I recently purchased 2 AR15.COM lower receiver, and is currently deciding to duplicate both my 14.5" and 16" DI with piston version of both.
Both my DIs have rifle length DD rails, with the gas block inside the rail.

I am searching for mid-length piston systems that can fit under quad rail, and needed suggestions.
So far, the only one I find is the Osprey Defense, but have not been able to get much information about the system.

Thanks in advance.

Syrac Ordnance now makes a low-profile adjustable-gas piston system. It would probably work.

I haven't heard anything good about Osprey piston systems. After a lot of research, I chose Adams Arms with the Evolution EX rail. I believe Syrac is sort of their R&D department, so definitely worth looking into.

What?!  That is completely wrong.  Adams Arms and Syrac have no professional relationship that I know of.  Syrac was founded by the founder of AA (after he left AA) and that's pretty much where the relationship ends.  Facts man, get them straight.

And back on point... the AA XLP (as in eXtra Low Profile) sits pretty low and the MI SS Gen II FFHGs go right over them without issue.  Should play nice with others as well.

So far, Syrac Ordnance and Adam Arms XLR.
Is there any photos / drawings that compare the two gas / piston blocks, and have a review with the Syrac Ordnance system?

The Samson Evolutions series is what Adams Arms uses on some piston rifles.

I have a Syrac on order for just that reason. Will I ever get it....? 3 weeks wait already..!
I think an Osprey would work... Not positive. Not in hand yet. Only have AA and it will not fit with out issues.

I have 3 osprey systems in half of my 6 ARs...they work flawless and reliable they had some heat treat problems when they first came out but thats been long ago resolved...they drop in in 10 minutes no permanent mods...no vlves,no springs no screws used a metered gas system the gas chamber only takes a certain amount of gas to cycle it so any ammo will run in it..it self adjusts and more importantly no I repeat no carrier tilt and gouging like ive seen in AA kits and the ruger SR556 osprey makes em carbine,mid and full size I run em on 14.5/phantom 5C1 barrels with an H3 buffer great reliable system.5 years ago I had the gas cyclinder come loos from its spigot osprey took care of it imediately funny thing was it kept functioning even loose until the part was replaced I dont know of any piston rod system thats done that functioning while broken...in any event over 32,000 rounds of all types of ammo spread over 3 rifles in the last 4 years no problems very reliable.Magpul piston handguards work great with heat shield mod so it doesnt contact the piston cup and mid west industries makes a rail for it

Osprey, is that you?

Find and show me some recent carrier tilt in an AA system?  I'll be waiting patiently...

Not sure why someone would post they'd never found a good review of Osprey systems. They clearly haven't looked here.

I've been running Osprey kits on two ARs for several years. I trust them so much that I just put another one on my .300 AAC Blackout build.

Customer services at Osprey is beyond reproach. I have contacted them several times to get parts to swap barrels and FSPs and they have been excellent to work with. Joe is a class act. Easy to talk with and knows these systems inside and out.

Don't hesitate to look seriously at Osprey Defense.

I am open to any manufacturer, as long as they can resides under a quad rail system, my preference are Daniel Defense Omega X, or Lite Rail 3, or RIS 2.

I have seen some reviews with ADAMS ARMS XLP, but have yet got confirmation with how it works with the above rail.  

I have not seen much review from Syrac or Osprey.  I understood, Syrac is relatively new.
Looks like, for Osprey, I need to remove the rail for any maintenance, service, or cleaning.

Give both AA & Osprey a call and ask.  Their both super nice and helpfull

I tried both, seems like they much prefer email.  I dropped them both email, awaiting answers.
Oh well, maybe I'll visit their booth during the Shot Show.