of the several hundred feed ramps on 1911a1's i've done, i've always used the cratex abrasive rubber bullet shaped bits. they come in different grits and as powder burns said, you do not have to eliminate the lines. and when you're done,
push the barrel back and insure a gap of about 1/2 dimes width ( hi-tech). then with dummy rounds in your mag insure that as the breech face strikes the cartridge and starts to shove it into the chamber it allows the cartridge to point up slightly, not driving squarely into the feed ramp, more like begging to go in the chamber throat. this may require opening up the last 1/4 inch of the mags feed lips. then radius the bottom cut of the extractor, tighten the disconnector port to eliminate foreward and backward timing delays.
sorry, got kinda long winded.... good luck. always check it is unloaded when working on it.