Before you make one, go to a sporting goods store, look at the gun "holders" or scabbards. You will find them in all kinds of fabrics. The ones I personally like are quite firm on the sides with lots & lots of padding, so the scope doesn't get bumped & get out of whack. (I think that is a technical term) lol. Also the most popular ones have a very l o n g zipper on the seam side. Very useful for getting the gun out of the case.
I have been an avid hunter for about 20 yrs. now, & to be honest, I've never thought to make my own gun case. Hum, maybe something in the fruit ladies line? Or some of the "hunk" fabric? Something a little more feminine?
I wish you luck.
Billie G