bobthefisher
Durka ninja
This guy is still selling the cheap, tiny, direct-thread, full-auto rated Gemtech TREKs for $295 on GB (see below). I got one, and I must admit they sound really good, on par with my SilencerCo Specwar 556. I'm a big SilencerCo fanboy due to their customer service, so if you only want the suppressor for .20 cal projectiles I'd stick with the Specwar or Saker, but I hear the .30 cal Omega sounds really good with the replaceable .20 cal end-cap. You're going to want a company with excellent customer service, as full-auto fire is really hard on the blast baffle and may eventually need to be re-welded. SilencerCo would do that for free the first time.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=538180145
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=538180145