I have seen in the forum that the M4 has different feed ramp cuts. Is this truand if so different from what? and is it more reliable?


please enlighten me!

The M4 feedramp cuts are a little wider and a little deeper and actually extend into the aluminum of the upper receiver. The shorty stocks had a tendancy to drive the bullet tip down rather than into the feedramp and the bullet tip would hit on the flat area of the receiver below the feed ramps and push the bullet back into the empty case. These larger/deeper feedramp were put on the M4 to minimize this.

The cuts are not relevant on a semi-auto but to each his own or her own.

The feed ramps are different on the barrel extensions AND are just as relavant to a semi auto as a full auto.  They were developed because when a mag has weak springs it gets the bullet up slower.  The carbine gas system cycles the action faster.  When these two are combined you can have a bullet get stripped early and get lodged just under the feed ramps.  With the extended feed ramps this malfunction is fixed by guiding the bullet up the reciever ramp and into the extension ramp.  This malfunction does not occur 99.9% of the time and only occurs in carbines.  The ramps also help with certain ammo like blunt nosed HP rounds which very rarely can jam nose first into the upper reciever under the ramps.  Its kind of like a green follower instead of a black follower or an extra power extractor spring.  You dont need it most of the time but it does help reliability.

Ok thats what I was wanting to know

thanks

This might help....
[img]http://photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=10626[/img]

Mike

I had an Armalite carbine that had feeding problems. When I compared the feed ramps on the Armalite to a Bushmaster and a RRA I noticed the Armalite ramps were definitely shorter. I got rid of the Armalite and got a Bushmaster.

Those feed ramps are irelevant on semi auto because that stoppage has only ocurred in full auto mode on the M4,So it was done to make full auto more reliable in the M4 because it operates a bit faster.Ive had my pre ban bushie carbine 11 years an 17000 rounds later ive never encountered that problem,so in my experience its irelevant on semi auto weapons if it was relevant on semi autos colt would have used it on their semi auto carbines 25 years ago and I seriously question weather the stoppage realy relates to full auto or just bad quality control at colt.Canada makes a carbine version that has never had this problem and bushie select fire models as far as I know have never had this problem .only the colt it seems.I just think that they did it to protect their weapon from patent infringement because they are the sole suppliers to the US military and want to keep it that way. Maybe thats why the government cannot sub contract out the M4 because of colts patent on M4s supplied to the military thats probably why other companies do the feed ramps on weapons to civilians and law enforcement because it only applies to military supplied M4s.I doubt if other companies do this to their rifles supplied to foreign governments if so some one point me in the right information path because id like to know if other companies supplying foreign militarys do this feature.

Simple,

I build then fire the XM177 and go from there

thanks for the pic that explained everything

--Rob

Untrue these days.  It used to be that only Colt had this feature but they are now showing up on civilian semi-auto rifles from multiple companies.  Do a search (can't get it to work for me right now) but there was a thread with pictures of semi-auto Armalites and others with the M4 ramp cut.  I also recall LMT for sure, and possibly RRA and Bushmaster now having these.  Model927, you never needed them in 17000 rds, but that doesn't mean others do not - not everyone has the same setup, mag springs, cleanliness, climate, ammo, etc. that you do.  Some have had problems with soft point rounds without the cuts as well.  How many soft point rounds have you fired out of those 17000?

This is false.  The rifle has no idea if its operating semi auto or full auto.  The firing cycle is the same and that has no bearing on the malfunction in question.  Full auto does not speed up the movement of the bolt carrier.  The rounds are stripped just the same either way and will jam the same either way.

All i can say is that initially i was sceptical about the m4 cuts, now i am a believer.

My buddy had a new bushmaster that would consistenly get FTFs.  After looking at the usual suspects i noticed tiny copper scrapes at the bottom of the upper mag area, just below the cuts on the extension.  I made the cuts and dumped a 100 rounds through it as fast as i could without a hiccup.  I plan to make the same cuts on my BM range rifle which has occasional problems and on my RR upper which will go on one of my social rifles.

Its a free fix that has no downside.  You are not cutting ramps for the bullet nose to slide on, you're cutting clearances for the nose to have room to rise up and hit the extension ramps.

Hollow points and soft points have accounted for roughly 3000 rounds of the 17000.To devl what I should have said is the carbine operates under higher pressures and stress ,you are right not faster.I do keep my rifle clean but Im not anal about it,I shoot 500 rounds at a time and thats split between 3 ARs all bushmaster but the 500 goes through 1 rifle at a time not 500 split between 3,I lube shoot and then clean.For mag springs I use the standard GI ones.The only thing special I use is a les baer hard chromed extractor and heavy duty spring.I use a heavy buffer also.As far as climate I live on the east coast so although it gets hot in the summer 90 t0 95 my rifles see more wet and wet cold weather I also have HBARS on all 3 and they are all carbines 14.5 with phantom 11.5 with 5.5 supressor and a 16" the 3000 odd rounds were 2000 hollow points 1000 soft points and all out of the 14.5 barrel.I have had magazine related stopages but never nose dives while feeding,Maybe when I build my first and next AR,all the other 3 are factory rifles except the 14.5 wich started life as a fullsize rifle,Ill get the ramp cuts just to see for my self,I guess I could just do the barrel extension my self.My question is do you follow the angle of the original ramp angle or go more straight to make sure the rounds hit it straighter?

Here's a pic of the extended feedramps on my CMM/DPMS M4 upper.  It looks just like the Colt extended feedramps and they both appear to follow the original ramp angle and are not straight.


[img]http://a3.cpimg.com/image/BF/06/19895743-00e6-02000180-.jpg[/img]

[img]http://a2.cpimg.com/image/AA/BB/20163242-27d3-02000180-.jpg[/img]

I've seen someone mention that they should be straight but I would stick with Colt's version and follow the orginal angle.

Thanks YOJIMBO I ordered a new carbine upper today,M4 profile with the phantom.Im gonna do the cuts on that,I figured if I do it it might as well be on an assembly as close to the M4 as I can get and its also my first flat top.I didnt get the removable handle because Im gonna put a pop up rear sight on it and while Im on the subject does any one know what kind of pop up rear sight I should look into? and how much?I want one that socom uses if possible,Im not up to date on some of the add ons because ive always had the A2 fixed handle.Maybe now with the new upper Ill have to get a RAS system for it.

Depending on who you ordered it from, it may already have the feedramp cuts...

It was I that mentioned in the past that the factory has the angle wrong.  Don't think these engineers ALWAYS have their act together.  There have been design boo-boo's in the past.  I think this is a design boo-boo.  Simple logic folks.  Not rocket science here.  Open your ejection cover, and peek inside for yourself.  The bullet travels along a path indicated in BLUE.  The boo-boo factory ramps follow a path indicated in RED.  I create my feed ramps to follow the BLUE path.  My ramps work great.  I can purposely hold the mag unlatched (which allows the mag to hang low about 1/8"), relaese the bolt catch, and the cartridge SWOOSHES into the chamber with a beutiful swoosh sound.  If I lower the mag more, the bolt is unable to grab the cartridge to feed it, and causes a bolt-over.

[img]http://pic2.picturetrail.com/VOL33/1216349/2303971/27862763.jpg[/img]

The cartridge enters the chamber from the angle dictated on the barrel extension feed ramp, which is the red line.  

One could have extended feed ramp cut at 11 and 1 o'clock and still be able to chamber a round with no problem.

Did you even try looking into your upper as the bolt pushes the cartridge forward ?

The round is held in postion by the magazine lip.  The bolt pushes the round forward as the round slides along the mag lip.  The round does not change from any direction until the bullet tip contacts the ramp.  That is the point - hopefully the bullet contacts the ramps, and NOT the blunt barrel extension.

Now, at what angle will the bullet tip be pointing if the bullet is hanging too low.  The bullet will still be pointing in the direction that the magazine is directing the round.  This angle is straight forward - as in the bolt is pushing the round straight forward.

But hell, I could be wrong.  Please give me your explanation how the bullet tip would ever be in a position to strike those boo-boo ramps.  The cartridge is facing straight forward as it approaches the ramp.

Whatever works is okay in my book.

Feed ramps do, of course, become [i]very[/i] important when you move to different calibers.  If you try shoving a 240 gr soft point in the chamber (.300 Whisper), you quickly realize that you need new (widened & deepened) feed ramps.