Problem with M4 ramps

[ncgunner]

If they are properly cut feed ramps, there should be no flat spot on the bottom edge, it should be almost sharp, like LRRPF52's picture. It looks to me that there is a flat are, but as LRRPF52 notes, the area is out of focus.

There is a slight flat at the bottom edge of the ramps in the extension. With the barrel removed from the upper, the flats are difficult to see. But, they stand out easily when assembled in the upper.

Looking at LRRPF52's photo, it would appear that my ramps are not cut as deep by a couple thousandths. I am judging this by the amount the M4 ramps "notch" through the barrel extension on the bottom edge. So. I guess my I'll just need to do a little hand work to the extension.

Thanks!

And, thanks to all others for the help!

[LRRPF52]

If you do the Dremel work yourself, just be patient and measure often. Use the green conical earplug shaped polishing tips that have a slight abrasive in them, not anything aggressive. Just a little at a time, slip it in the upper and check for fit, remove, polish, check-fit, repeat until happy.

[ncgunner]

If you do the Dremel work yourself, just be patient and measure often. Use the green conical earplug shaped polishing tips that have a slight abrasive in them, not anything aggressive. Just a little at a time, slip it in the upper and check for fit, remove, polish, check-fit, repeat until happy.

Thanks for the advice. Well taken. It will be a couple months before I can afford the rest of the parts I need to finish this out, so I'm plenty patient. :-)

The green conical polishing tips you refer to - are these dremel brand? Do you know a good online source?

[LRRPF52]

I use the Ryobi green polishing tips. I'm not sure what color the Dremel brand are, but maybe someone will pipe in and let us know.

Also, let us know what parts you need, and some of us might have them laying around.

[txgunner00]

It's kinda hard to see that area since it's out of focus. The thing I like to do is a "meltdown" so the extension doesn't scratch the crap out of the projectiles as they feed past the cuts for the 5 o'clock and 7 o'clock bolt lugs. I take the edge off the bottom center of the extension between the feed ramps, and do a general blending of all the sharp edges.

Can you describe your meltdown process?

[LRRPF52]

I take the edges off every area of contact where the brass touches during feeding. It's meant to ease feeding, and baby your brass as much as possible. A barrel extension basically comes as a machined part with no attention to detail other than being properly head-spaced. This is an extra touch I learned from a gunsmith who specializes in AR's. He does it on -15's and AR10's.

If you look at the picture, you can see how the sharp edges are smoothed out. It's the same idea behind polishing a 1911 feed ramp, and "throating" the chamber. The term "meltdown" is usually used when taking off all the edges of a 1911 slide for a carry gun, especially up at the end of the slide around the muzzle, so it re-holsters and rides without digging into your hips.

[CBronson]

My Satern barrel has the same issue with my Mega billet upper. Haven't finished the build yet so I can't say whether or not it causes feed issues.

[madcritter]

Hi, new member, was looking for problem solving solutions for feed problems when I check on the forum. I was having some feed problems today while zeroing scope on my recent build. I see I have some light dremeling and polishing to do.Last few rounds in a couple different mags were stopped at the bottom of the of the feed ramp.

[sneaky one]

Yikes,,, always check in slow motion ( before dremeling )-to see where the bullet tip hits the feed ramp- make sure it's at least in the center,on the horizontal plane-and well centered side to side also- don't let a round chamber -- let the charge handle down slowwwlly, get an extra eyeball to watch where it contacts, sometimes it's just a mag. lip tweak upward to fix all woes. I've had to do this on all my junky mags.= cproducts grendel mags. from hell. Investigate all angles, contact points-wear spots etc. -before grinding on the rifle, thats a last resort! OMG!

[madcritter]

tweaked both mags at the range yesterday and it helped some. This morning I did a light dremel and polish of the feed ramp and now there are no feed problems with either mag.