-It now has a 7 round capacity (there was a 6 round capacity in the D3)
-Improved magazine design (sturdier)
-Magazine can now be used as a suitable handle
-Magazine will not accidently slip out now (area around the mag has been built up slightly to atop this)
-More counterweight rubberbands can now be added without breaking the gun (to prevent accidental fire, and double-fire)
-Improved forward sight (this sight will be pointing perfectly straight, it won't be crooked, or won't fold down)
**NOTE: TO DO THIS INSTRUCTABLE, YOU MUST FIRST BUILD THE D3 Semi-Automatic Handgun from it's instructable: D3 INSTRUCTABLE**
The video is from the D3 Semi-Automatic Handgun, but even though this is the instructable for the D3.1, they fire exactly the same.
Step 1: Area Around Magazine Improvements
With this step done, you can now add more counterweight rubberbands onto the trigger (I added 1 more and that was fine for me).
Step 2: Magazine Improvements
Basically, you need to change the very top piece of the magazine, the part which holds the rubberbands (change from the 1x4 piece with 3 holes, to a 1x2 piece with 2 holes, on both sides), and extend the length of the magazine, as well as adding a new piece design to the bottom.
Step 3: Top Sight Improvements
This sight is just more practical to use.