Closer and closer...
I used Microsoft Visio to draft this case design. It is now closer to being finished I believe this is fairly close, probably "close enough" to the original that I'm imitating. You will observe that when I lay my line drawing over the "factory" photo, it almost perfectly matches up
I have some tool steel rod (o1 I think) that I am going to use to build the actual reamer. I need to compute the size for the chamber. I will make a chamber casting of a 7.62x39 chamber and compare that to the line drawings of 7.62x39 cartridges in all my reloading manuals. I will compare that to the 7.62x39 reload sizing die to verify the difference in sizes.
Actually now that I hink about it, I may pull out my other country builds - Hungarian, Yugo, Romy, and Chinese, to get an average size between them.
That SHOULD give me a really close idea of how much larger the chamber needs to be. As discussed on recent threads, I think this will be .003" larger. It would be less if it were a match chamber, but according to the reamer design info I've found on the web, I think .003" is a good number that will provide reliable operation in a semi.
This diagram is incomplete - I still need to insert the diameters at the neck.
The more I look at it, I think brass will be tricky. I'm not sure if 7.62x39 can be fireformed and keep that large of a neck. Ditto for PPC brass. I may be able to use Grendel brass because this will be longer than a Grendel.
I originally set the shoulder at 30 degrees. I was surprised to see that the shoulder angle is still 17 degrees, just like an AK. It certainly LOOKS steeper, I was guessing 25-30 degrees, but the angle tool indicates it is right at 17. MAYBE 20, but I don't have a better picture to work at. I'm still undecided on whether to keep it at 17. Now that I think about it, my 7.62x39 headspace gauges may work if I keep it at 17 but I need to look more closely.
That big bullet takes up a bunch of room on the powder, huh? I wonder if they use a "compressed" load?
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