View Full Version : AR M4 FEED RAMPS!!

10-16-2012, 8:05 AM
I have been in the AR game longer than some of you on here have been walking (1993). Though I have owned a few AR's in my time, I still don't consider myself an expert on this platform. Maybe in part because I've always bought "complete" rifles. Well... for the first time in my life, I am building one, and the M4 feed ramp thing raises question in my mind. HOW IMPORTANT ARE THESE THINGS? I went to look at some of the AR's I currently have on hand. I was shocked to find that my Stag has no feed ramps machined in the upper at all. My LMT has them machined very deep, while my Daniel Defense has barely just a hint of a ramp. All three of these machines operate flawlessly. So.. to make a long story longer... what are some of your experiences with feed ramps? Just FYI, right now due to price and availability, I am looking to purchase and upper with no feed ramps.

10-16-2012, 8:17 AM
A gunsmith near or in cerritos once told me m4 feedramps were just for marketing. Not sure how much one would need them. If you've ran AR's without them and they work, stick with it. I borrowed the following pic from Randall's site for illustration.

10-16-2012, 8:19 AM
From what I have rear/understand, they are most important in carbines since carbines have the fastest and most "rough" cycling. I think even moreover, they are useful when firing full auto. Seems most people say it doesn't matter much.

Hopefully someone can correct me if I am wrong.

10-16-2012, 8:21 AM
All my rifles have M4 feed ramps. You can always dremel the ramps in yourself if you feel the need to. The only combination that is not recommended is a receiver with feed ramps paired with a barrel without feed ramps.

10-16-2012, 8:31 AM
For a semi you don't need them.

HK Dave
10-16-2012, 8:51 AM
I have AR barrels without them and have never had a problem cycling.

10-16-2012, 10:04 AM
I had an upper with the Bad ramps in the pic. Ran perfectly.

10-16-2012, 11:02 AM
I think they only help when you are firing full auto, otherwise they are just a selling point

10-16-2012, 1:36 PM
It's an improvement in the design.
Like the illustration that troysland posted (awesome example, thank you), it will only really cause potential issues when you start mixing and matching barrels with uppers.

There are people that buy a barrel on sale or used, then pop it on a spare upper they had laying around, only to find they had to do some work with a micro-file and a stone to make the ramps mate up nicely. (yes, people like me... it's murphy's law of getting a great deal on a used barrel or stripped upper.)

10-16-2012, 2:45 PM
I don't think any filing is needed. Only the angle of the cut is changed, but not where the bullet touches the ramp. All 4 of the pictured ramps and combos will work just fine.

Obviously, it might not look good. But the cuts in the upper are useless. The bullet never goes lower than the extension so if you have to mix match, it's not the end of the world.

Hop Sing
10-16-2012, 3:26 PM
straight from the Colt factory school, they are not needed unless you are full auto.

10-16-2012, 3:33 PM
They are very important for a high placement on the M4carbine chart.

10-16-2012, 4:20 PM
I think they only help when you are firing full auto, otherwise they are just a selling point

I also asked the same question OP, but when I asked our armors in the military, they told me ^^^^ exactly what's in bold.

10-16-2012, 4:31 PM
They are very important for a high placement on the M4carbine chart.

What does that mean?

10-16-2012, 4:34 PM
It is a near must for proper reliable function of the 6.8 platform.

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10-16-2012, 5:01 PM
The ramps were added to help with reliable feeding in full auto carbines. The only problems I have seen with them is with a rifle extension in a ramped upper, but this problem occurs only sometimes. It is dependent on feed lip geometry and certain loadings. It doesn't occur all the time, but I have seen it. Best bet is to match up the upper type (ramped vs rifle) with the proper extension. This is coming from someone who has been in the AR game longer than many on this site (first AR build was in 1982)

10-16-2012, 5:04 PM
What does that mean?


10-16-2012, 8:11 PM
i think all of this applies to FULL AUTO guns... not Semis like we all have

10-16-2012, 8:32 PM
Can someone explain why these are better for full auto than without? The firing sequence doesn't change in full auto it is just increased.

10-16-2012, 10:29 PM
I read somewhere something about the carbine m4 gas system cycling problems, changing the angle of the ramp meant a slightly better feed rate or some crap ill never need to worry about. Can't remember much but I do remember it was something about how long the tip of the bullet was contacting the ramp before heading into battery.