1) DxWnd [sourceforge.net]
2) Borderless Gaming [github.com]


1) Start Gunlock
2) Go into the options, select video and set your resolution to 1920x1080
3) Close the game
4) Open DxWnd
5) Right click and select "add"
6) In the Main tab, click on the "..." icons for both Path and Launch and select the Gunlock executable "gl.exe"
7) Under the Generic tab, select "Run in Window", under Position, set the resolution to 1600x900, setting it higher will crash the game on startup
8) On the Input tab, go to the Cursor Handling menu and select "Correct Mouse position" and "Force Cursor Clipping"
9) Press ok, keep the program in the Background and open gunlock again
10) While Gunlock is running, open Borderless Window, Look on the left column for Gunlock (It should be called Gunlock [gl]), click on it and then click on the ">" icon
11) Congratulation, you can play Gunlock in Bordeless Window now

If anyone finds a less convoluted way, feel free to add it in the comments and ill try to update the guide ok bye