Let's say I get a barrel that does not have m4 barrel extension, but my upper has the feed ramps...can I add the barrel extension on the barrel?

Does this barrel have the m4 barrel extension if it doesnt advertise it?
www.del-ton.com/detail.aspx?ID=487

And what if I buy a barrel with the M4 extension...and a receiver with no m4 feedramps, can I take the extension off the barrel? Is that hard to do?

Changing barrel extensions is NOT a do-it-yourself project. Just get the right barrel to match the upper. If you have an M4 upper, get the M4 barrel. If you have a regular upper, get a regular barrel.

You can fit an M4 barrel on a standard receiver with few worries, but if you try to put a standard barrel on an M4 receiver you're risking BIG jamming problems.

Quoted: but if you try to put a standard barrel on an M4 receiver you're risking BIG jamming problems.

In theory that is true but I've got three uppers with feed ramps using barrels without the extended ramps and they have all been perfectly reliable.  The only way it could be a problem is if a magazine were out of spec in some way.

It is not that difficult to match the feedramps in the upper using the proper dremel tool.  One that is shaped like the tip of a bullet works excellent for me, I've done it dozens of times and not had one failure.  The only secret is to take a little at a time from the barrel extension until it matches, and don't go too high or too far back toward the chamber when cutting.  Common sense and a good pic of a M4 ramp will help.

I made the same modification to my extension feed ramps. I used a round file to start, then wrapped different grits of sandpaper around it till I got the contour I wanted. Work slowly and trial fit to the upper frequently. After I got the ramps where I wanted them I polished with a Dremel felt bob. The combination works flawlessly.

I've got 2 rifles with M4 feedramps.


I've found that the tip of the bullet never, ever hits the part of the ramp that is on the receiver. It always impacts the center of the ramps on the barrel extension. At first, that made me wonder what the point of the M4 feedramps were. I've cycled many rounds manually to see what happens. While cycling slowly and manually the extended area of the feedramps seems to contact with the shoulder of the cartridge sometimes. I am merely guessing as real recoil is much different than manual cycling, but I suppose that helps smoothen the feeding process. It allows the shoulder to pass without bumping the bottom of the ramp on some occasions.