I have solid head brass from Kynoch, Jamison, and Bertram. All new made with the past 20 year and less. Jamison has new name and rumor has them making 577/450 for commercial sales only.

I am also aware of Horneber making 577/450.

Rumor was that Kynoch switched from having Bertram making their brass to Prvi Partizan making brass for the 577/450. Ten-X was associated with this rumor as having sourced brass from Prvi Partizan also. Rumor- information not supported by fact.

A few years ago Richard Pomerantz? of Ten-x passed info on 577/450 brass from Jamison. We sold over 5000 rounds of this brass to members of British Militaria Forum in aGroup buy. The problem was Jamison didn't disclose the fact this was seconds until after we bought it and passed it on in the group buy.