Sounds to me like someone is overthinking things.
When I used to make ramrods, and I have literally made hundreds of them, I called up the metal supply store and ordered a hundred feet of 3/8 and 50 feet of 5/16, etc. I was very happy with whatever alloy I got, and I never had a single complaint about what damn alloy I used. I don't think I ever had anyone ask about it. I know I sure didn't, and never thought to have asked.
If you go with the thought of obtaining a piece of brass rod, remember two things. 1) Allow for an extra 3 or 4 inches in the length for a handle. 2) Be sure to pin the rod into the handle. IIRC, I used 3/32 rod I got from the hardware store. Don't know what alloy that was, either.
For your .36 cal. rifle, I think a 5/16" diameter rod would be just fine. 5/16" = .3125" I like to use a rod thimble on my ramrods so if you use a jag with a 3/8" base, the rod thimble will not want to slide off the ramrod. You might have to trim a little off the base to fit the bore.
John (Bigsmoke)