All of the guns pictured in Winfer's books, or at least those taken by Tom Rowe, were taken with the rifle barrel slipped over a pin in a stand with the rifle muzzle down with a white backdrop.
When using a backdrop, make sure your gun is about a foot from the background to mitigate shadowing on the background.
The white background is the easiest to work with for use in books.

There is cheap software available to enable you to take the pictures with a green screen background so you can add whatever background you would like as well.