Odd 7.7x58 Loadings

I’ve had the brass-cased round for a bit, recently got the steel case example. The left example has a rough steel case with a blackened steel bullet. The round on the right has a brass case, blackened base, and blackened GM bullet. Any thoughts or ideas on the loadings; ball or something different?

Are you sure that the jackets are GM? According to Ken Elks’ invaluable booklets on Japanese ammunition (recently revised), the blackened bullets are a rare variation on the standard ball round. It is believed to be a treatment to prevent steel-jacketed bullets from rusting.

The steel-cased ammo was introduced from 1944 due to a shortage of brass. Elks states that the primers of the steel-cased rounds are not always ring-crimped like the brass-cased ones.

The brass-cased round on the right has a non-mag GM bullet, sort of painted black, while the other is a more chemical-looking blackening on a steel jacket.