Some of the weapons in Resident Evil 3 Remake can be fitted with attachments that improve their performance. These include upgrades to magazine capacity, stability, power, and more. To equip an attachment, simply combine it with the corresponding weapon. Bear in mind that some attachments make the weapon occupy two inventory slots. If you change your mind after equipping one of these attachments, select "Remove Part" from the weapon menu. The part that increased the weapon's size will return to your inventory. Attachments that don't increase the number of inventory slots occupied by a weapon cannot be removed.
The G19 Handgun supports three attachments:
It is obtained by opening the safe on Redstone Street. It improves the Handgun's accuracy.
In Downtown, after restoring power at the substation, Nemesis will break through a wall while you are returning to Redstone Street. If you manage to knock him down, he will drop a Supply Case containing this upgrade. It increases the Handgun's magazine capacity to 33 rounds.
In Downtown, after setting the subway route and returning to the station, you will see a cutscene in which Nemesis infects a zombie. If you knock him down during this section, he will drop a Supply Case containing this attachment. It causes nearby enemies to react more slowly to gunfire and increases the chance of inflicting critical damage. It makes the Handgun occupy two inventory slots.
The M3 Shotgun supports three attachments:
It is obtained by inserting the jewels into the monument during the jewel puzzle. It improves the Shotgun's stability and accuracy.
After the battle against Nemesis at the Demolition Site, you will need to pass through Gun Shop Kendo. The barrel is on one of the shelves to the left of the door. It increases the Shotgun's accuracy and power while expanding its capacity from four to six shells.
It is located in the Hospital Underground, inside the Underground Storage where you must collect the Fuses. Lower the hydraulic lift in the southeastern corner and walk across it to reach the other side, where you will find the case containing the attachment.
The CQBR Assault Rifle supports three attachments. Bear in mind that they can only be equipped to Carlos's weapon. Attachments cannot be applied to Jill's Assault Rifle, whether it is the weapon available on Assisted difficulty or the infinite-ammunition version:
It is inside the locked case in the East Office on the first floor of the Police Station. You need the ID Card to open it. It improves the weapon's accuracy.
It is located on the second floor of the Hospital. In the southwestern corner of the hallway, you will pass a broken window surrounded by bloodstains and yellow tape. Jump through it to reach the attachment. You must jump through the first window, not the second, which leads directly to a key. The Tactical Grip improves the weapon's stability when firing continuously.
It is located inside the Nurses' Station safe on the second floor of the Hospital. The combination is 9 left, 3 right. It increases the magazine capacity to 64 rounds.
The .44 AE Lightning Hawk only supports one attachment.
It is located in the Hospital Underground. After inserting the Fuses, you can take the elevator to the Surveillance Room. Once there, search the southwestern corner near the window to find the case containing the Extended Barrel.
