I'M looking at getting a sound suppressor for a Ar-15 I have yet to own ( plan on building one) is one brand better then another? Can you buy a class 3 full auto lower? Or do you have to buy the whole class 3 gun? How does the whole class 3 system work? I know you have to buy the item and then send in the 200 tax stamp per item and then wait 90 days for it to come back from the ATF. But what if your turned down by the ATF can you get your money back for the items? I don't really want to drop close to 2k on items and paper work fee's just to lose it all. My long term goal is to put a PVS-14 night vision scope on the rifle and mount a PEQ IR laser and IR illuminate. Thanks for the information.