M4 feed ramps or not? (w/ pics)

Frens · #1 11-23-10, 15:06

Hi guys,
I decided to replace the A2 upper on my factory MT6601 (20'' 1/7 Colt barrel mfg 04/00) with a flat top one so I started looking for a receiver w/o M4 ramps... while I was cleaning both my Colt today I noticed that the barrel extension's cuts on my 6601 look very similar to the M4 extension on my 6731 upper..
the barrel extension on the 6601 is not marked with a "4" like the 6731 but that look like a M4 barrel extension on a rifle receiver to me....

6601

6731

what do you think? do I need new glasses?

M4 receivers are easier to find so if that's really a M4 extension it would make my research a lot simpler.

thanks in advance
Frens

fdxpilot · #2 11-23-10, 15:22

Doesn't look like M4 feedramps to me.

mvician · #3 11-23-10, 15:29

Your 6601-NO, M4 ramps
Your 6731-YES, M4 ramps

chadbag · #4 11-23-10, 15:39

Quote:

Originally Posted by fdxpilot

Doesn't look like M4 feedramps to me.

???

It most certainly does? The "ramp" goes below the upper into the lower. Maybe not the best looking ones though.

Frens · #5 11-23-10, 15:49

Quote:

Originally Posted by mvician

Your 6601-NO, M4 ramps
Your 6731-YES, M4 ramps

just realized that maybe I was not clear in the first post and used the wrong words...just to make sure I'll ask again

I know my 6601 receiver doesnt have M4 ramps, but what about the barrel extension? doesnt it look like a M4 BE?

TIA
Frens

chadbag · #6 11-23-10, 15:51

Quote:

Originally Posted by Frens

just realized that maybe I was not clear in the first post and used the wrong words...just to make sure I'll ask again

I know my 6601 receiver doesnt have M4 ramps, but what about the RE? doesnt it look like a M4 RE?

TIA
Frens

No. Based on the right most picture you have for that one I would say no. Notice how the arc of the bottom of the feedramp swings in. It would be straight down and probably create a ledge with the lower if it were M4 feedramps.

.45fmjoe · #7 11-23-10, 15:51

You mean the barrel extension? RE means receiver extension which is colloquially referred to as the buffer tube.

Frens · #8 11-23-10, 15:54

Quote:

Originally Posted by .45fmjoe

You mean the barrel extension? RE means receiver extension which is colloquially referred to as the buffer tube.

wow I need to sleep... I'm going to edit the posts

Felix · #9 11-23-10, 15:58

Its pretty tough to say.

To me it looks like the 6601 does indeed have M4 feedramps on the barrel extension.

When you feel it, is the ramp recessed or is it flush with the perimeter of the barrel extension?

I'd hate for you to buy a new upper receiver and realize they aren't M4's after all. (Though returning it or having the extension ground down are options)

Any way you can install the barrel on your 6731 receiver?

.45fmjoe · #10 11-23-10, 16:00

Quote:

Originally Posted by Frens

wow I need to sleep... I'm going to edit the posts

I know the feeling, I tried installing a Daniel Defense LITE 12.0 FSP rail at 1:30 AM after working a full-time shift and then going to a police academy class at night. I called Joe Marler at DD the next day at work to ask him for ideas since the locking collar wouldn't rotate and I couldn't align the rails. Then I went home that night after class and lo and behold the fucking collar rotated just fine. I lined the rails up using a LT mount and tightened the bolts. I felt sheepish.

chadbag · #11 11-23-10, 16:01

Looking at both the middle and the right pictures I would say definitely not. The BE does not have M4 ramps cut in it.

Frens · #12 11-23-10, 16:07

Quote:

Originally Posted by Felix

Its pretty tough to say.

To me it looks like the 6601 does indeed have M4 feedramps on the barrel extension.

When you feel it, is the ramp recessed or is it flush with the perimeter of the barrel extension?

no it's not flush

Quote:

Originally Posted by Felix

I'd hate for you to buy a new upper receiver and realize they aren't M4's after all. (Though returning it or having the extension ground down are options)

If I'm not 100% sure I'll look for a receiver w/o the cut even if it'll take time

Quote:

Originally Posted by Felix

Any way you can install the barrel on your 6731 receiver?

didnt try that yet. I was hoping to find an answer here without messing with the guns

scottryan · #13 11-23-10, 16:32

That 6601 does not have M4 ramps on the extension. Your third picture shows this clearly.

Frens · #14 11-23-10, 17:17

thank You for your help guys.
I appreciate it

aspiderfreak · #15 11-23-10, 17:34

Here's an image I've found helpful in the past.

Hope it is useful to you as well.

ursus.peracto · #16 11-23-10, 22:09

This is the thread that expalins exactly what you need to know:

http://www.m4carbine.net/showthread.php?t=193

fdxpilot · #17 11-24-10, 15:20

Quote:

Originally Posted by chadbag

???

It most certainly does? The "ramp" goes below the upper into the lower. Maybe not the best looking ones though.

Well, perhaps I wasn't clear. The picture I posted was of a proper M4 feedramp, which his 6601 does not have. I was looking for the picture from AR15barrels.com, but couldn't find it with a quick search, so I used one from a previous "M4 feedramp" thread here, which is referenced in the thread immediately above this.

4thPointOfContact · #18 11-25-10, 20:00

The question I would ask myself is ....

"Do I need the feed ramps that had to be developed to make the M4 feed reliably like the feed ramps on the rifle did for over three decades?"

I'm not saying M4 ramps aren't a good thing, but they were developed to answer a problem that no one seemed to have until the M4 came along. My understanding, based purely upon the word of a manufacturer as reported in a magazine, is that the M4 ramp is the answer to reliable feeding in a full-auto weapon with possibly weak magazine springs and high cyclic rates.
None of those three apply to any of my AR's, unfortunately.