Lighting and position are very important. I agree with the above poster, a tripod can coax most cameras to produce some fantastic photos, even in low-light.
This was taken with an old 4 megapixel Fuji A400 point and shoot. I used a chair as an improvised tripod and morning sun from a window as a light source, never use a flash. Flashes have their use, but it isn't for snapping firearms. Also, try to avoid lighting that is too direct. Diffuse if you can.
Now, ideally, I would say a high-end digital SLR like a Nikon D700 or a Canon EOS 40D equipped with a macro lens and a couple of lightboxes is a perfect setup, however, perfection costs money.
When shooting on a budget, or doing anything on a budget for that matter, one must use what one has laying around. If you can't find or afford a tripod at this juncture, try a lamp.
The part where the lampshade screws in, up on the top, shares a thread pattern with camera tripods, so basically any lamp can function as an impromptu tripod.
Failing that, stack up a couple of books. The setup does not have to look glorious, just the results. I looked pretty ridiculous when I took the above photo, but you'd never know I was performing a feat of acrobatic tom foolery by looking at the picture.
Also, avoid the zoom function. It's always better to move the camera it's self, and since most firearm photos are fairly close in, use the macro setting (The symbol looks like a flower), this adjusts the camera for close-up shots.
In short, light them well, but avoid glaring light, keep the camera as steady as possible by any means necessary, and mess with the settings on the camera until you're satisfied. More importantly, though, take several shots. It never hurts to snap three or four of the same image, even if it looks just right the first time. You may just find a gem.
After all that, the camera shouldn't matter too terribly much, but that being said, if you're in the market for a low-cost, high-quality digital camera with an excellent capacity for close-ups, the Panasonic Lumix series, particularly the TZ4 and up, are some of the finest point and shoots on the market, and last time I checked (At the camera store where I worked, sadly bankrupt), they were going for around $200.
The intelligent macro setting is very handy, the color reproduction is top-notch, and the interface is very easy to pick up. Basically the best camera for the job short of a $500+ SLR.
Hope this is helpful, if a bit wordy.