At the moment I figure it was a cut down long rifle that was made into a short rifle for some nation who likely didn't have spare parts for the weapons system. Wouldn't be a hard conversion, just cut a bit off the barrel, cut down the thickness at the end slightly, and remount the front sight. As a machinist I could do that in 2-4 hours. I think short rifle is really about the best term your going to find for it as I doubt whoever was using it at that point was calling them by the original designations.
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