I just saw the second "over-ramped" M4 barrel extension on an SR-15 Carbine to be returned here (KMC)for repair in the last 30 days.
But that is just half the tragety (i.e., original parts can't be repaired).  The other half is that the current owner's of these two carbines are not the original ownwers.
They purchased these already "broke" guns from subsequent owners, two of which had dremeled/cut/polished the feed ramps way down into the aluminum receiver, and way too wide in the barrel extension as well.  So what happens is the rounds initially feed out of the magazine OK, but then are not ramped up into the chamber void.  Instead, they enter the barrel extension so low in position, that the bullet tips strike & stop on the rear edge of the chamber.
Buyer beware!
Check out (hey, print out a copy and put in in your wallet) of a properly ramped barrel extension here on ar14.com, and carry it with you to gun Shows and Pawn Shops.  
Don't buy someone elses wall hanger.
And parents, do you know where your dremel tool is right now?

Thanks for the heads up cold blue.

The extended feedramps on my carbine are cut wrong as well, but I have no feeding troubles.  Yojimbo had a picture of what they look like in comparison to correct extended feedramps.  Basically it looks like they extended along the outside edge of the feedramps instead of the inside.

When you push a round down into the magazine somewhat to simulate a round that hasn't popped up enough, you can see that the ramps and bullet tip don't line up.  However, if the bullet sits just a little higher than that in the magazine they will load through the extended feedramps properly.  So I am getting atleast some feeding benefit in addition to the bullet tips not denting/deforming.  Also, my carbine had a MUCH faster action before I added a heavier buffer & bolt carrier and I still didn't have any problems with FTFs that had anything to do with the upper.

I've often heard that the best way to get an unreliable 1911 is to take it home and use a Dremel to "polish the feed ramp".  Makes sense that it apply to ARs as well.

Funny, my AR carbines have fed reliably for years without feed ramps....

I did this mod, sucessfully, on my two M4gery's. If you are going to do this, be aware that only a VERY LITTLE bit of the aluminum is actually removed from the upper receiver!!

It's my understanding, and I'm sure someone will correct me if I'm wrong, that the feedramps were for the longer M895/M896 ammo under full auto conditions.  Since I either shoot Q3131A or M193 in semi I don't see this as a need.  My Bushmaster XM177E2 doesn't have them and I've never had a feed problem.

Ive fed BH 68gr through mine without problems.  I'll soon be testing some 75 and 77 grain loads.  I doubt I'll have problem.

I agree, I doubt you'll have any issues.

Some folk just can't understand that a reliable maker is not going to have a product out there that needs improvment with any dremel tool. OH YUK, to those poor weapons, a total derrr head that did that!
Jack

One of my favorite fraises is:

A LITTLE KNOWLEDGE IS MORE DANGEROUS THEN NO KNOWLEDGE AT ALL!

To demonize the Dremel (one of my favorite tools BTW), is like demonizing a gun in the wrong hands.

Not sure where you heard that.Polishing the feed ramp is something most 1911 smiths do in a reliability job.

My KAC shoots pretty good the way it is with no modifications.

Because if you dont know what you're doing, and you over polish and change angles, not only can you effect the feed angle, you can can remove metal that supports the cartridge case.

Colt's original advertizing for the carbine stated that it had improved feed ramp geometry to facillitate the feeding of "commerical ammunition." That would be SPs and HPs. Rounds with blunt tips and short OALs will have trouble feeding, eventually, without the M4 ramps. FMJ ammo is usually not a problem.

"Some folk just can't understand that a reliable maker is not going to have a product out there that needs improvment with any dremel tool. OH YUK, to those poor weapons, a total derrr head that did that!"

I've actually successfully cut ramps in my 14.5 but I still preffer "forged or anodized in" ramps.

The correct way to do this is to buy the right Dremel heads (one cylindrical stone and one cylindrical polishing bit), then at the same angle, deepen the ramps slightly till you just barely get into the upper, polish these, then remove the barrel and deepen the ramps on the barrel extension by a couple thousandths and polish and blue them.

(it is important to do this to make sure the upper won't soon wear enough to allow the bullet points to hang up on the "now overhanging ridge of the barrel extention".)

[b]AS far as I know the ramps were only added with one thing in mind (getting the M4 to pass cold weather reliability tests).[/b]

If you don't know the difference between a competent smith using the proper tools and some WECSOG graduate with a Dremel like me, then I've got a bridge to sell you.

???  Cold weather tests?  You must be thinking of the twist rate being changed from 1/14 to 1/12 back in the '60s.  The feed ramps are for reliable feeding of SP, HP or other non-FMJ ammo in full auto.

"??? Cold weather tests? You must be thinking of the twist rate being changed from 1/14 to 1/12 back in the '60s. The feed ramps are for reliable feeding of SP, HP or other non-FMJ ammo in full auto."

The Army doesn't give two shits about soft point ammo. They aren't allowed to use it. There were cold weather tests and the M4 before feed ramps did fail them. The only groups that use SP or HP ammo are groups like Delta force that are small enough to order their own special components if need be- the Army wouldn't change 3,000,000 guns to make a couple hundred guns that will be used with HP or SP ammo function better.

[b]Try to remember also that the M4 is not evn full auto, only the minority of M4's (the M4A1's are selective to full auto)[/b]

Gunsmiths do use dremel tools. A competent gunsmith using a dremel is a lot like me using a dremel. (I have worn out several tools, lots of time with them). The proper equipment as far as I know does not cut the ramps at all, instead it FORGES THEM IN.


Professional Gunsmiths still use rotary tools to polish 1911 feed ramps also. This is the only way I know of to polish a feed ramp, outside of factories like Kimber.

[b]Cutting ramps properly is a pain in the ass (because it requires barrel removal and about 45 minutes of my time- including time spent cleaning metal out of the chamber), I don't reccomend it, I instead reccomend buying a LMT upper from MSTN for $175. [/b]

Since when? The rule of land warfare only applies to "international war". War between signatory states. Besides the Abu Dhabi carbine wasn't designed for sale to NATO.

My own cynical view is that Colt developed the ramped upper simply so they could have a patented gizmo that would assure them that FN couldn't underbid them on the M4 contract; since FN had already taken the M16A2 business away from them.

Now two of my ARs have shelves on the uppers that extend very slightly past the rear edge of the barrel extension.  On those two I've taken a semi round needle file and ramped the overhang to blend into the feed ramp. The file won't cut the hardened steel of the barrel extension, so I could cut the "ramps" without having to pull the barrel, and I didn't have to worry about overcutting.  After the ramps were filed in, I polished the whole combined ramp w/600 grit paper wrapped around the needle file.

Smooth appearance, and perfect feeding. What more could a guy ask for?[:D]

The feed ramp angle change was the direct result of the M4 failing extreme cold reliability testing at Aberdeen Proving Ground when the Marine Corps was preparing to adopt the Carbine as a replacement for the .45 Cal. M3 "Grease Gun" in the mid 80's.
Colt came up with the deeper feed ramps and second time around they passed.
We then noticed the cyclic rate at ambient temperture increased slightly.  So we thought this was a good change, as it apparently "smoothed" feeding.

Coldblue...THAT'S customer service.  
PSA's, thanks.

S2

Quoted:
[/quote]If you don't know the difference between a competent smith using the proper tools and some WECSOG graduate with a Dremel like me, then I've got a bridge to sell you.
[/quote]

I've dremeled both my 1911 feedramps and never had a problem.I guess no matter what firearm one is working on, if you're incompetent and  don't know what you're doing, leave it to a professional.

Exactly.  Some of my Colts came with them from the factory.  But for my ones that didn't,
"If it ain't broke, don't fix it."

Although I don't shoot a lot of it anymore, there definitely [b]is[/b] an issue with softpoint ammo with my standard feedramps. I solved the problem years ago by switching to Nosler Ballistic tips in my reloads. Just for the heck of it I chambered/unloaded/re-chambered a few softpoint rounds in my Colt M4 carbine with the extended ramps and the bullets weren't deformed at all.

That's a bit of nit picking isn't it? The M4s are burst guns, that counts as full auto under the legal definition. The M4A1s are "semi to full auto". Both versions are "selective."



No way bud. The upper forging is SOLID, it's a little difficult to "forge" the extended feed ramps into the interior of a solid part. The feed ramps are cut along with all the other features on the upper.




I have never had to remove a barrel to do this and I've got hundreds under my belt. Plug the chamber and interior of the barrel extension on the next one and save some time.