[shaggy]

During the later part of the Vietnam War, Colt introduced the XM177, an M16 with collapsing stock and 11.5" barrel. A long flash-hider with an expansion chamber took an unbearably loud rifle and lowered it to regular rifle volume. In the 1970's, BATF (in their infinite wisdom) classified it a "sound suppressor", based on the amount of decibels it reduced the sound. Never mind the fact that the rifle still sounded like a rifle.

You have to be careful with the "sound lessen'ors", too.

This is absolutely correct. The XM177 moderator was found to only reduce the sound by about 1-2 decibels (and for a general frame of reference I think a 20" barreled M16 produces something around 160 decibels). BATF still found this amount of sound reduction sufficient to regulate the moderator as a silencer/suppressor.

1. is Origon a Class 3???

I believe so.

2. Can you buy the parts to make a supressor mainly i'm just thinking of the barrel *if thats applicaple* i'm not excatly sure how a supressor is made but i will voice my thoughts lower...

As far as I'm aware, you cannot but a suppressor "parts kit" and assemble it yourself. You can get a threaded barrel, but thats about it. BATF/NFA had a long standing rule that suppressor parts were to be regulated as complete suppressors. This stemmed from the statutory definition of a "Silencer" in the US Code:

18 USC 921 (a)(24) The terms “firearm silencer” and “firearm muffler” mean any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication.

I've heard rumors BATF/NFA has relaxed this rule, but I've not seen anything to verify it. This was much more of a problem years ago when suppressor designs were mostly made with disposable rubber "wipes". Instead of a metal baffle stack, there would be a series of round rubber discs inside the "can". The first bullet would cut a hole through the wipes and the successive rounds would follow. The wipes would act sort of as a curtain that would 'close' somewhat after each round went through, thus slowing and containing the gasses. Problem was, those wipes would quickly wear out after a couple dozen rounds went through and the sound levels would quickly rise after that. Then you needed to either make a new set of wipes (you couldn't have spare wipes laying around as that would constitute another suppressor) or you needed to send the can out to a licensed manufacturer to replace the wipes. A real PITA. Fortunately we're long past that stage of suppressor development and most are now made with a permanent metal baffle stack.

3. does the class 1 form allow you to buy silancers after the fact??

Nope, you have to file a new form 1 for each suppressor you want to make, or another form 4 for each one you want to buy...and that includes an additional $200 tax for each. If you ever get tired of it and want to sell it, there is yet another $200 tax due to transfer the suppressor to a new owner.