Problem with M4 ramps

[ncgunner]

I am building my first AR based on a Satern match barrel in 264 LBC and a Mega Arms Billet upper. There is a ledge where the ramps in the barrel extension meet up with the ramp extensions in the upper. Mega tells me this is not any problem and ammo will feed fine. The retailer I bought the upper from says that it is normal to have to dremel ramps in a barrel extension to get them to mate up properly. See the attached image below -

Satern 264 and Mega Billet upper.jpg

Any help or advice would be appreciated. I am putting too much cash into this build to have anything other than perfect.

Thanks!

[CPT.CRAZY]

I cant tell for sure from the pic but it looks like your barrel extension is a rifle style not an m4. With m4 ramps in your receiver this will cause feed problems, the billet tip will snag on the lip. Some dremil work will be needed, or have the extension changed to a m4.

[RangerRick]

Hi NCGunner,

Here is a link to some photos to compare: http://www.ar15.com/archive/topic.ht...f=118&t=511200

Yours looks a little odd on both the extension and the receiver. Dremeling the aluminum of the receiver is easy. Doing it to the steel in the extension is another matter altogether.

I'd suggest seeing if it will hand feed from a mag. I'd also check with Satern to see if it is a rifle extension. If so you need a receiver with no ramps (rifle receiver).

RR

[LRRPF52]

There is no need to Dremel the upper receiver and strip it of its protective hard anodizing on this particular configuration. It does look like a rifle barrel extension in the picture, not an M4 extension. You can even see on the sides of the feed ramps how they don't mate up with the feed ramps on the upper.

Here is one that I blended:

http://www.65grendel.com/forum/showthread.php?1386-Templar-Customs-Digital-Desert-Cerakote&highlight=templar+customs+desert+cerakote

Your barrel is already chambered with that extension, so you don't want to remove it. It just needs to be blended carefully by someone with patience and knowledge of how the feed ramp angle needs to be maintained.

[Drifter]

Not uncommon to encounter feed ramps not matching up perfectly. Sometimes it can pose problems, and other times it doesn't.

Feed ramps are not difficult to blend with careful use of a Dremel using an appropriate tip.

If you're not comfortable doing it yourself, it's not too costly to get it done professionally:

http://www.adcofirearms.com/shopservices/shop_.cfm?code=5

[ncgunner]

Problem with M4 ramps

Hi NCGunner,

Here is a link to some photos to compare: http://www.ar15.com/archive/topic.ht...f=118&t=511200

Yours looks a little odd on both the extension and the receiver. Dremeling the aluminum of the receiver is easy. Doing it to the steel in the extension is another matter altogether.

I'd suggest seeing if it will hand feed from a mag. I'd also check with Satern to see if it is a rifle extension. If so you need a receiver with no ramps (rifle receiver).

RR

They are M4 ramps in the barrel. I have confirmed that with Satern. And looking at the barrel extension outside of the upper, it is obvious they are M4 ramps.

Looking at the ramp extensions in the upper, they seem to end higher up in the vertical face than other pictures I have seen. So, I am wondering if the angle is cut wrong - not as steep as it should be? I don't have any way to accurately measure the angle.

Thanks!

[kamrr4437]

i dont think what you have there is going to cause a lick of problem. Its definately M4 feed ramps because it is machined all the way out to the bottom edge. If it were rifle it wouldnt be, it would stop prior.

[Whelenon]

There is no need to Dremel the upper receiver and strip it of its protective hard anodizing on this particular configuration. It does look like a rifle barrel extension in the picture, not an M4 extension. You can even see on the sides of the feed ramps how they don't mate up with the feed ramps on the upper.

Here is one that I blended:

http://www.65grendel.com/forum/showthread.php?1386-Templar-Customs-Digital-Desert-Cerakote&highlight=templar+customs+desert+cerakote

Your barrel is already chambered with that extension, so you don't want to remove it. It just needs to be blended carefully by someone with patience and knowledge of how the feed ramp angle needs to be maintained.

LR is right on, I would not touch the receiver and only blend the barrel extension. You want to eliminate the sharp edge between the barrel ext. and receiver.

[LRRPF52]

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.

[bwaites]

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.

[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?