So I have LOOKED AND LOOKED AND LOOKED AND LOOKED AND LOOKED and still cant find a list.  Someone started on in 2009 but there were no real options back then.  Hopping 4 years has changed things.  

What free float key mod rails or modular rails will fit over the Osprey 416 Piston Kit without modification to the hand guard or the piston rod?

There white paper says you need .90"+ over bore.  That would mean an ID of 1.8"....  There is nothing I can find in that size.  The JP Enterprises is 1.75" and that is one of the biggest I can find.  Anyone who has found a solution please post a reply with a link to the manufacturers product page so we can make a sticky worthy post.  I really like the Osprey Kit over the AA kit but the lack of being able to put a 13-15" hand guard on a 16" mid-length barrel is a deal breaker.

Links to confirmed handguards that work with the Osprey Piston System:

https://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_id=268

Seekins Precision MCSR Rails
Seekings Rail requires Osprey op rod
Seekins Precision MCSR Rails
Seekings Rail requires Osprey op rod


Links to UNCONFIRMED handguard options

Head Down Provectus 9", 13", 15" Keymod Rail

MI SS series first gen  will work

So would that be this one with the 1.75" ID?

https://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_id=268

Thank you for everyones response so far.  Lets keep it coming!

This is one I found that "SHOULD" fit but is not confirmed.  I say should because the ID is 1.8" and does have a little added room for the gas tube under top Pic Rail.  Can someone confirm?

Head Down Provectus in 9", 13", 15"

I prefer to make up lightweight Osprey ARs. I'm sure the AA products are OK. Free float tubes won't go over the AA. I usually take a 1/2" Dremel drum abrasive to the Osprey rod clip to level it to piston cavity top, about 1/64" or 1/32". Touch it with a black felt pen. The carbon fiber AP free float tubes slide over nicely with no interference. http://www.apcustomusa.com/standard.php

Bob

This sounds interesting, can you please post of pic of that mod?

I too would like to see a few pictures of the mod.  What is the ID of the Carbon Fiber Handguard you liked to?  What does the piston look like after you took a Dremel to it?