I wouldn't spend money on a new barrel just yet.... I only mentioned the things to watch for on 'new' feed ramps because there are a lot of people with dremels... If you notice, the M4 ramps on almost all OEM guns are shiny silver- so it's obvious they aren't anodized either BUT they are made with a standard placement, angle, width and depth - we don't know if that is the case with yours as we don't know who did them. Also if the upper/lower are original to each other, they are designed either to have ramps or not to have them so if you had ramps cut, the should have been made as one unit on both the upper and lower for a smooth transition. If there are any 'ledges' for a bullet to catch on , well.... back to the drawing board.
You also don't need to buy a new BCG either- if you really need to, you can swap the bolt. The extractor comes off pretty easy with just one pin (hold it in good with your thumb and don't loose the spring). Replace the spring with an extra power and a rubber insert or o-ring. Also look at the extractor "hook" where it grabs the rim- make sure there isn't any build up of grime or burrs... test fit it to a case and if needed hand file for a good solid fit. (you can always replace this part cheap if needed).
Since the bolt is going back far enough to pick up another round, look to see what is preventing the fired round from being ejected (your ejector [round protrusion on left side of bolt face) works and has spring tension... right?) - you may have to work the action wit DUMMY rounds to see where the hangup is.
