Rifle extension & M4 receiver

[duc748bip]

First of all its a borrowed picture.
Mine look like the bottom left corner.(The BAD)

Some say it can be done with a Dremel... (Chainsaw sharpening tool I believe)
But me and Dremel always have this love hate relationship.
so I figure if I can just JB weld the gap.
can it be done?
It has a 20" barrel with rifle buffer and extension.

[tujungatoes]

Contact Randall(ar15barrels). I'm sure he can re-cut the ramps for you.

[FeuerFrei]

Shoot it and see how it functions before you do anything to it.
I've seen this on some uppers that work just fine.
Personally I see no need for the M4 cuts on a semi-auto. Always a big debate.

[baih777]

If your not to far from van nuys. You have no excuse to make an appointment with him. Randalls prices are more than fair.

[a308garand]

JB weld will not hold up in filling those areas underneath the barrel extension. On a miss-feed from the magazine, the bullet tip can hit the area you fill, it will chip away and fail- leaving you back at square one.

1-Have the upper receiver feedramps blended into the barrel extension by careful use of a file and polishing/grinding tool. It takes several minutes to get it right, but it can be done.

2-Swap out that upper receiver for one that has not been cut for M4 feedramps. This is actually faster and easier than cutting and blending feedramps into what they were not originally made to do.

[StuckInTheP.R.O.Ca]

JB weld will not hold up in filling those areas underneath the barrel extension. On a miss-feed from the magazine, the bullet tip can hit the area you fill, it will chip away and fail- leaving you back at square one.

1-Have the upper receiver feedramps blended into the barrel extension by careful use of a file and polishing/grinding tool. It takes several minutes to get it right, but it can be done.

2-Swap out that upper receiver for one that has not been cut for M4 feedramps. This is actually faster and easier than cutting and blending feedramps into what they were not originally made to do.

I am having the same issue as the OP. I have an older barrel with standard feed ramps that I want to put on a A3 style upper. Does anyone sell uppers without the M4 detent? It seems like a lot of times they don't specify whether they have the detents or not but it seems most do nowadays.

[Wicked One]

JB weld will not hold up in filling those areas underneath the barrel extension. On a miss-feed from the magazine, the bullet tip can hit the area you fill, it will chip away and fail- leaving you back at square one.

I would Totally have to disagree with this Statement. How much experience do you have using JB Weld? I have quite a bit, and I have use it in MANY high Strength & High heat situations...... WITHOUT Fail!
When "Mixed & Applied Correctly" it's a Very solid, Permanent repair Job. It will bond with & become harder than Steel(again, as long as it's done correctly)...... I have used this same stuff to Repair cracks in 10K dollar Mountain Motors(+700ci Big Block Chevy RACE ENGINES) that make an excess of 800hp & 1200fps. I have also used it on High Dollar Race engine cylinder heads, when you hog them out for every bit of HP(Horse Power) you can get and open the ports up till you see daylight and then use JB Weld to fill it back in and then re-port/Shape them.
Now..... is this the BEST thing to do in the OP's Question....... NO!, But if I had to, I would feel 100% Confident in doing so. (JMHO)

[ar15barrels]

Some say it can be done with a Dremel... (Chainsaw sharpening tool I believe)
But me and Dremel always have this love hate relationship.

I use a foredom tool which is basically just a low speed 1/2hp dremel.
I have done hundreds of them.
There is certainly some feel to it.
It's quite possible to jack up the upper and ruin a receiver and barrel in the process if a dremel gets away from you.

[duc748bip]

At the end I did nothing.. it shoots fine. From the feed position the FMJ sit high enough that it will not cause a problem. But if a round nosedived from a bad follower or weak spring it will mangle up a round.