Lightboxes are not bad, but they really take a long exposure to come out well, not full of shadowns, etc...
You can buy one from any big photowebsite for less then $50.. The one that I bought along time ago had a internal frame, that could be folding up, etc... Of course, the cheap metal inside had a memory, and it was too big for AK stuff.. I ended cutting the thing up, and just using the material with a homemade PVC pipe frame.
For lights, I used 500W bulbs that were "Kelvin" matched to sunlight.. 5000K I believe.
Digital Rebel camera, the cheapest Profesional grade lense (One that came with it was crap).
Set on a tripod.. Exposures were about 1 second.
For taking pictures of details, like markings, etc it was a royal PITA.... ALso, for moving it around, a royal PITA. Those 500w bulbs were super expensvie, and probably used allot of electricity.
Later, I switched to using 2x remoted, external flashes, with umbrellas. It is allot more portable, and the exposures are short enough that I can hold it in my hand, which makes detail shots easier. Also, you can actually use the same setup for other stuff; Pictures of the family, etc...
Honestly, I think overall the soft boxe shots look better.. But the trade offs from a flash set up are well worth it.
I skipped the "box" an bought 3 of the spun aluminum work lamps and 3 daylight temperature florescent lamps at the Home Depot. Set my speed at 400 and got this result. Be sure to expose for the rifle, not the light background. [Rifle is laying on a six foot Sam's Club plastic folding table] Photography is the same as marksmanship, the more shots you make, the better you get. I learned on film, in a darkroom. The digital age is cheap and easy in comparison. Learn the basics, the principals are the same as they were 100 years ago, aperture and shutter speed.