Possible Hairline Crack?

[urge]

Noticed this on my AR15's upper receiver a couple of days ago. If it is a scratch i dont know what it would be from, and if it were a crack i dont know what itd be from. If no one here knows I will take it to someone who will, just want your opinions on the matter.
You can see it moving from the bottom of the guide rail all the way to the cam pin notch for the BCG.

http://i1101.photobucket.com/albums/g439/urge69/2012-08-27103604.jpg

 

[warbirdlover]

Take it to some heat treating place (with a metal lab). They usually all have a dye kit that reveals cracks and it's harmless to the metal.

http://www.drillspot.com/products/283771/magnaflux_sk-416_dye_penetrant_kit

If it's got a crack this will show it. Other ways are ultra sound testing but not easy to find someone that has one.

 

[mete]

Looks like a scratch but you could calm yourself by having a lab or welding shop use dye penetrant to check.

 

[big al hunter]

Find an automotive machine shop. They can magna-flux it. The magnet will not affect it and you can see the results in moments. Easier to find than most other methods too.

 

[madcratebuilder]

Spray the area with brake clean or carb clean and watch it evaporate. If it's a crack the area well stay wet while the surface around it drys.

 

[warbirdlover]

Find an automotive machine shop. They can magna-flux it. The magnet will not affect it and you can see the results in moments. Easier to find than most other methods too.

big al hunter

I've done lot's of magnafluxing and I don't know how you would hold that part (as it appears in the picture) between the copper pads and douse it with the fluid. And you have to "de-mag" it when done or it will attract every little metal chip etc. around. You also run the risk of welding some of the copper from the pads on it if not clamped tight. That's why I suggested the dye penetrant check OR a ultrasound instrument.

 

[Sport45]

I'd try Madcrate's evaporation test first. Personally, I think it's a scratch. Does it appear to go all the way through? A crack that long would just about have to.

Ask for the cost before you go to a shop and say "test it". The testing could cost more than a new receiver.

 

[Kreyzhorse]

I'd try Madcrate's evaporation test first. Personally, I think it's a scratch. Does it appear to go all the way through?

I agree with this.

 

[4V50 Gary]

Another vote for magnaflux. I also think it's just a scratch.

 

[urge]

Since the first post ive put 200 rounds through it and nothing has happened, it hasnt gotten deeper nor has it gotten longer, so i think it is safe to say it is just a scratch

 

[mete]

Told you so ! I'm a metallurgist with lots of experience in "failure analysis".

 

[ffr1910]

can you magnaflux aluminum???

 

[James K]

I had the same thought. Magnafluxing involves making magnetic poles out of the two sides of the crack; I don't see how that works on aluminum, but then I am not a metallurgist.

Jim

 

[mete]

It's got to be magnetic. So use the dye penetrant.
Magnetic particle sets up magnetic lines of force and those lines are changed at a crack ,collecting the particles. The flouresent particles show up clearly under black light.

Dye penetrant and magnetic particle tests should never be used after surface treatment like peening as this tends to cover over the cracks.Do it only before any surface treatment.

 

[TPAW]

[QUOTESpray the area with brake clean or carb clean and watch it evaporate. If it's a crack the area well stay wet while the surface around it drys. ][/QUOTE]


I like that!

 

[big al hunter]

Never played with an ar. Did not realize it was aluminium, so no, magnaflux won't work. Lots of good suggestions I would not have thought of. Learn something new every day.