Ah yes the good 'ol Bizon magazine! I've been searching high and low, and would love to get my hands on one. Definitely on my list as a must-build item
I agree that the Calico mag wouldn't really work as-is, and to make it correct you'll really need to rebuild the feed ramp area.
I've read that the Russian engineers essentially re-invented the Calico mag then changed the design to avoid copywright infringement. True or false I don't know, but it is different irregardless.
I've exchanged some info with Rhino_66 on this and back in the day I was going to build it completely in aluminum. Given today's composite materials (plastics) I am considering doing it in all synthetic. I still have the ABS tubing I plan to use as the basis for the magazine housing, and the springs.
I am thinking the best way to do it will be to imitate the Chinese-style drum magazines, and just imagine stretching that out and shrinking it down. Take the basic winding mechanism which will be super-easy to build and pin it to the synthetic/aluminum helical follower.
The follower is the trick. I've searched on machinist how-to forums for information and essentially there's two ways to make them on a lathe - first is to make it like you do when threading a rod like when making piston threads. The problem is the "thread pitch" will be so high that the machine will really be moving fast to get it to cut, and it will take forever.
The other way will be to use a special reducing gear for helical threads. That sounded expensive.
I am considering making an original out of wood, then using a mold for either aluminum casting or plastic casting to build the final product. It should be relatively simple either way, since casting in either medium is a known skill. Getting the original is the trick. Seeing as how decorative items like candles, wood spires, etc. are made with a helical twist, the wood original may be doable on a wood lathe with the right attachments.
Now, consider this - the Bizon is apparently built in several different calibers. Given the design of the helical feed, the magazine *may* be able to work with different calibers, provided you have some sort of bolt-on feed lip that can be swapped out. If for example you cut off the top of a PPSH magazine and left enough meat on the sides to let you bend out the bottom and use that to bolt it to the magazine housing, presto you have a 7.62x25. Then cut off an Uzi mag and bolt it on the same way, presto you have 9mm, .40 SW, .357 SIG, etc. all with a hot-swap "feed tower". JUST LIKE the Beta C-Mag feed towers let it convert to different rifles!
Every couple of months I collect another part for the build which is a pet project to me. I already have the 9mm barrel, and I have set aside a 7.62 barrel that I need to sleeve for 7.62x25. I just picked up a ton of 7.62x25 as well! The trunion isn't a big deal - just a rectangular piece and since it is blowback there really isn't much that needs to be done. Molding those handguards will be a hassle. I was thinking fiberglass resin at first, but again, plastic resins being what they are today, it shouldn't be too big a problem to do it straight from plastic.
The carrier/bolt combination is going to be a hassle. I was originally going to start with an Uzi bolt but after seeing some of the more recent BIY blowback builds, I will probably build it from scratch. I have a chunk of 4340 which is HARD HARD steel. I really think it is overkill and won't be necessary for the pressures the pistol calibers will generate. I'm going to use some 4130 steel instead since it is easier to work. It will have to be a two-piece item that is welded together, because I can't see how to cut the bolt face with the spring tube on top.