Here's the deal folks...
Think of it as there being two levels of C3 ownership - that as a dealer/manufacturer and that as a regular, John Q. Citizen. If you're going to be a dealer/manufacturer you can get a wider variety of weapons (more on that later), but there is more paperwork involved, annual fees, possible BATFE inspections, and a legal requirement to actually do business. If you just get a license to enhance your own personal firearms collection, BATF can pull your license and possibly bring charges of tax evasion. Unless you really have police contacts and/or the capital and desire to sell to the public, do not get a dealers/manufacturers license.
As a regular John Q Citizen, you can purchase a number of machineguns, suppressors, Any Oher Weapons (AOWs), Short Barreled Rifles/Shotguns (SBR/SBS), and Destructive Devices (DD). Of those six categories machineguns are is the only one where there s a limitation on what you can buy. On May 19, 1986 the Firearms Owners Protection Act was enacted which although containing some good measures for fun owners, also carried a provision to ban the sale of machineguns manufactured after that date to civilians. Thus if you want a machinegun, it has tobe one that was made and properly registered prior to May 19, 1986. This date restriction does not apply to dealers/manufacturers, but again, there is a lot more paperwork, fees, liabilities, and legal requirements for a dealer/manufacturer's license.
Of the five categories of NFA weapons other than machineguns you (as a regular Joe, non-licensee, non-dealer/manufacturer) can buy the latest, most up to date things. In common parlance, machineguns eligible for civilian possession are known as "transferables".
There are also machineguns known as "pre-86 samples" and post-86 samples. These two terms deal with machineguns made before and after the May 19 cutoff date, neither of which is eligible for civilian possession based upon the date of the manufacture (after the May 19 cutoff date) or their importation (after the 1968 GCA).
Thus, you can see why as a regular citizen you can own an M16, but not a P90 - its all about the date of manufacture and importation, and the law (18 USC 922(o)). For example, there are many M16's which you can buy as an individual, but you cannot buy a P90 or G36. You can buy an MG42 but not an MG3. There are converted HK94s and a very few factory MP5's, but no UMP's for civilians. Just remember, for it to be available to John Q. Citizen, it had to be made AND properly registered prior to May 19, 1986.
The process is relatively easy, although a little difficult to understand at first, and long. YOu can make any NFA wepon on your own (except machineguns) by completing a BATF/NFA form 1. You can also buy any NFA weapon (including transferable machineguns) from a dealer in your state or an individual in your state by completing a form 4. Both the form 1 and the form 4 are available to download at
www.titleii.com
You'll need to complete TWO copies of the applicable form, ONE copy of a US Citizenship certification (also available on
www.titleii.com), TWO FBI fingerprint cards (available through BATF/NFA), and a check for the proper transfer or making tax ($200 for all cases, except the transfer of an AOW which is $5). When completing the form 1 or form 4, you'll have to go to your sheriff, chief of police, or district attorney to get a "sign-off" on the forms, so you should call and see if someone there wil sign the forms for you. Its basically a certification for them, that says they have no reason to believe you'll use the weapon in an illegal manner, or your possession would be in violation of the law. Please note, this official has to have jurisdiction in your county, city or municipality. They cannot be from the next county, and it has to be she sheriff, DA, etc who signs the forms - NOT a secretary, assistant, or the deputy unless they have a specific grant of authority to do so. If they do not sign (and there is no legal requirement for them to do so - it is completely discretionary) there are ways around it, but it gets more expensive and complicated - basically you need to form a corporation.
Assuming they'll sign, however, you get both copies ofthe form 1 or 4, both firgerprint cars, the citizenship certification, and the tax check, and send it all to BATF/NFA. In about 3-4 months, either you or your dealer will get back ONE copy of the approved form 4 or form 1 (F4 goes to the seller, F1 goes to you). At that point, you can begin to make your NFA weapon (if on a form 1) or take possession of your NFA weapon (if on a F4).