The bolt pulls rounds out of the magazine, pushes them in the breach and fires them. Mine was made by laminating some 20-odd sheets of plastic together. Now it is a SOLID hunk of plastic! The metal strip on top is the extractor spring which I made out of metal from a picture frame.
The spring guide is a rod that acts as a guide for the bolt as it moves in the receiver. I used a long bolt, trimmed down the head with a grinder, and sheathed it with an aluminum tube. The bolt is pushed backward by recoil and hits a plastic stopper. For this I used laminated plastic.
I have not yet found a spring the right size for this part. It needs to be 5' long extended, 1' compressed, .25" inner diameter and you should be able to compress it with one hand. As I have looked in every local hardware store, I suspect I find it as part of some household gizmo. If you have a spring like this PLEASE contact me!
The bolt slides on the spring guide as shown. The spring will fit between the bolt and the brown piece.
The firing pin fits in the bolt face. For this I cut off a piece from a toy, put it in my hand drill and used a blade to lathe the tip. This piece is only 1/2" long.
When it's inserted, another pin locks it in place.
The safety on the PPSh-41 is a small sliding latch that locks the bolt in an open or closed position. It utilizes a small spring powered plunger to lock it in place. I had trouble finding a spring that small so I cut off a small piece of a rubber octopus's tentacle to push the plunger.
Unfortunately I couldn't build the bolt with an opening for the handle/safety because I wasn't confident that everything would line up correctly. After I marked the positions of the bolt in the receiver, I drilled, filed and cut the hole for the handle.
Once I glued it in place, a little sanding made it appear to be one piece. The handle is surprisingly solid although the spring I'm trying to find shouldn't cause that much torque.
Once again, please be on the lookout for the Mystery Spring. It could be anywhere!