This is about how to make a spring gun or a realistic gun. It is simple and doesn't take as many pats to make, around 30 bricks, depending on the version. Then you can mod the gun however you want to.
How to Make a Spring Gun (Step by Step)
Place a 1x3 Scalable Brick 1s and rotate it so It is facing vertical. (brick that are placed will be highlighted in colors)
Place 2 Redirector 2x 1x 1s 04 and place them at the bottom of the placed 1x3 scalable brick 1s.
Place a Actuator 1x 1x 3 Top on the top of the 1x3 scalable brick 1s.
Add a Actuator 1x 1x 3 Bottom to the Actuator 1x 1x 3 Top.
Place a Scalable Brick 1s horizontal and in the middle of the bottom of the Actuator 1x 1x 3 Bottom.
Place 2 1x2 Scalable Brick on both sides of the Actuator 1x 1x 3 Bottom, facing horizontal.
Place 2 Scalable Bricks on the bottom ends of the 1x2 scalable brick.
Place as many as you want of Gun 2x 2x 2 on the redirector 2x 1x 1s 04.
Place as many as you want of Barrel 1x 1x 4 Flat on the end of the Gun 2x 2x 2 (when I placed the gun and barrels, I made their material steel).
Step 10 (Optional)
Place a 4x2x2 (Z=4, Y=2, X=2) Scalable Brick 1s at the end of the gun.
Place a Camera 2x 1x 1 below the previously placed 1x2 scalable brick, leaving the 1x1 scalable brick.
Place a 1x4 Scalable Brick just in the front of the scalable brick. Change the material to glass.
Place 2 Nameplate 1x 1x 1s at the end of the 1x3 scalable brick. Change the material to glass and change the text to: - - Rotate one of the nameplates so the hyphens are vertical.
Step 14 (Optional)
Place a Gun 2x 1x 1 on the opposite side of where the camera is placed, in the same exact spot.
Step 15 (Part of Step 14 / Optional)
Place as many as you want of Barrel 1sx 1sx 3 at the end of the placed machinegun.