I have an Elite 3200 1.5x-4.5x-32mm with Warne Quick Detachable rings on my Winchester M70 Classic Stainless in n.375H&H Mag and the same thing happens when the power is in the 1.5 to about 3x or so range.
I don't know the height of your scope rings, but essentially any way you look at it, when the power is low like 2.5 or so, you can easily pick up seeing a portion of your barrel. It can be kind of annoying in the beginning, but you can get used to it. It has very little to nothing to do with the scope, just the magnification.
I normally have the power on most of my rifles in the 4x or 5x or so range, and then I bring it up if I need to.
Shooting 1/2" groups is great, and I wouldn't do anything to the gun, scope, or rings. Just keep on having the great success you have been having! :-D