<<<>>> This carabiner is NOT DESIGNED FOR CLIMBING or any purpose where human safety is at risk!

Inspired by https://www.thingiverse.com/thing:2565902. This custom design uses the same center spring gate style. The gate spring was thinned to allow for greater gate deflection due to the redesigned carabiner frame.
The Simple Carabiner that this was based on was a brilliant design. My sole purpose for the redesign was to gain more clip over clearance. The 50% version can now clip over a 13mm round object and the full size can clip over a 1 inch object. The gate and frame were also modified for better gate retention under load.

The .STL files are available for full size as well as 80%, 60%, and 50%.
You can of course just download the full size carabiner and gate and then scale them in the slicer to get your desired size. You may not get good results below 50% without using less than a .4mm nozzle.

For best results, print with the following wall thicknesses:

Carabiner= 8 walls thick (IMPORTANT FOR SOLID SPRING BELOW SLOT)
80%= 6 walls or 2.4mm
60%= 5 walls or 2.0mm
50%= 4 walls or 1.6mm

Gate= 10 walls thick (IMPORTANT FOR SOLID CENTER SPRING)
80% gate= 8 walls or 3.2mm
60% gate= 6 walls or 2.4mm
50% gate= 5 walls or 2.0mm

Printing with less than these wall thicknesses may result in fatigue cracking of the springs.

3 top and bottom layers work great.

The approximate sizes are:
100%= 107mm or 4.2 inches
80%= 86mm or 3.4 inches
60%= 64mm or 2.5 inches
50%= 54mm or 2.1 inches

Update 5/27/22
I uploaded a slightly curvier version of the simple carabiner in case someone likes the ear shape better.

Carab.stl is the straight frame version
Carab2.stl is the curvier version

There is little difference except:

1) There is a slightly larger radius at both the top and bottom of the frame to better fit large round objects like broomsticks or shower rods, etc.

2) There is a slightly greater angle at the top of the frame to ensure that the clipped over object slides up close to the back spine for greater strength rather than getting stuck by the gate where the carabiner is weaker.

The original straight frame carabiner works great for clipping over belt loops or wide backpack loops because the top is flatter and a little closer to horizontal. They both clip over approximately a 1 inch round object when printed full size.

Mostly it comes down to your preference in shape. Print them both and see which one you like better!