As mentioned earlier, the bullet tips SHOULD NOT be hitting the M4 feedramps on a regular basis. They are there to help chamber the rare round that feeds slightly low from a bad mag for example. If you are getting wear on your dremeled feed ramps, then you have some definite mag problems, and the same mags probably would jam a standard extensioned receiver. The M4 ramps are a slight improvement when feeding from bad, or dirty mags, and will chamber some of the rounds that would jam a normal rec/bbl ext(which doesn't happen very often). They are NOT there to feed every single round, so wear on that part is a mute point. Also, as mentioned earlier, the only real draw back to having demeled feed ramps, is chemical resistance/oxidation, which for most of us is a mute point as well.
Having said that, There are planty of good upper receivers out there with the ramps cut before they are anodized, so why not purchase one of those? Mine is a CMT upper with the ramps purchased from Denny, and i installed a CMMG barrel with the M4 extensions and they lined up beautifully. Best of both worls and for a great price.