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Posted: 4/14/2008 3:14:24 PM EDT
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Can someone tell me how or point me to something which tells me how to replace my barrel extension properly? Is this gunsmith work, or bolt on? I have standard feed ramps and need to go to M4. |
If you have any "need" for the M4 ramps other than matching the barrel to a specific upper receiver then there is something else wrong with your rifle. And the correct procedure is to have the larger feed ramps machined into the existing barrel extension. |
Buy a new barrel. There are people that have used dremels to add m4 feed ramps but its easy to botch it and end up trashing the barrel, and the chamber can't be changed from .223 to 5.56 so, your better off buying a new barrel and using your current one to start a new build. I am curious why people 'need' m4 ramps though. |
I think he was being sarcastic... |
Why do you guys NEED M4 feed ramps? Does your upper receiver have the M4 cuts and the barrel doesn"t? That is the only reason I can see that would be a need. If you have a matched receiver and barrel extension then just leave the thing alone and go shooting. |
As stated above, go buy yourself a new barrel of your choice. What makes you think you need M4 feed ramps? IMHO a needless "improvement" for a semi-auto rifle. |
You hit the nail on the head! |
So grab a Dremel and make the receiver extension match up to the receiver. |
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There is no need for m-4 feed ramps in a semi-auto. If your barrel has standard ramps and your upper has m-4 cuts then you can NOT use the two together, so either buy a new standard upper for $100 and sell your m-4 upper for $95 in EE, or buy a new barrel and sell your old one in EE. For all practical purposes there is no such thing as a “barrel extension swap”. |
Yes that is true. I was being sarcastic. And I agree 100% with all those who question the "need" for M4 feed ramps. Let's help stop the spread of this insane obsession with m4 feedramps. To that end, there is a spreading belief that: -if you use P-Mags (by MagPul) they tend to render M4 ramps useless since they present the bullet nose above the area where M4 ramps differ from standard ramps. Thoughts? |
I think that normal mags usually do that too. I -know- that I put several thousand rounds through a rifle with an M4 upper and A2 barrel, the specific combination that is supposed to be "bad", and I never had a misfeed or malfunction. But I built the rifle using all Colt parts, so I guess Colt quality shines through. Or maybe it's because I bought the upper in the late 90s when feed ramps were first starting to show up and we didn't know anything about them. Ignorance is bliss, and all that. |
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I can't help but think..."who freaking cares." If a person wants or thinks they need M4 cuts, then get them. I couldn't care less if your gun has them or not. Personally, I end up with them on every AR because I like Sabre's products and they feature the cuts. Big deal. my $.02 -Jbot |
Neither of us are saying not to get them. Most of the ARs in my safe have them so I'm certainly not -against- them in any way. I just don't see it as a big deal either way. Get the barrel you want, attach it to a "matching" upper and press on. |
I had "bad" a Long Time Ago, and it wouldn't work with ANY mags. But this was long before the Pmags were around. I made it "good" myself and the feed ramps look better than any off the shelf upper you can buy. |
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Just for anyone else reading this, the extension is put on first, then the gas port is drilled. In order to get the new extension timed right to keep your gas port on the top, if you replaced the extension, you would have to be a super lottery winner. It is not really a viable option to replace an extension on a barrel with an existing gas port. I think all of this confusion would not even crop up if online AR parts stores (like Del-Ton) would stop selling extension wrenches and new extensions. Why in the world do they sell them in the first place? Those stores don't sell industrial drill presses or jigs, so why would they sell other specialty tools/parts that you can't really use successfully outside of a barrel-making shop? People see those tools/parts, and say, "oh, I could just replace my extension." Nope! |
Why? - accuracy nuts want them. Who? - People like the "Service Rifle"/CMP/DCM/Camp perry folks who are required to use an AR, but who apply bench-rest rifle building tricks to squeak every last milimeter of accuract out of an AR. Some "DIY" types also want them. |
I am one of those DIY types. Barreling an AR is a lot easier than barreling a bolt action. It is the guys who sell barrels that try to make it a thing of mystery, with Special Proprietary Gages and God Awful Expensive Tooling and, BTW, 20 years experience as a machinist  .
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Fair enough, but you are talking about taking a new barrel blank and a new barrel extension, threading the breech end of the blank for the extension, installing and pinning the extension and drilling the gas port and chambering the barrel. Not Taking an existing barrel and replacing the barrel extension. Correct? |
Yep. Starting from a blank. As cheap as blanks are, I would rather start from a blank than someone else's problem with an unknown history. I could see a real hassle starting from an old barrel the extension was stripped off. Why bother? |
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I appreciate the explaination offered here. Once one realizes that the process is: 1) Chamber, profile and thread barrel. 2) Install/headspace extension. Pin in place as a permanent install. 3) Drill gas port. 4) Drill front sight pin holes. Yea, taking the extension off and trading with one of a slightly different size, just ffor M4 feed ramps seems stupid. Actually, I'm guessing a barrel which needs an extension replacement is scrap steel. . . unless someone has a hnkering for pain! |
We have a winner!!!!! So, now that you have learned the mystery of the barrel extension it is your duty to pass it on to 10 more people… lol  |
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It is a PITA!! I've changed out 2 and it takes some very careful lathe work to get it right. One has to cut the barrel shoulder, then the breech face and finally chamber it deeper. (Not going to happen with chrome lined barrels either) They just don't interchange unless one gets lucky. Only reason I did it was to put the Stag ambi extensions on 2 SS match barrels (for my LH uppers) that I didn't have many rounds through. It is a lot easier to start with a blank. Lyn |
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