In 1911's there is a thing called a Vertical Impact Surface (VIS). It is where the lower barrel lugs contact the frame to stop the rearward movement of the barrel. There is a fair amount of stress on the lower lugs during this process, so some manufacturers in order to mitigate the effects of that stress use what is generally referred to as a "bow tie" cut. A portion of the VIS is relieved so that the only the upper portion of the lower barrel lugs contact the frame. It is called a "bow tie" cut because it leaves a shape resembling a bow tie at the top of the VIS. By doing this, the strongest part of the lower lug is bearing the load and it minimizes the amount of leverage the forces have on the lugs. If the lower part of the lugs contacts the frame not only is that the narrowest and weakest part of the lug, but also being the furthest away from the base of the barrel it creates greater stresses on the lug. Over time, with this increased stress, the lower lugs will shear away from the barrel or otherwise become damaged.
From my understanding, some models of the Remington R1 do not have a "bow tie" cut, or did not have a "bow tie" cut. There was also some issue of the bevel between the barrel bed and VIS that is supposed to provide clearance for where the lower lugs lie into the base of the barrel being too large. Which if a specific gun did not have a "bow tie" cut on the VIS would prevent one from being added because it removed too much of the upper half of the VIS.
My sample of 1 happens to have a "bow tie" cut and while the same type of bevel is there, it is not as large. I am not certain if this is a disparity between the base model R1 and the Enhanced version, or if there has been a production change. Rumors floating around the Internet are pretty inconsistent. Just be wary of older production R1's or base model R1's. They may or may not have a properly machined VIS.