It works without removing the ring. The only part that must be removed is the sling mount. The rail has a spot on each side for a quick release but I like using 550/parachute cord as an attachment.
.
Printable View
I've had a FDE VTAC Delta on my LE6920 for a couple of years. I've been very satisfied with mine. Fit and finish is excellent. I also have a Troy Delta rail on one of my BCM uppers. I really like it too. It's nice that I didn't have to modify anything to install them, and they lock down real solid.
http://i5.photobucket.com/albums/y19...psb68b4df0.jpg
http://i5.photobucket.com/albums/y19...ps9a47ea0a.jpg
A longer sight radius isn't a bad thing, but I do think it depends on your needs for the rifle. For me, the effort to cut down a front sight post or replace the front sight assembly with a low profile gas block just wasn't worth the effort or cost when I could keep what I had, and IMHO not really gain me anything.