So I recently acquired a rare upper in a size that I didn't have. The problem is that the previous owner managed to cause some surprising damage to the threaded area that the barrel nut would go on. While I'm sure that I can remove just enough metal to get a nut on, would I be insane to do so? The crack stops before going into the receiver, and I'm assuming that unless I were to experience one of the few, typical scenarios to cause a catastrophic failure, I would be fine.

I was looking at some possible candidates for build calibers, and while I would STRONGLY prefer putting a Noveske 5.56 barrel in it, I would also rather not destroy the upper because I was foolish.

I circled the approximate area that would have to be removed. (seemingly insignificant)

The previous owner claimed to have caused the damage during a barrel removal.

It'll buff out.

I hope so lol. Are you seeing all three pictures? I’m getting a question mark in a box where the second and third pictures should be.

Thanks for the response

I just see the first picture.

Unless you are skilled at welding aluminum, I wouldn’t use it. Without the indexing slot you risk having the barrel spin and screw up the bolt timing, all bad. Gorilla grip on an upper never ends well. I have seen a few of these in the past. Bubba is alive and well.

Bit late in the thread,but the issue of the crack also should be of concern.
A simple test we use for thin-wall parts suspected of having a crack:
Clean part to bare metal with "extra fine" Scotchbrite
Remove ALL grease and oil,acetone works well enough,wear gloves to avoid skin oil contamination
Mix 50/50 acetone or alcohol with Dykem layout fluid
Touch a q-tip soaked in the mix to the very beginning of the crack,capillary action will draw it into the crack and show how far it extends.

I appreciate the comments everyone. Just to be clear, this was not an upper with a defect. That crack is there only because the previous owner beat the living daylights on the right side of the index notch. Pictures two and three WOULD have shown how it is flared out, hence the crack. Apologies for the second and third pictures not working. I’ll try to get them posted tomorrow.

Stay tuned

Damage looks like it was caused by the pin on barrel removal. I dont see a high spot that will prevent a replacement from going in

If there is a high spot dress any high spots with a flat or half round file or a rod wrapped in sandpaper

If a new barrel that requires an indexing pin is installed the barrel nut will / should spin the barrel and pin to the intact edge. And align to gas port. Righty tighty right?

At least I think so and I did stay at a Hampton Inn once upon a time

Or

go with a blowback caliber barrel

Looking at the picture around the 6:30 position,if that is the flare that seems to be under the blue line,you have a paperweight.The amount of weld/machine time to fix it would be prohibitive (cost>value),and would be a makeshift at best.

No, I've never stayed at a Hampton Inn,but I have been a machinist for forty years.

Is that a Colt 6940? I hope it works out for you

Build it permanent.
Loc-tite the barrel in place let it set up tighten the barrel nut.

Makeshift at best.The problem is the stresses at the root of the threads on a tubular structure.A crack and flare such as this exhibits will have half broken the threads at least down to the limits of the crack.Pushing pressure in such a situation will continue to break the threads at the root,sort of making a aluminum "slinky".

IF YOU MUST HAVE THIS UPPER:
Cut off the threads and thread for at least 1 diameter deep into the non threaded area.
Make a threaded tube (alloy 316L stainless would work well) with a undersized bore(0.030 would be enough).Go for 80% thread.
Fit the threaded tube to the upper dry,making sure the face matches the section bored and threaded.
Lube with permanent locking compound,install tube.I'd also suggest a detente screw from the outside,around 8-32,engaging a dimple in the threads halfway down.
Cut indexing notch,ream and then lap the inside diameter to size.Check for burrs,fit barrel.

Edit:Wondering why I'm bothering when I have a general disdain for this type of rifle? Simple,firearms have bad enough press,don't want to watch the evening news and hear about a rifle failing at an indoor range.

This is actually a Noveske VIS 3... crazy hard to find. Thank you, sir!

This should shed some light on what the situation is. Thank you guys for all of your input. Apologies for taking so long to respond and finally post a better picture. I had a family emergency of sorts out of state.

EDIT... PICTURE STILL ISN'T SHOWING UP...

Got it!! I had to shoot with the SLR instead of the iPhone. As you guys can see in the picture, I would CAREFULLY need to remove the the flared aluminum. The break in the metal isn't deep at all, which is why I have some hope for this upper. I have actually been in the need/wanting a .22 upper for a while, so maybe that's the direction that I should be moving in?

The entire damaged area measures just under .3565 inches deep
The area from the edge of threads to the end of the threaded area measures .45 inches
I just measured to confirm that the break does not actually enter the receiver.

I wonder if it will function properly, since there’s a chance the barrel will not sit properly or have minor movement when if flexes after firing a round. Will bolt even lock back properly if barrel extension is misaligned?

Okay,the numbers were what I needed.I stand by my suggestion to make a repair coupling and install if you must have this upper.


OAL of threads: 0.45
OAL of crack (visible): 0.3565 (nice calipers!)
TPI: 14 (approximate,would need to put a thread gauge on it)

You have no uncompromised threads.

The .22 LR,despite its "pipsqueak" status has the highest breech pressure (proportionally)of any commercial cartridge.Combine that with the hammer effect of a blowback action,it will fail,perhaps not cataclysmicly,but accuracy will degrade in the first few hundred rounds.

I know that this was not what you hoped to hear,sorry.

Would hope that the person you dealt with has a sense of honor,and will refund your money.The cost of repair would exceed the value ,it's a single piece,and all the money would be tied up in the multiple setups to do the repair.

I am not a gunsmith but I am an engineer.

Components are designed and manufactured to achieve results based on known strengths of materials, dimensions, etc. That piece is structurally compromised and there is absolutely no way I would ever attempt to use it as a firearm.