I cant speak about any of the guns that came with single triggers, but if they only made 10, seems like a rare bird. That said, no idea how many single trigger assemblies they may have made to put into guns, but I knew where there was a stash of them, around 25 or so. Coincidentally, that stash was not far from Remington itself. However those guys sold a warehouse full of parts to Numrich not long ago, those parts may have been included. If so, you may see them starting to appear more frequently.
