I’m trying to set up a 410 single shot turkey gun. I mounted a Bushnell red dot on a rail and sighted it in with high brass dove loads at 25 yards. When I backed up to 35 yards with TSS, POI was low. I dialed the red dot all the way up and POI is still 6-8” low. All screws are tight. Any ideas what the problem could be?

I had a Vortex red dot that just wouldn't accept any horizontal adjustment a while back. Vertical would adjust just fine. Maybe that's the problem?

I would put the gun in a vice and see if the dot is moving up and down as you make corrections. I can’t imagine much difference between any load within 35 yards, especially with a shotgun like that, but I have had a 8” difference in subsonic vs supersonic with a rifle so I guess it’s not out of the realm of possibilities.

If it dot is moving but you just can’t get enough correction out of it, look for a 20 or 40 moa rail (if they make such a thing for those shotguns).

I had the same problem with a vennom. I bottomed it out, and it still wouldn’t move. Sent it back to them, them deemed it as non-functional, and sent me a new one. No problems with the new one.

I had a red dot to start dancing right and left throwing my pattern off every shot
One shot it would hit left and the next it would hit right

The pattern is consistent, I’ve just run out of elevation adjustment. I’ll try putting it in a vice and see if it’s tracking up and down. I think it is though bc the bird shot moved. I can’t find a higher rail online for a Rossi.