FRP is First Round Pop which is when the first round is fired there is regular air inside the suppressor = 20% oxygen and when that oxygen is burned it adds a noticeable POP to to the first round fired. The next round(s) if fired closely behind the first round will USUALLY be significantly quieter because the O2 is gone from the suppressor. High end manufacturers have gone to great lengths to reduce or eliminate FRP. Lower tier manufacturers don't have the money to chase that science. It IS science.
Those $400 and $500 suppressors are NOT overpriced for what you get and it IS rocket science. I've dropped some coin and I know. I researched diligently for 3 years before I spent my first NFA dollar.
All you could ever want to learn is here......
http://www.silencertalk.com/forum/index.php?sid=ca2d051b5178942a32d8f6f40cc763adAt any rate, I sincerely hope that you are 100% satisfied with your suppressor once the ATF sends the approved Form 4 and you take possession. The NFA game is rarely over with just 1 purchase though
