Barrel extension replacement

Memnoch

Memnoch

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Hi, here is a question for the AR Gurus out there. I own a Armalite M15A2 with carry handle. My rifle is fitted with "rifle" type feed ramps (not the "M4" type feed ramps). I would like to change my upper receiver for a flat top receiver (only the receiver, not the whole upper assembly). The thing is that the new receiver has the "M4" ramps cut in it, and to properly do this, i would have to change my barrel extension as well.

I have looked at Brownells' videos, they are very well made but i did not find anything on how to replace the barrel extension? Is it complicated? Do special tool are involved? Anybody have a good reference material to do this? What is involved in "indexing" the extension?

Thank you very much.

Memnoch
 
Dude I think you are over complicating things.

The simplest solution is to buy a M16A3 style non feedramped upper Reciever. They are out there, hell Larue even makes a Stealth upper with no feedramps which looks #####in.

But if you insist, there are much more complicated ways of doing this.

barrel extentions are pinned to the barrel. Can it be removed? Sure it can!

But Removing the pin will be tricky. One possible solution is to drill a tiny hole through the pin, fill it with oil and insert a smaller pin in there and hit it with a hammer to hydraulically push the pin out. This Im assuming you have some sort of access to a machine shop.

There are several other ways of doing this but honestly unless you really want to do this the juice is simply not worth the squeeze.
 
For all intents and purpose, you cannot change your barrel extension. Why? The barrel extension is torqued on until headspace is correct, then the barrel extension pin is drilled and inserted, THEN the gas port hole is drilled to index with the barrel extension pin. If you replace your barrel extension, there is no way of knowing if your new barrel extension will line up with your already drilled gas port, when it is torqued for headspace.

Hope that makes sense.

If you have a lathe and some skills, you may be able to adjust the treads on your barrel or extension to make this work, but the question would be, why, that's a lot of work for no advantage. I'd forget the extended ramps, if you really really want to make work what you own you could take a grinder to your existing barrel extension.

Really what I would do is but a new upper receiver.
 
Barrel extensions are threaded to the barrel. The indexing pin is just that - an indexing pin.
As pointed out, it is far easier to use a matching upper, than try to change the extension.
The extension is threaded to the barrel and torqued. To remove or install one, you will need the appropriate tools - it is not unlike installing a barrel on a receiver.
I have made an AR barrel from a blank, not much different than fitting a barrel to anything else. The gas port was the last operation.
 
Long before the "M4" feedramps were named that, lowering feedramps was something that was done to make the AR15 feed better and be more reliable.

The solution to the M4 upper and standard feed ramp is for a COMPETANT gunsmith to lower the feedramps to match the M4 upper.

I have seen ones done by Bubbas. The penalty for doing it wrong is to buy a new barrel.

Casey
 
One issue with machining the ramps after the fact is you have removed the HCA - so you have soft aluminum on the ramp, it will gradually wear deeper, and much faster with longer bullets.

It can be done yes, but it really should not.
 
KevinB said:
One issue with machining the ramps after the fact is you have removed the HCA - so you have soft aluminum on the ramp, it will gradually wear deeper, and much faster with longer bullets.

It can be done yes, but it really should not.
Click to expand...

Quite true but...........

With regards to the original question, it is the feed ramps in the barrel extension that need to be lowered to mach the new upper with M4 ramps that he has. There is no HCA or aluminum in the barrel extension;)

Casey
 
I know it sounds kinda dumb - why don't you just buy the upper receiver without the M4 feedramp? CMT aka Stag does produce flattop without feedramp cut.
 
Because i had issues with the no "M4" feedramps. At many occassions, the following occured to me: I have a stoppage, the bolt is partially foward, after investigating i see that the bullet didn't climb on the ramp and is caught on the receiver below the "Rifle" ramp. Bullet get pushed back inside the casing.

Now i know, people told me many times that it was because of poor mag quality. But the same mags worked fine in other people's AR. It feels like the mag, for some reasons is sitting just a few thousands of inchs too low so that once in a 100, a bullet end up not aligned properly.

I have read others here with the same problem. I think this is a tendency that the older Armalites used to have.

I have no warranty on the gun and cannot send it back.

Thats why my friend.


Mem
 
What is the ammuntion that have problems? if you are using 52gr or 45gr JHP, it is not uncommon to have this issue with standard feedramp.
 
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