Gippeto, no powered feed on the Sherline so I'm restricted to taps and dies for cutting threads, which is the machining operation I dislike the most, so pinning it is
![Smile :)](./images/smilies/icon_e_smile.png)
Now that this has some chance of working I've progressed to the next stage of planning being what sort of blowback mechanism would be best.
![Image](https://i.imgur.com/hzN6cfa.gif)
"closed bolt" mechanism with a separate spring-loaded firing pin.
![Image](https://i.imgur.com/qk0e0FD.gif)
"open bolt" mechanism with a floating firing pin.
I'm inclined towards the latter, it's easier to build, perhaps less accurate due to greater movement before firing but that is not really a concern for what is meant to be a plinker. It will also cycle on full auto as long as the trigger is pressed, the closed bolt would be more difficult to implement as a select fire device. Not that with a limited amount of cartridges that would last very long anyway.