I purchased a full length magazine tube from CarrierComp, a titanium tube, for my M4 Benelli and installed it yesterday. With the right tools, and with enough patience, doing it was quite straightforward. But you have to get over the fear that you are going to ruin your receiver when you start blasting away with the heat gun. In fact, unless/until smoke starts to come out, you have not heated it up enough.
Hope some may find this video useful if they decide to install a full length magazine tube for themselves. LINK TO VIDEO HERE.
I can't say enough good things about the quality of CarrierComp products, the fit and finish are truly superb. Great folks, Kip and Marcy, own/operate the business.