If you are looking for a clean sterile picture showing our work one trick is to pick up some cheap white "foam board" from craft store
Overexpose the background with some cheap lights ( desklamp works ) pointing at the background ONLy ...this eliminates any shadows
Put rifle in front of the light setup
With the overexposed ( blown out background ) you only see the rifle
You can also go outside and because of "inverse square law of light" in photography....lots of videos online , if you put rifle close to you but have background far away you can have relatively dark background
You will need to use flash to make use of this technique
Background is underexposed ( dark ) since due to the inverse square rule, the light form flash does little to help with expose . Rifle properly exposed since its much closer to flash / camera
Only issue of both these techniques is you need to stand the rifle up ( not laying down ) . I have had many guns come crashing down as they were precariously set on table
I just sacrificed a magazine and made an tripod adapter