Silly question, but look at this pic. You can see through the pin hole that locks the gas tube. All youtube videos show a solid pin being tapped into these and other AR gas blocks. So again, silly question, but is it possible this was pinned with a tubular type pin, that would explain seeing through it? I thought all pins for gas blocks are solid. Similarly, the pin next to the two set screws - on the bottom of the clamp, on the receiver side - is "see thru" too, though you can't see it in the pic due to the angle.