Rifle Scopes Shadow at the bottom of reticle at lowest power?

[vicegripdog]

Hello Hide,
I'm new to precision shooting and I have a question regarding my scope. I have a Night Force F1, and I noticed at the lowest power of 3.5 I can see a shadow at the 6:00 position. It is shaped like a half moon. It goes away when I go up to 5 power. Does anyone have any idea what this is and what I need to do. I have it in Badger rings and used a Wheeler fat wrench at 15lb per inch to tighten the rings around it. Other than the shadow, glass is crystal clear and can't wait to test it out.
I hope the scope is not defective...
Thanks in advance!

 

[scudzuki]

Does it change when you adjust the elevation or windage turret?
Is what you're describing part of the FOV being obscured when the erector is at or near any of the limits of travel (bottoming against the inside of the tube)? I call it shrouding, and practically every scope I've seen with a lot of elevation travel has at least a little, like S&B PMII, Bushnell DMR, etc.

Joe

 

[bhart89]

How long is your barrel?

 

[vicegripdog]

There is no change when I adjust the elevation or windage, in fact when I turn the whole rifle sideways the shadow remains in the same place.
The barrel length is 20 inches. It's a Remington 700 SPS AAC.

 

[physhphude]

Mine does that too, it's the barrel on mine.