AR lower flaw fix?

[thatsteveguy]

I recently purchased online a billet lower. I had 3 lowers come in and to be honest I just gave a cursory look at them. When I first saw this "flaw" I thought it was just the transition line. <D'oh!> After I took possesion from the local FFL I started to build it and noticed this was a flaw behind the rear take down pin hole not a transition line. <D'oh! again> It's not a crack but feels about .010 above the flat surface. I'm thinking the finish cutter didn't "finish" the blend from the angle area to the flat area. I've contacted the seller and am awaiting instructions from them for a return. My question to you machinists and gunsmiths; is this an easy fix and then re-anodize or is that something that is not easily fixed? I really don't want to re-dros another lower obviously.

This is what the other side looks like. (normal)

[ar15barrels]

Cutting through the anodizing is no fun.
The best way to fix it will be to strip the anodizing, re-machine and re-anodize.
It will be cheaper for the manufacturer to just give you another one.
You will have to re-dros that one as you are starting a new DROS for the new serial number.
Of, you could just not worry about it because it's purely cosmetic.

[dchang0]

Leave it alone and shoot the heck out of it. My lowers have scrapes and scratches all over them, so a cosmetic blemish is meaningless in that context.

[SVT-40]

Look at it this way... Yours is "special" and one of a kind... Just like a flaw on a postage stamp or coin.....

Maybe someday it will be worth more than a "normal" lower.....

[kcstott]

You want to go through all the trouble and headache of stripping, blending in the step, and reanodizing??? I mean sure you could do it but.....

Dude leave it alone and shoot it.

[19K]

Is this a like special one of a kind lower that costs $1000's of dollars? No? Then shoot it.

[Cheep]

That should have been called a "blem" but, shoot it anyway.

[klewan]

They use acid to strip the anodizing, that will also remove metal and now everything is off spec. I don't get this obsession with every little nick or "the colors don't match"; it's like a bunch of women...

[kcstott]

They use acid to strip the anodizing, that will also remove metal and now everything is off spec. I don't get this obsession with every little nick or "the colors don't match"; it's like a bunch of women...

Well it's not acid but it is caustic and corrosive.
It's alkaline dipped and will etch all of the anodize off and it will change the dimension of the part.

See anodizing is not a coating or plating process. It's a conversion.

The layer of anodize is split along the original surface. Meaning that 50% of the thickness is in the metal and 50% is on the metal.

So if you had a 1" square block and had it anodized with a layer thickness of .001" you would end up with a part that is only .001" over size because half of that build up is in the surface.
Now if you reanodize and strip the surface first and everything is perfect you part will now be .999" if you are lucky.

Not to mention all the tolerances on the ordinance print is taking into consideration that the part will be anodized and will affect the sizes of features.

[rromeo]

Okay, where is the flaw I'm looking for?

[Syds Grandpa]

Important to know if it's hard ano. Hard Anodize is usually about .002 thick. Hard anodize penetrates as much as it build up. So the Ano will penetrate .001 and build up .001. If you strip that lower you are potentially going to open all the diameters up by .002. Not good. Go shoot it and leave it the way it is. Also, that's a bad spot to blend when machining lowers.

[mindwreck]

ask for some money back and just shoot it... not worth the trouble to machine and anzodize or redrosing new ones.

[semperfi24]

I looked at my lowers after reading this thread and they are the same as yours. They are from different manufacturers Mega, RRA, Riflegear, Franklin armory. I don't think it's a flaw, if I had to guess I think it would have something to with with leaving some extra material for strength on the takedown spring.

[thatsteveguy]

Well, I looked at my other billet and there isn't that "line" and there's gobs of material for strength for the takedown spring. I went online and found some photos of lowers made by the same company posted by their owners. Would you believe it, that line is on their lowers too! The serial number on mine is less than #1200 and the serial #1 lower shown on their FaceBook page showed the same "flaw". My question is; if your programer can get the CNC machine to blend one side, why can't he blend the other side. For the life of me I can't figure out why a company would knowingly anodize and release incomplete work! Anyway, I've cooled down and will take the advice of the CalGuns input and just finish building it and shoot it.

[bohoki]

see if you can get a partial refund for your trouble and live with it