Bolt Action Pen

Inspired by the bolt-action pens made by [Mussy](https://www.thingiverse.com/thing:2825430) and [Begal](https://www.thingiverse.com/thing:2441657). They are good designs but I was dissatisfied with several aspects on a purely personal preference level.

I wanted a design that didn't require additional hardware beyond the pen insert and spring, and was easily adjustable to accommodate a wide range of pen insert sizes.

The bolt design includes a built-in lever with the endcap closing off the slide channel of the body, capturing the bolt. The body is wide enough and the length of the bolt can be easily altered to fit the length of most pen inserts I could find dimensions for.

Possible future features:
Alter the endcap to be screw-on or twist-lock instead of an interference fit.
Texture the grip area of the pen