Metal Injection Molding or Casting Impressions in the Metal

BigGameHunter

BigGameHunter

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I have noticed on my Norinco M4 on the side of the upper where the rectangle (don't know if there is a name for it but its the opposite side lines up with the Bolt), that there is a depression in the Aluminum. It is not big or deep, the paint is not chipped so it was done while it was bare metal, I am just wondering if it is a big deal or if it is common with Cast, MIM (which I believe the upper is) parts to have this. I asked my father and he said it is probably where they separated the material from the mold but I just wanted to make sure. It is about 6mm in diameter and about (just guessing ~1mm or slightly more deep).

If it is just a cosmetic thing that I could care less. I just want to be 100 percent sure that there is nothing structurally to worry about. I don't shoot it often and have only shot it once without problem but I just would like to confirm that it is not something I will have to worry about in the future.

Anyone else have one of these marks? Thanks. If you want I can take a pic but in low light you can really see it you can only feel it or if I am able to get a pic when it is bright I will. Thanks for anyone who can put my mind at ease or inform me as to what causes that as you guys seem to know much more with regards to metallurgy and Black rifles than I but I am trying to learn.
 
Pics removed as they were wasting time loading for slower connections. At least I am considerate if a bit gun illiterate. HAHA
 
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A clearer picture full gun not as noticeable

Close up but starting to get blurry. Hard to get a shot that does the imprint justice but you can see its not cracked and just a circular imprint there is also very small bottom portion of the imprint that looks larger due to the lighting but this is the most accurate one i think. I really appreciate your guys help. I think it is just what you pay for with norinco, you get little cosmetic glitches but when i fired it it felt and functioned just fine.

 
Good pics - helps clear things up for sure.

Just a casting defect, probably outgassing from the mold. Not an issue at all structurally.

-M
 
Thank you sir. See its stuff like that I would only learn here or if I took a gunsmiths or metallurgy course. Glad to hear it. Now I cant wait to shoot it since I put on the new front end.:D
 
Now I am confused. In this post I received replies that this frame was cast, injection molded and forged. For reference the Wikipedia page on this type of rifles says they are T6 aluminum that is MIM which I thought was somewhere in between cast and forged in terms of strength, quality but fast and cheap like casting.

Sorry If I am incorrect the manual does not tell you these things. It just talks about annihilating firepower.

I guess it doesn't really matter I am just trying to learn this stuff. Thanks though.
 
I wonder why it would say that? So its forged then?

Here is what wikipedia said (I know they are not the be all end all but lots of information, maybe too much)

"While the American AR-15/M16 rifles are built in T70-74 aluminum, the Chinese Type CQ is built in T60-60 aluminum, used to allow the process of Metal Injection Molding to be used instead of forging"

Anyways if you could point me in a direction that can give me more detailed information with regards to this gun more where you guys got your information from besides here. Like I said the Manual doesn't say and I have looked all over the internet and have not found these details except what I quoted above. That you for the information though as like I said with Black Rifles I am still learning and hope to continue learning as much as possible.
 
on the case deflector,i have grind marks under the annodizing.there are some other grinding/dremel marks elsewhere also.it kind of looks like extra material was ground off and not too gently.i'm not complaining,it won't affect function,only looks...
 
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