Is there any difference between black and red rounds? Why did they stop making black ones?
There was a great article about these plastic Exerzierpatronen in the IAA Journal from July 2015 (Issue no 504 pages 56 - 66) by Lew Curtis and Leon Kranen
I think the red plastic was better visible for the recruits as black.
Perhaps interesting to know.
The plastic black was made by the companies;
Both also exist without a head stamp.