I wouldn't worry too much about whether the silencer kit/solvent trap will be declared illegal in the future by BATFE. Your investment is about $350 total. Form 1 it; build it; shoot the heck out of it - you will have gotten your money's worth and had some fun for under $400. You will also know if you really want to invest in a real silencer or not and have a lot more working knowledge to evaluate your next one. So, if/when BATFE comes a knockin; show them your form 1 and then just hand it over and say "thanks".
I dont want anybody to misunderstand, im not trying to just be a jerk about it. What many may not realize is that atf may not even know these are being sold. The company may not have sent a kit in for approval. So, at some point, atf does discover the kit, and then makes a decision. The one they would have made earlier if given the chance, and the seller could have made suggested changes to fix it.
An example. Probably 10yrs ago now, some importer wanted to import a bunch of cut up submachine guns as parts kits. Now, as most of you probably know, this is done all the time, and is legal. However, atf does have a specified way that the receiver must be destroyed. The importer assured them it would be correct, and got the permission. I think something like 8000 kits came in. At customs, atf never looked at any of them, just figured they were gtg. The importer sells them, almost all to a well known parts and surplus seller.
One day, a strange machinegun turns up at a crime scene, and atf is called. Why, its one of these kit guns. Instead of the normal torch cutting of the receiver we are used to, it was just bandsaw cut. Somebody got the kit, and an hour with a welder, and he had a machinegun.
Atf immediately declared all kits contraband, and set about aquiring them. Now, all they really wanted was the receiver sections, but they got most of the whole kits, about 5000 of them. The distributor i mentioned? Lost their entire inventory of them, just had to eat it. The importer? Closed and disappeared. Basically as i described, they found out you had purchased one, they just showed up and said it was illegal, hand it over. I personally know someone who lost one this way.
I spent 3hrs one day talking with the agent who was in charge of this whole thing.
So, really, my whole point was that atf may not know about it, and at some point could or will find out, and may decide its gone too far. It may never happen. The company may have already gotten it approved, although most times companies do point that out, so i doubt it.
Would you go to jail? Not unless you refuse to give it up.
Its just that i would hate to lose that kind of money, i think $400 or so was mentioned, over something so easily avoided. Thats all.