4.
For the god roll of Uzume RR4, desirable perks can vary based on whether you're focusing on PvE or PvP. Commonly preferred perks include Extended Barrel or Hammer-Forged Rifling for the barrel, Accurized Rounds or Appended Mag for the magazine, and Clown Cartridge or Snapshot Sights for additional utility. The Vorpal Weapon perk is particularly valued for its increased damage against bosses, vehicles, and Guardians using their Super, making it effective in both PvE and PvP contexts.