First I want say thanks to Pause at Pacific Nerf for making a post about this!
This is a very simple breech, it took me about 5 minutes to make. So, normally you would use 1/2 PVC to make a CPVC breech. I used a AT2K pump tube as the guide. Here's some pics:
Here's some custom barrels for it.
two videos I made with it:
Thanks for reading