What is an M4 feed ramp?

[S.B.]

Here are pictures http://s557.photobucket.com/user/gat...ps2-1.jpg.html

from http://www.thehighroad.org/archive/i.../t-765115.html

Basically the rifle feed ramps are on the barrel only and the M4 ramps continue into the receiver. The photo shows the different combinations the acceptable comfigurations.

So, you're saying proper machining is the key?
Steve