Almost daily, I get someone asking if RRA uppers have “M4 feed ramps”.  I honestly have to answer no. I then get a reply saying, so and so bought one from Brand X, and it had “M4 Feed Ramps”. Or, can you put “M4 Feed Ramps” in it?
NO, the upper your friend bought from Brand X, does not have “M4 Feed ramps”, and NO I cant add them, that would require heavily modifying the barrel extension.
Barrels are built with 2 types of barrel extensions. There are rifle barrel extensions, and there are M4/Carbine barrel extensions. Almost all of the complete commercial uppers sold have rifle barrel extensions. Colt, and LMT are the only I can thing of that use M4/Carbine extensions.
Here is a pic of the 2 extensions next to each other.

You can see the rifle extension, does not have nearly the pronounced feed ramps.

Here’s another pic from the bottom where it is much more obvious.




Here is an M4/Carbine barrel extension installed on a LMT upper receiver.


You can see upper was designed to accept this barrel extension, and there are “feed ramps” leading to the barrel extension.

Here is the common misconception:


This is a picture of a RRA upper receiver with a rifle barrel extension installed, that has been modified. The only thing accomplished in this picture was some of the protective hard coat anodizing was removed. This unfortunately, is what many people consider to be “M4 feed ramps”.  They are not.

This is a properly installed rifle barrel extension in a WOA Upper that was built by John Holliger.  


You can see the feed ramps in the barrel extension, come down to the receiver and end. There is absolutely no reason to modify anything. A lifetime of use can be had from this upper without a single FTF.



This is a rifle barrel extension installed in a upper with feed ramps. The less steep angle of the rifle extension, extends out past/over the feed ramps. If a cartridge fed into the feedramp, it would definitely get stuck on the extended portion of the rifle extension.

The next time someone tells you about their “M4 Feed Ramps”, or a dealer sells you an upper with “M4 Feed Ramps”, ask what barrel extension was used.  I have a feeling 99% of the people out there who think they have “M4 Feed Ramps” have standard rifle extensions, with dremmeled receivers. Buy what you want, but know what you are getting.

Ive never liked the idea of grinding past the annodizing on the reciever just to add something thats not really necessary to have a reliable gun.

Thanks for the info.

Quoted: I get red X's.

Sorry, my whole site just went down. Hopefully my ISP will fix it soon....

Agree that if you dont have a barrel with the M4 extention, getting an upper with them isnt a great idea. But getting the barrel and receiver with the extended ramps I think isnt a bad option. Surely not necessary, but if building something from the ground up I thik its good to have the option and I would rather have them then not in that case.

Some Dept down here, I dont recall which, uses some type of soft point ammo that did not feed well in their non-M4 feed ramped guns. I swear it was the Dept. of Env. Protection or something. One of their guys shoots wth us and he was having problems. Shooting the same ammo in a Colt with the feed ramps was 100%.

Quoted: Neil, same happened down here with local LEO's and Bushy carbines w/ no ramps. Only difference was the use of 75 grain Hornady ammo. During fullauto fire feeding was nowhere near 100%. Maybe more like 95%. These uppers have since been replaced by LMT CQBR uppers, and they feed/fire/eject all ammo 100%. It might not matter to most, but if MY *ss is on the line I'd rather have take what works all the time under all conditions. -Cap'n

A local had that same problem with Bushmasters and TAP ammo. It turned out the new magazines were causing the followers to drag, and slow down the full auto feeding. Never had a issue semi auto.  They ran the mags until they were "broken in" and after that all was fine. Finding what works all the time, is unfortunately a trial and error type of thing...

Quoted: actually, no, it does not. dremel makes chainsaw sharpening bits that have the exact conture of the M4 ramp. Sure, it will not be a "Colt M4" feed ramp but it will be identicle in every form other than the small amount of anodizing that will be removed. they are sold in a series so a person can grind out the material and then polish it. it's pretty easy. i'm not saying it's right or wrong, just that cutting the ramps is a simple task. installing a new barrel extension on the other hand, that's a major pain in the ass!

OK, so you remove the material, that goes no where; you still dont have any feed ramps. Im order to have "feed ramps" they need to ramp up to something. If you dont have an M4 barrel extension, you have nothing to "ramp" to. The ramps cut into the barrel extension, are a completely different angle on the M4.

Quoted: I posted this question a while ago and got no response, I have a Bushmaster barrel installed in a reciever with M4 cuts, it works fine so far, about 200 rounds, but could I or should I dremmel the cuts into the barrel extension to match the reciever?

If its not broke, dont fix it

I have owned and shot dozens of Colt M16's over many, many years.  95% of them, of all barrel lengths did not have M4 feed ramps and all worked 100% provided they were feed good ammo out of good mags.

I currently have 2 Colt M4's, real ones, and they work fine too.  Is the M4 cut really necessary?  My experience says that they are not.  Good mags, in good repair, with lips that feed the rounds at the proper angle are.

The M16 system was never ever intended to shoot other than FMJ ammo.  That said if you shoot match type ammo with its small hollow point you will experience zero malfuntions due to lack of M4 cuts.  Lead exposed tip ammo is not a good idea in any military type weapon, M16s, FALs, G3s etc.

If I feel the need to use hunting/anti-personell ammo I use ballistic tips.  They feed 100% due to the plastic tip that does not deform under beating around in the mag or during feeding.

Removing the anodizing on the receiver is not a good idea.  The upper is aluminum and soft,  once you go thru the hard anodizing you expose the aluminum and suject the feed ramp to excessive wear by the ponts of the full metal jacket projos we use most of the time.

Denny

Tell me...

Is there anything wrong with using a standard barrel extension along-side a receiver with M4 feed ramps?

Quoted: Tell me... Is there anything wrong with using a standard barrel extension along-side a receiver with M4 feed ramps?

Yes, the ramps in the upper would lead up to a flat wall before the ramps in the extension began. Not usually a good thing.

Quoted: Quoted: Tell me... Is there anything wrong with using a standard barrel extension along-side a receiver with M4 feed ramps? Yes, the ramps in the upper would lead up to a flat wall before the ramps in the extension began. Not usually a good thing.

That's what I was afraid of.

Any chance you can post a pic of this?

All my LMT uppers are assembled, or I would have posted a pic. I'll do so as soon as I get more in.

Bigbore, when you state that RRA uppers don't have M4 feed ramps, do you also mean they don't have the "dremmel ramps"? I recently purchased an RRA Entry Tactical that came with "dremmel ramps" as you helpfully explained in an earlier thread I started: I didn't cut these "dremmel ramps". They came from the factory that way.

RRA has the (now coined)"dremmel ramps". Without an M4 barrel extension, you cant have M4 feed ramps.  The "Dremmel Cuts" did not come from the factory (The factory would be the foundry), the "dremmel cuts" were dont at RRA when the rifle was assembled.  I didnt start this thread to argue the points of whats right and wrong. I just want people to know what they have.  

If a properly set-up and maintained rifle with quality magazines in good repair with in-spec lips will never FTF due to the bullet tip missing the standard barrel ramp and impacting the standard receiver, then there is no worry that a bullet tip will ever pick up the "M4" receiver ramps and get caught on the ledge formed by the standard rifle barrel ramps. On the other hand, if a bullet does contact the receiver ramp first and get hung up on the ledge, then it would have missed the barrel ramp on a standard receiver as well and likely (?) misfed - a misfeed that presumably would have been prevented by the extended ramps.

You answered your own question. "a properly set-up and maintained rifle with quality magazines in good repair " will be just fine. IF you pick up a bad mag that constantly hits the "dremmeled" area you will eventually have problems. If thats the case buy a new magazine. Watch a round feed from a good magazine, its no where near the "dremmel cuts".   The area "dremmeled" is insignificant. Ball ammo hitting the same spot on a non-dremmeled receiver will work fine.
Why do places even add the "dremmel cut" -  I'll go out on a limb and say marketing.

Quoted: So do factory LMT uppers have true M4 feed ramps or just the "Dremel ramps"?

LMT upper receivers were designed with the ramps to work with a M4 barrel extension.

First of all let's all say thanks to ADCO for taking the time to reply numerous times in this thread and for the great pictures they took to explain all this.  It is time consuming work and it was all done for free as a service to the members and guests on this board.

I am not a hobby gunsmith and neither is ADCO.  The info we post is from working on hundreds of guns and years of experience with them.  We take time to reply to these threads as a service to you guys.  We are not here to argue, flame, just explain our experience.

I would like to summarize some of this thread.

Receivers are anodized to reduce wear.  Removing anodizing on wear sufaces is not good.

M4 barrel extentions have their own unique angle.  Adding them to a non-M4 upper is not good.

Rifle barrel extensions are used by every barrel manufacturer with the exception of Colt  and LMT.
They should not be used in uppers with TRUE M4 cuts and FTF can occur.  The reverse is also true.

If you want or need a true M4 feeding system you have some options.

Buy a Colt M4 Upper and barrel.

Buy a LMT barrel and upper.

Have us or one of the other gunsmithing companies build you one.  It is not cheap but  many of us can do it.  This involves getting a SS or chrome moly match barrel blank or at least an unchambered , unfinished barrel and having us fit an LMT M4 barrel extension to it and then cutting the chamber and fitting it all up.  LMT will sell gunsmiths M4 barrel extensions.  If you go this route you can get the exact barrel you want.  Rate of twist, brand, length etc.

I know some of you have had success with your dremel tool and have made guns that would not feed correctly improve.  That is great and I am glad ya got the gun working.  We have not heard from the guys who tried it and wound up with a hacked up barrel extension and upper as folks have a tendency not to post their failures.

This is a good thread with good info and some great pics courtesy of ADCO and it should be saved.

As to ADCO's comment on "marketing" it is right on the money.  You want real M4 do one of the things I suggested above.  Don't get conned into buying and "M4" that really isn't.  The real deal is only available as stated above.