This little guide will help you solve the puzzles to get the weapons attachments you'll need to upgrade Jill's arsenal in Resident Evil 3.
G19 Handgun
They are 3 improvements available for Jill's G19 Handgun:
Dot Sight (Handgun)
Adds a laser pointer to increase precision and reduces Jill's aim stabilization time
On the streets of Raccoon City, you'll find yourself on a zombie-infested street downhill with an electric generator, go directly to the right and take the stairs.
Going right again, you'll pass through a door that takes you to a sort of shed. You will face a safe with a note next to it giving you a little clue to the combination. "Aqua Cure". As you continue through the streets, you will come face to face with a pharmacy. Inside it are ammunition and a green plant. But more importantly, an "Aqua Cure" sign at the back of the room will give you the combination of the trunk: 9 left, 1 right and 8 left.
All you have to do now is return to the vault and get your loot.
Extended Magazine
Increases the number of bullets in the magazine to 33.
As in the 1999 RE3, you can injure The Nemesis so that it drops crates at specific times. In these crates are sometimes very important items such as weapon upgrades. This is the case here with the extended magazine.
After restoring power to the Drain Deimos' nest, as you return to the streets of Raccoon City, The Nemesis will blow a wall to appear before you. That's when you'll have to put him down to drop the crate.
Silencer
Reduces the sound of Jill's gun and increases the chance of critical hits.
The method will be the same as for the extended magazine, you'll have to put The Nemesis down to get him do drop the crate of equipment. This time, you'll have to wait until you have to go back to the subway, more precisely the cinematic when The Nemesis turns his first zombie.
The M3 Shotgun
The shotgun will be your secondary weapon. Collecting the 3 attachments will be very useful.
The tactical stock
Reduces recoil and increases accuracy.
For this improvement, you will first need to have the Bolt Cutter which is located in the room just past the burning alleyway where you will be using the fire hose.
Once you have this tool in your pocket, go back to the Supermarket, right next to the subway station and cut the chain blocking the entrance. Immediately upon entering the store you will find a box. When you examine it, you will find the blue jewel inside.
Go back into the subway entrance, just next to the storage box is a display. Place the jewel and you will get the tactical stock.
Semi-Auto Barrel
Increases the rate of fire and reduces spread for more power.
Just after the battle against The Nemesis and its flame-thrower on the roof of the building, you'll soon find a shop quite familiar to fans of the license, the "Gun Shop Kendo".
All you have to do is enter the armory and search the shelves at the entrance, the semi-auto barrel is there for you to use.
Shell belt
Increases reload speed.
This item is unfortunately obtained towards the end of the game and will be of little use.
It's available in the hospital's underground warehouse, when you need to collect the fuses to start the elevator to reach Nicholai. The Shell Belt is in a white case in the maze that the U.B.C.S. member will create for you.
Magnum - Lightning Hawk .44 AE
As you might expect, the Magnum is making a comeback. Obtained quite late in the adventure, it will be reserved for the toughest enemies.
Extended Barrel (MAG)
Reduces recoil and gives more speed to the balls, increasing the damage done.
Available in the hospital's underground warehouse, you'll first need to find the three fuses to restart the elevator. The white case containing the long cannon will be located between the checkpoint and the window.