Colt LE6921/M4LE lower and rLL

[Quarterbore]

Can you take some photos of the internals of your lower (obviously without the upper in the way)?

As for worying about a particular lower and using that with the link, that is really backwards almost as bad as buying tires and then looking for a car that fits them. Buy the rLL and if the Colt does not work, either modify the lower so it will work or buy a Bushmaster lower that will work without modification.