I don't have a lot of experience with free float rails.  The Ruger Troy rail is supposed to be pinned on.  I see three pins... see the picture and schematic

1. The huge lower roll pin seems too low and to far from the receiver to be pinning the rail to the receiver... am I missing something?
2. The two small pins at the top seem too small to be providing such rock solid feel... also they maybe see to be for holding the guide bushing for the operating rod in place....

Anybody have an idea about what holds the Troy rail so solidly in place?  Is is threaded on the receiver?  Is the weird barrel nut holding it?  I can't quite figure it out....

See part 72? This is the bushing for the rear of the transfer rod. It has 2 crossways grooves in it that pins 66 (in the handguard) and 46 (in the upper) engage. It also clocks the handguard to the upper and the pins hold it in place.

Pins 66 and 52 keep the handguard from sliding off. The barrel nut is really long and the handguard fits tight to it so there are a couple of things working to make the handguard a stiffy.

I wish the spirol roll pins (items 46, 52, 66) were solid. That would be nice.

Thanks... but... pin 46 ??  That's in the bolt carrier, the firing pin retainer pin..... which did you mean, it can't be 46 ?

Yes it is 46. It is the lower pin. There is no break down for the BCG.. The 46 groove is most likely in the barrel nut.

Here's a lame edit of your handguard picture. The transfer rod bushing (72) that bridges the upper and rear of the handguard is sketched in even lamer broken lines.

Ok, I think you misread the drawing... Both small pins are numbered 66.... Neither of them is 46

The numbers R too small. I think you are right.

Looks like the rail is a variant of the new Troy TRX Standard Battle rail.  The Troy TRX Standard (still hasn't shipped yet, maybe because of supplying Ruger?) from the latest news seems to use a custom barrel NUT, NOT like the one in the Ruger Drawing, more like the original barrel nut, and it has a allen head screw where the large drift pin is on the Ruger Rail, to clamp the rail unto the barrel nut.

Pin 32 appears to go through the rail and the piston block, look at the pictures of the gas block on the other thread about the Ruger, you see that pin in the front top of the rail.

Looks like they changed it to use a different barrel nut to pin the Rail at the barrel nut, the bushing for the piston rod at the receiver and rail and at the piston block.  I'm guessing it helps support the piston and rod as well during its action.  So I guess, technically its NOT truly a Free Float Rail, but at the same time, if the extra support helps the piston action to be more reliable, that is probably more valuable than what free floating the rail will ever get you.

Is the rail pinned and the only way to remove the rail is to unpinned it?  

I normally wipe CLP protector on the outside of the rifle if I don't intend to shoot it for awhile so it wouldn't rust. Heat will strip that CLP away after a few houndred rounds. Also heat will create moisture around the barrel so rust could accelerate if left untreated. Looks like it's going to be a PITA just getting to the barrel.