Excerpt from Gun & Ammunition Manufacturing Report (posted without comment, my emphasis)
The US gun and ammunition manufacturing industry includes about 300 companies with combined annual revenue of about $6 billion. Major gun and ammunition manufacturers include Browning Arms; Freedom Group (which includes Remington Arms, Marlin Firearms, and Bushmaster Firearms); Olin; Alliant Techsystems; Sturm, Ruger & Company; and Smith & Wesson. The industry is highly concentrated.
Competitive Landscape
Demand is driven partly by hunters, gun enthusiasts, and weapon upgrades by police departments. The profitability of individual companies is closely linked to marketing. Small companies can compete effectively by producing premium-priced high-quality or decorative guns. Although automation has increased, the industry is still labor-intensive: average annual revenue per worker is about $140,000.
Products, Operations & Technology
Major product categories include firearms and ammunition, each of which accounts for about half of industry revenues. The industry produces more than 4 million guns per year: about 30 percent are pistols and revolvers; about 40 percent are rifles, and about 30 percent are shotguns and other firearms. Within a category, a company may make guns of different caliber and style. The most popular pistol calibers are 9 millimeter, .45, and .22. The most popular revolver calibers are .357, .45, and .38.
http://www.hoovers.com/industry-facts.gun-ammunition-manufacturing.1200.html
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According to Dun and Bradsteet, in 2010, 661 establishments were engaged in manufacturing small firearms or parts for small firearms in the United States. Together these establishments employed 9,936 people and generated annual revenues of $1.2 billion. States with the highest concentration of employees included New Hampshire, New York, and Texas. Massachusetts accounted for the largest percentage of industry revenues, with $556.6 million, followed by Connecticut with $266.0 million.
Besides small arms manufacturers, major categories included manufacturers of products under 30mm, including guns (firearms), pistols, rifles, and shotguns as well as accompanying parts.
Projections for the industry in the early 2010s varied. For example, whereas a 2011 article in Shooting Industry pointed to the increase in NICS background checks for the fifteenth month in a row, reaching 815,858 checks in August 2011, signaled a positive future for the small arms industry, a report by market research firm IBISWorld noted that "demand for the industry's products will slow in light of diminishing [crime] concerns," and that "imports will satisfy a growing portion of domestic demand."
We basically have as many guns as people 
