I've seen plenty of references to "m4 feed ramps".  What's prior to m4 ramps?  AR-15 ramps?  M16 ramps?  

What's the difference between m4 feed ramps and everything prior?  Do they only have an effect on loading effectiveness during FA operation?  If so, then who gives a rat's ass if their rifle has m4 ramps or not, unless I'm the only guy on this forum that doesn't have a house full of class 3 rifles?

www.ar15.com/forums/topic.html?b=3&f=118&t=191733

Quoted: If so, then who gives a rat's ass if their rifle has m4 ramps or not, unless I'm the only guy on this forum that doesn't have a house full of class 3 rifles?

Well stated!

They affect [improve] feeding anytime bullets go from the magazine to the chamber.  

On earlier guns, feed ramps were not as deeply cut into the barrel extension, and not at all into the upper receiver.  On an early gun, with a full magazine inserted, directly in front of the tips of the bullets was a flat portion of the upper receiver.  Sometimes, during feeding, when the bolt strips the bullet off of the mag, the bullet may plow into the 'flat', instead of going up the ramp into the chamber.  This equals a stoppage, and usually a bullet with the projectile jammed down into the case.  Certain bullet types were much more prone to this type of malfunction.

With 'M4' type feed ramps, the bullets are lined up with the feed ramps while still in the magazine.  As they are stripped from the magazine by the bolt they feed directly onto these extended feed ramps.  This greatly improves the reliability of feeding, especially with certain types of bullets (soft nose, hollow point, etc).

Progress, man.  Go with it.