Can anyone with knowledge please give an explanation of the use or purpose of a piston. i did not do significant research but would like to be pointed in the right direction to learn about the benefits, if any, of mounting one. Basically, what is a piston or 3 lug adapter? I have an AAC EVO45 pending at the moment and I was just going to mount it on a threaded barrel. Is there a specific thread pattern required or would a piston be beneficial for this? Sorry if i sound extremely newbish but, i'm just trying to educate myself..Any info will be greatly appreciated.

The piston is a part for a LCD/LID device and needs to have the same thread pattern as your barrel.  The LCD/LID device helps certain semi-auto weapons (browning style actions IIRC) reliably cycle rounds.  It depends which weapon you run the suppressor on if you will need an LCD mount.  1911 might be ok with just a thread adapter, HK USP Tactical will probably need the LCD with correct thread pitch piston.  

A three lug attachment is used alot on MP5s and 9mm ARs.  The end of the barrel has 3 lugs machined into it so you can mount a suppressor or flash hider onto it.  The 3 lugs index and lock the muzzle attachment.  You probably won't need to worry about this.  For now.  

You will probably (99%) need an LCD/piston setup or a thread adapter setup for your pistol.  You will also need to find out what thread pitch the threading on your barrel has and also see if your pistol requires cycling assistance with an LCD (just tell us and someone will give you a good idea).

-X



I hope Polite Society won't mind me reposting the photo but you can see the LCD device with the piston (silver part).  I recommend Polite Society if you need to purchase anything BTW.  

Your evo has a piston in it.What thread pitch piston did you order your evo with? That is the pitch you need your barrel to be.

Thanks for the replies so far..it gives me at least a start in the research. I'll find out what thread pitch was sent later on today. The paperwork is still pending and when I initially ordered the EVO, I simply asked for a .45 caliber suppressor at the time. I was planning on using it with (2) different host's. One is the newer HK45 and the other is a 1911. I'll stop at the shop I deal with to get more detail. It's run by one of the site's staff members...