Well, it's definitely possible to print a silencer, a pistol shouldn't be that much harder. I'm afraid that this would make the governments impose stricter laws on 3D printers, which is not a good thing...
I have downloaded complete plans that were created in 1972 to make an entire .22 caliber single shot pistol by hand using a hacksaw, file and drill press. By my estimation, it can be done in one long day of work by a semi-skilled person. An even simpler pistol can be built in an hour or two. It's just not hard to make a basic gun: when I was 11 years old I used to make toy "guns" from old hollow keys, crushed match heads and nails. They worked, but only had about a 10-foot or so range.
Granted, I planned to build the pistol using a (manual) milling machine, not by hand, but is the government going to outlaw saws and files now?
Yes, but the quality of a good 3D printed gun will be better and it's easier to download the blueprints and literally print them rather than understand and build the gun yourself.
I, too, used to stuff firecrackers down a pipe and shoot steel balls (from bearings) when I was a kid - it was fun, what can I say :-)...
A suppressor has no moving parts and serves only to baffle the expanding gas and reduce noise. It experiences relatively low heat and gas pressure. The components of a firearm have far tighter tolerances and must withstand significantly higher levels of pressure and heat. It's not even close to the same thing.
There is a whole hobby community of people who manufacture their own ammunition. You can order everything you need to get started over the internet, with no permits (unless you live in a short list of states like Massachusetts, in which case a firearms permit is needed to purchase ammunition components).
Some people do it to save money, some because they're competitive shooters (who want to hand-optimize their loads), and others are survivalist types who want to be "off-the-grid".
(I don't know if this is sarcasm, but I'm answering with the assumption it's not.)
Manufacturing ammunition is simple and requires components and equipment that can be purchased for relatively little money and with (almost) no restrictions.
Buying gunpowder, primers, bullets, and casings is very possible via the internet (though gunpowder and primers are subject to hazardous shipping restrictions). After that, you could in principle make ammo using a 2x4 and a hammer if you really wanted to. A single-stage reloading press and the accoutrements can be obtained for under $200 trivially, and if you want to step up to relatively fast manufacture (hundreds of rounds per hour) you're still only talking a $500ish investment.
