From Enter the Gungeon Wiki
Lower Case r is a gun that fires a burst of 6 bullets that spell out the word BULLET.
Hacker - If the player also has Bracket Key, damage is increased by 25%.
Rabid - If the player has Angry Bullets, the words LOSER, DORK, CHUMP, NOODLE, and TAFFER are spelled out.
Radiant - If the player has Silver Bullets, the words SILVER, BLESSED, and WEREWOLF are spelled out. When it shoots "WEREWOLF", the firing sound is "DIE WEREWOLF DIE".
Ravishing - If the player has Charming Rounds, the words HANDSOME, CHARM, and CUTE are spelled out.
Reactive - If the player has Explosive Rounds, the words ROCKET, BOOM, KABOOM, and POW are spelled out, and shots become explosive.
Reanimate - If the player has Ghost Bullets, the words SPOOKY, GHOST, and BOO are spelled out.
Reinforced - If the player has +1 Bullets, BULLET+1 is spelled out.
Remnant - If the player has Omega Bullets, an omega appears after BULLET.
Research - If the player has Book of Chest Anatomy, the words CHEST and MIMIC are spelled out, and the gun can unlock chests.
Resplendent - If the player has Gilded Bullets, the words CASH, COINS, SHELLS, and GOLD are spelled out.
Root - If the player has Alpha Bullets, an alpha appears before BULLET.
Runic - If the player has Magic Bullets, the words ABRA and KADABRA are spelled out.
- All synergies that affect what letters Lower Case r fires increase the base damage per letter from 2.2 to 5.
- The voice that says the words shot by the gun out loud belongs to Doseone, the game's composer.
- The reload animation consists of deleting the letter, through use of backspace, and typing a new one.
- Lower Case r's bullets leave behind the word BLAM!! whenever they hit something.
- This could be a reference to old ASCII Adventure games, where letters would commonly be used to represent items, pickups and weapons based on their visual similarities.
- The pickup quote "Alphabetical!" could be a reference to Finn from Adventure Time exclaiming "Mathematical!"