Can someone repost the pics of the M4 feedramps. I have tried doing a search and can't find them.

Pic server is down but the SEARCH function here is amazing..

This is a close as I can find tho they're not correct, someone obviously (check the lack of anodizing) added the extended feed ramps later.



More threads with X's.

http://www.ar15.com/forums/topic.html?b=3&f=12&t=161616

http://www.ar15.com/forums/topic.html?b=3&f=118&t=171671

http://www.ar15.com/forums/topic.html?b=3&f=12&t=157413

http://ar15.com/forums/topic.html?b=3&f=12&t=159623


[bored kode]

Thanks. I was using the search function and I kept getting the "no items found" message or whatever it states.

it's on the photoserver, browse through the thumbnails and you will see it

i'm pretty sure colt's M4s come with the feedramps extended down into the reciever, bushmasters do not however

Quoted: "no items found"

try "feed ramps"

Exactly. Everyone has the larger cuts on the breech face, the M4 cuts extend into the reciever.

Tweak,

That pic is one I posted of my CMMG/DPMS upper.  AFAIK, the extended feedramps were done by DPMS specially for CMMG's 16", 1/7 4150 barrels and it IMHO, they doen really well.

My upper has worked flawlessly so far but how much of an issue is the lack of anodizing?  Should I worry about possible damage to the areas with no finish?

picture from [b]Troy[/b]

[img]photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=2881[/img]

Well there would be a picture, if the photo server ever works again!!

Actually, the feedramps are incorrect, as they are on my CMMG/DPMS upper.  They are better than no feedramps as they do line up with bullet tips lower in the magazine than standard feedramps, but not as early as correct feedramps.  Seeing as how it's extremely rare malfunction anyway, they're not really needed, just nice to have.

As for problems?  I seriously doubt it.  The 4150 steel is hard, and it's extremely rare that the bullet tips will ever make contact with the upper receiver part of the feed ramps.  The aluminum of the upper receiver isn't exactly soft either, probably a lot harder than the copper jacket of a bullet.

my rra car a4 has the same feed ramps as the m4 shown in the picture

[img]http://www.hunt101.com/img/054141.jpg[/img]

Stolen from Troy a long time ago.

Quoted: My upper has worked flawlessly so far but how much of an issue is the lack of anodizing?

Just that the ramps were obviously added after the part was anodized so they were probably done by hand.

Should I worry about possible damage to the areas with no finish?

Nah, the rounds really don't slide up the ramps, they sort of bounce their way up. I've added a lot of extended ramps to carbine barrels (short blunt projo issues) and never seen any damage. Not that it couldn't happen, just that the chances are really remote.

Quoted: The 4150 steel is hard,

To clarify, the barrel extension is made of SAE 8620 steel (yes, like the bolt carrier for those of you following the thread in the BFI forum.) while the barrel is, or should be, 4150 steel. I believe the other two spec'd steels that can be used are AMS 6276 and 6274.

The barrel extensions are carburized (surface hardened) to a depth of 0.01-0.015 THEN ground to size. That means you're probably looking at less than 0.01" of hard metal. Removing more than that will put you into the softer steel beneath.

I don't know how deep the T6 temper is in the 6061 Al and the hard anodizing does add some wear resistance so theoretically grinding the ramps after the parts is made can accelerate wear.

My carbine also has the same feedramps shown in Yojimbo's picture.  That doesn't make them 100% correct.

I stand corrected!  Damn Tweak, your knowledge of AR15/M4/M16's down to the very last detail is astounding.  Thanks for correcting me and contributing to our ever growing knowledge base. [beer]




THEORETICALLY this might be an issue if the bullet tips ever actually made contact with the aluminum part of the receiver.  This is extremely rare as it would require a magazine with a VERY weak spring to be used in a rifle with an extremely fast action.  Usually the 11.5" barrels and under.  This situation is extactly what the extended feedramps were designed for, and this condition is SO RARE it's hardly worth talking about.  How many tens (hundreds?) of thousands of AR15/M4/M16 series rifles are out there, functioning just fine without feedramps?

Quoted: How many tens (hundreds?) of thousands of AR15/M4/M16 series rifles are out there, functioning just fine without feedramps?

According to coldblue, the ramps were designed after extreme cold weather testing of the M4 showed feed problems. That would explain why the problem is rare. The feed problems were related to the temperature.

The feed problems I have encounterd relate to short blunt bullets and a combination of incorrect parts. I correct the incorrect but it's more difficult to make agencies change their loads. The issue becomes dangerous when those same short, blunt bullets are not firmly crimped into the case. In that case, misfeeds can cause stubbed bullets which can spill unburnt powder into the action or even kB's.


[speeling]

Bushmaster carved ramps into my M4 type. I sent the upper to them for some warranty work and the went ahead and did it free of charge (as part of the warranty work).

So what should I do if all my bullets are being severely scratched as they are pushed up the feed ramp? It happens with all my mags and is clearly due to the fact that the chamber/feed ramp is slightly recessed from the rest of the upper receiver and the bullet strikes the bottom before bouncing up to the feed ramp to be chambered. I'll try to take a pic, but basically I can see wear on the area just under each feed ramp (no M4 extension) and the bullet jacket gets gouged every time (accuracy sucks). I'd ditch this rifle, but I don't want to leave someone else with the problem.

T6 temper goes all the way through.  The heat treatment is achieved by aging a part at a specified temperature for several hours.  It is essentially impossible to do this on selected areas or layers.  

I have a 14.5" Bushmaster without M4 feed ramps and have experienced stubbing with some regularlity (on the left ramp only).  Neither new LaBelle mags nor old GIs with new springs solved the problem.  Bullet tips on the left side ramp sometimes impact the receiver (which is slightly proud of the barrel extension) and have peened over the aluminum,  leaving slivers of bullet  jacket  shaved off and lodged between the barrel extension and receiver.  On a few occasions, cartridges have gone no farther then the barrel extension lugs, leaving them gouged and bent from an amidship hit.  Things must roll around in there pretty good because, as a test, 1) I've put downward pressure on a loaded magazine, 2) cycled the bolt slowly by hand, 3) carefully observed travel of the cartridge and 4) never been able to cause a bullet tip to impact below the barrel extension feed ramp.

So far my attempt to remedy has been limited to polishing the ramps while maintaining the same angle.  This has removed only a small crescent of material from the aluminum receiver, but has caused the interface between the receiver and barrel extension to become quite sharp.  Apparently this small step has not been sufficient as  jacket material continues to be deposited on the peened surface of the receiver.  Perhaps I need to be a bit more aggressive.

Any thoughts on the matter would be appreciated.

Thanks bigbore, I'll keep reading.

so,,you shoot enough rounds through a weapon that without m 4 feed ramps would be troublesome,and the ground ramps into the alminum reciever starts to wear before  the steel,,,


just a rant..hell know yor weapon,ammo,mags etc. intimately! observe, document, track, monitor etc.