Somehow I missed this thread, - I wonder what else I have overlooked... this rifle is rather interesting, try and show more of it. You are correct in that this is unusual, not so much that it is a bcd made barrel (which it is), quite a few are known, but this is the earliest I have recorded it on a straight Army bcd 98k.
Believe it or not, but apparently bcd was experimenting with making barrels long before Gustloff II at Buchwald opened for business (rifle making business), 1940 and 1941 dated barrels are known, though extremely rare and typically on late production, clearly rejects that were pressed into service.
Many know that the various postwar reports and holocaust books on Gustloff speak of Gustloff Weimar making rifle barrels and stocks, but in reality this subject is really difficult to see in actual practice. I half suspect bcd stocks were in regards to G43 production, as i have not been able to fully document a Gustloff made 98k stock. A few might be Gustloff made, but typically the owners/sellers didn't illustrate the rifles well enough to determine if these are distinctly bcd made. This is not the case with barrels, we know for a fact bcd made quite a few 98k barrels, the vast majority on bcd/44 production, but some show up in 1943, none earlier than this rifle. A significant number of these barrels show up on commercial assembled rifles, not Army production, and typically the barrels are rejects that were used for this purpose, probably because they failed acceptance.
All of this begs the question of whether the holocaust books are correct in their apparent conclusion that these barrels were made at KL Buchenwald, they could have been of course, but if so the handful (4) 1940-1941 dated barrels would have to be explained. It is possible Gustloff began the barrel making at Weimar and later moved it to Buchenwald when it opened, - for no 1945 dated barrels are known and the operation could have been ended when Gustloff II was bombed in August 1944.
Anyway, this is an interesting rifle, mostly because of its barrel, which is the earliest use I have recorded for bcd Army production.
I think the bcd barrel is rather uncommon... marked "A.43 bcd"