Whats the eye relief for your scope that you have mounted on your shotgun?

Never was taught or showed anything like that. So I mounted mine what seems comfortable. It's about 5" give or take 1/2". But that was in short sleeves, thats why I said give or take. When someone who knows replies I'd be willing to listen. Guess it all matters what works for you.

The eye relief is the max amount of distance your eye is from the eyepiece of the scope to obtain a clear picture (no black circles). This max. amount is determined by the manucaturer of the scope (ie: 4" or 5"). How you mount the scope to encompass the eye relief is based on your shooting position and is personal to that shooter. But basically set the scope so it is at the max eyerelief for your shooting positions by sliding it in our out inside the rings, before you clamp it down (the objective is to not have to move your head forward or backwards to obtain both eye relief and unobstructed site picture). One caution though if you have a variable scope with variations in eye relief that changes with power setting it is important to test it at higher power to ensure you do not get a black ring or require a head positioning that is a stark difference to your shooting style. Most guys will set it up at max power or lowest eye relief available to that scope therefore ensuring it always remain clear and is comfortable through the power adjustments. If a fixed eye relief or fixed power scope this point is moot!

if you have a shotgun I'd say a minimum of 3.5" .....did you get that scope zeroed yet ?

What I like to do is leave the scope mounted loosely in the rings, so you can slide it back and forth easily. I then take the gun off the cradle I'm using to mount the scope on. I hold the gun at my waist and close my eyes. I then shoulder the gun as if I'm getting ready to shoot from a standing position. I then open my eyes and check to see if I have a full field of view through the scope. This keeps me from twisting my head and neck to adjust my sight plain to the scope. I do this several times before I lock down the top half of my scope rings. You want to move the scope to fit your natural shooting position and not alter your shooting position to fit the scope and the way it's mounted.
I am no expert but it seems to be working for me.
Good luck...
Jim B.

Most scope manufacturers make optics specifically for shotguns. These have an eye relief of around 5 inches to protect the shooter in consideration of the recoil of rifled slugs.