I will say it will be a German collector digging through an archive that will find the indisputable answer, not some American fumbling around with rifles or trends!
This is from forever ago, but whatever I'm still going to reply.
I don't think it's likely that we'll get something from the archives, and personally I think there is probably a better chance of it coming from observations of surviving weapons.
Is it impossible that there could be archival material that answers this? No. There's always a possibility. But I consider it a very faint possibility. A huge proportion of the records relating to the Imperial military in general, and arms procurement in particular, were destroyed in WW2. Most of what remains has been pretty exhaustively cataloged and researched in the years since, especially when the disparate archival holdings started getting put back together post-unification. Again, not impossible, but I wouldn't hold my breath. Maybe a mislabeled box etc.
On the other hand, we are still in the relative infancy of research and trending being done on the weapons themselves, at least insofar as the holdings of American collectors are concerned. Even if you look at a place like this, with a ton of really impressive work done, what percentage of the total population of weapons in the US would you say we have direct access to? How many guns are there in the safes of folks who either aren't part of the collecting community (i.e. it's Grandpa's war rifle sitting behind some deer getters and maybe an AR) or are but don't post online? How many more are in non-private collections, e.g. museums and the like?
Note that I'm not saying I think there is a high likelihood of this being cracked by collectors, either. But it would surprise me a lot less than getting something definitive from archival sources.