My rifle is supposed to be in tomorrow. I had a pair of High Weaver Grand Slam steel rings on hand,and was planning on using the #45 bases to get a little extra height to mount a SimmonsWhiteTailClassic 6.5-20x50, which I also have on hand. It looks like it will work out about right, but I won't know for sure till I get the rifle. I have read numerous posts where the #45's are being used. I'm wondering if they are exactly the same contour as the receiver so that they snug down securely. All input appreciated. Gary