What is an M4 feed ramp?

[PhillipM]

How is it different?

[gwp]

Here are pictures http://s557.photobucket.com/user/gatorhunt2201/media/AR15%20stuff/feedramps2-1.jpg.html

from http://www.thehighroad.org/archive/index.php/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.

[PhillipM]

Thanks.

Why were the M4 ramps developed?

[gwp]

I believe the M4 ramps were developed to correct feeding problems when firing auto. Apparently as originally designed the movement of bolt/carrier of the M4 was much more severe than in the rifle. Occasionally, when firing full auto, the cartridge tip would hit the receiver under the feed ramps causing a stoppage.

[BigMo]

Yes- there were issues with the short gas system providing gas at a much higher pressure than a rifle. That increased the carrier speed, which the magazine wasn't designed for. So at times the cartridge wasn't in the proper place when the bolt tried to strip it from the mag.

Something like that.

Taking the gas system from a rifle length to a carbine length opened a can-o-worms. Most of it has been hashed out. That is why some prefer the "mid-length" gas system. Shorter than the rifle but less issues than the carbine length.

[PhillipM]

Thanks.

I guess a smaller orifice or tube wouldn't fix it?

[gwp]

Thanks.

I guess a smaller orifice or tube wouldn't fix it?

There are a lot of things that Colt could have done, but the M4 ramps were probably a quick cheap fix that did not require a lot of engineering or development. Now with many shops making AR parts that are not manufactured to the military drawings, there is a wide variety of specialty parts with designs and processes believed to maximize the function of the AR.

[barretcreek]

Thanks for asking the question about the ramp configuration Phillip.

[albert]

I thought the longer 70 gr bullet had something to do with the feed ramp revision.

[Chris W.]

After looking at the M4 ramp pics, wonder if you could modify a standard barrel ramp and upper into a M4 with just a dremel and a small stone ?? Doesn't look to hard to do, nothing looks to critical either. Anyone tried it ??
Chris

[S.B.]

Here are pictures http://s557.photobucket.com/user/gatorhunt2201/media/AR15%20stuff/feedramps2-1.jpg.html

from http://www.thehighroad.org/archive/index.php/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