Today I started machining a chamber for a hybrid that I have wanted to build for a long time. I recently started studying to be a machinist so I now have access to large lathes and mills to do my projects on. Here is a picture of the partially machined chamber: It is 143mm OD, 75mm ID and about 270mm long at the moment. The OD is in its final dimension but the inside surface has not yet been machined, so it will probably be 77 or 78mm, depending on how much the hole is off center, I havent measured that yet but it is in the 0.5-1mm range. It will have a chamber volume of about 1250-1300cc depending on the final chamber ID.
I have done some pressure simulations on it in AutoCad Inventor, it suggests that I could do 75x shots with butane with over 2.5 safety factor. This simulation is with 700 bar continuous pressure:

The steel the chamber is made of has 355MPa minimum yield pressure, so the max of 170MPa stress suggested by the simulation is nowhere near its breaking point. According to HGDT simulation at 75x my max chamber pressure will be 530 bar so the stresses will be even lower than in the simulation picture above.
Just wanted to share my project here and I will post my progress as I get more machining done. I currently have machining classes every thursday in this period so you can expect more progress next week. I am sure I missed something so be sure to ask.