Finally installed the 13" Troy Alpha rail on. It is now "Free float " as I had to open up the top of the handguard where the gas block just touches (like the factory handguard). Will find out if this helps to improve consistency of groups....
Factory barrel nut is 4 oz and the rail is 7 oz
Troy barrel nut is 1.5 oz and the rail is 10.5 oz
Didn't add much weight in the end, 7 lb 3 oz without optics. I can still access the piston area just like the factory handguard but from the top lol. If i have time I might open up the front portion too.
With the rail cover removed
- got the rail on clearance for $100 all in. No way I'd work on anything more expensive lol
- had to trim off the one anti rotation pin on the left side of the rail, 1 minute
- trimmed off 2 tabs on the standard AR barrel nut so that the gas piston spring clears the nut, 5 mins
- opened up the top about 8 rail slots. 3 hours
- put on 2 coats of engine enamel on any bare metal surface
- put rail cover on opened top section to prevent fingers touching the gas block