I wonder if someone will make a modern version, someday, for a common cheaper rifle like a Ruger American or Savage 110.
Those drop in kits to turn an AR-15 into a .22lr sort of follow the idea.
I think the biggest bottleneck for this concept in private use is the rifle and pistol rounds having to share diameter, and aside from the 5.56 and .22lr, there isn’t much common overlap I can think of. 7.62x25mm isn’t exactly falling off the shelves.
I think I’ve seen this depicted before. I’m guessing you’d have to look down the side of the barrel for aiming with this on?
Why would you need to look down the side of the barrel? The magazine doesn’t look like it’s blocking the sights in the photos.
Oh, I only saw the one angle. I didn’t realize it goes up and to the side.