Gas tube looks good. Finishing nails work sometimes. I made a take down pin detent out of one once. It worked till I replaced the one that flew across the room.
I have that scope on my PA10. Yes no AO. Decent glass and the Nikon spot on app works with the retical. not bad for the money. I also have the 3x9 on my Beowulf. Works for me till I can afford something better.
Gap in the middle is where it clamps to the buffer tube. You could adjust the lop a bit by where you clamped it down tight. There are 2 nuts and bolts to tighten to clamp the brace down.
I had the trp operator with the full length rail. Nice gun. Softest shooting 1911 I ever shot. Shot USPSA and idpa with it for a couple years. Great gun wish I hadn't sold it but at the time I needed to pay some bills.
The pistol braces showed up today. They tighten down snug with more than 1 little set screw like the KAK. 1 buffer tube was a little smaller diameter and I had to put a couple wraps of duct tape on the tube so the brace would clamp down properly.
My 870 has hi base 6's first 3 shots. 3" 00 buck next 3 shots. Slugs last 2 shots. If I have to use the slugs i am beyond careing what i tear up. More 00 buck on the stock for reloads.
They used to have 2 1/2" shells before 2 3/4". I have a pretty 20 gauge with a Simmons rib and georgous wood letting dad use it till he has no longer a need for a shotgun. It was my grandfathers.