The broken gun's range is 1 square to all sides
New variant Idea

interesting but i think the "gun" capture should be different from the regular one
Thats the why I put the name of the gun of broken gun but yeah if I would change its range, I would put it like in a range of 3 to the 8 directions (Queen directions), but I wouldnt put it like in knight range because the bullet isnt affected by gravity, but maybe can just change the weapon from broken gun to bow instead.

And there is a big difference between gun capture and classic capture, even if they have the same range
Gun capture:
Whites turn
Classic capture:

And there is a big difference between gun capture and classic capture, even if they have the same range
Gun capture:
Whites turn
Classic capture:
...
In this variant, both Kings are equipped with a broken gun, In which allow the king have 2 different kinds of captures:
1: Classic capture
2: Gun capture, in which captures a piece without moving the king himself, but costs 1 of ammo
If kings ammo go to 0, the king wont be able to do the gun capture for the rest of the game.
Get stalemated with 1 or more of ammo remaining is a lose.
Each king has of 3 ammo