Soft Norinco Reciever?

J

jackdoac

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Ok, first don't beat me up too bad if this is a dumb question but here it goes:

I have a new 2007 Norinco M14, and, as a quick test of receiver surface hardness I ran a triangular file over a discrete location expecting it not to catch but lightly skim over. Unfortunately, it did easily catch and remove material (metal, not parkerization).

I also have a garand and when I duplicated the test with it (same pressure, file, etc) it did skim over the reciever as expected.

What's the deal?
 
I guess what I'm asking is if the receiver is supposed to be that soft?

If it isn't (which I bet is the case) is there any place in Canada that can do a proper heat treat of an M14 reciever (and for how much)?
 
Well, technically speaking, there are very soft steels which have surprisingly adequate tensile strength... but in all honesty, it's probably just a screw-up in hardening the thing.

I'm sure if you ask around at local metal or tool shops they'll know of a metallurgical shop which does said treating. If they have to do a full diagnostic to figure out the type of steel they're working with, it may not be the cheapest thing ever.

-M
 
Do you know how a M305 receiver is suppsed to be hardened? It is supposed to be the same hardness everywhere? Why not try your same test in a locking area?
If you are serious about determining information about heat treatment, have a properly equipped test faciltiy do some tests with a machine intended to produce Rowckwell readings.
Carefully inspect the receiver - are there any tiny pinprick marks to be seen?
A skating file can tell you if something is surface hardened, or if something is glass hard all the way through. Would either of these possibilities reasssure you about the condition of this receiver?
 
I'm not sure about if m14 recievers are hardened in a uniform way but given the close relation of the m14 and m1 I would say that they should be similar.

As for pin pricks, there dosen't appear to be any (what is this a check for?).

It may be worth getting a quick rockwell check done but I'm not really sure how hard it should be (maybe around a 55?).

As for the type of steel the reciever is composed of, I have read that destructive testing of American Norincos were an equivalent to 8620. I'd assume that they would not have changed compositions (but you know what they say about guys who assume).
 
jackdoac said:
As for pin pricks, there dosen't appear to be any (what is this a check for?).
Click to expand...

A pin-prick is a mark left by a Rockwell hardness-tester.

Likewise, it may have been tested for hardness with another machine, using a hardened ball; look for small ball indents if any.

Regardless, taking it somewhere for a quick test could save a bunch if the locking area (for example) is induction-hardened rather than having the whole receiver hardened via a 'soak' process.

-M
 
Is it typical for only high wear areas to be hardened?

Can you do induction heating to carburize a part (as I think the recievers are meant to be case hardened only)?

I guess I'll have to have the damn thing hardness tested, doh.
 
yes, it is typical that only certain part of a piece are hardened...speaking in general....I don't know about the norc receiver.

dont forget that as the hardness rise....the britelness rise also.....

what it means that it is possible to treat only one portion of a piece for high wear areas...and keep the material less brittle every else. It makes the material keep its elasticity and more resistant to fatigue wear.

Take for example a file. the material is realy realy hard on these....but also realy brittle. take one and bang it flat againts a table. it will break for sure (britelness). but try to make a dent in it with a punch and hammer......you will have a hard time doing it!

at the other end, take a piece of regular 1020 steel ( soft machineable steel). You will be abble to make a dent verry easely on it ( softness)...but bang it flat agains a table.....and keep going at it all day...it will take a verry long time before its breaks apart!
 
M14 receivers are supposed to be case hardened, throughout not induction hardened in "specific" spots. So they should have a hard surface throughout and a softer flexible inner core.

I got the numbers somewhere around here but can't find them right now. I'll see if I can find them after work.

Dimitri
 
M14 Receiver Hardness Requirements - USGI receiver drawing 7790189 requires a surface hardness of 56 to 60 HRC and a core hardness of 28 to 42 HRC.

The receivers SHOULD be made with 8620H. So they must be case hardened to harden at all. Not enough carbon content.

Dimitri
 
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Buckbush,

Perhaps they are, I was stating what is spec for the M14, just because the Chinese decided to use something else (which isn't surprising at all) means nothing to me.

Dimitri
 
Guns with aluminum receivers have bolts lugs which lock into the barrel, not the receiver (AR15, XCR, etc).

An m14's locking lugs are in the receiver and are high stress areas which would be worn down quickly if the steel is not properly hardened (quickly causing excessive head space).
 
Michael,

Jackdoac is right, most guns with aluminum and even plastic receivers have inserts to deal with the pressures.

All the pressure of a AR-15 is in the barrel, bolt and the locking ring. The receiver could almost be made with wood on a AR-15.

Dimitri
 
buckbrush said:
Norincos are not made of 8620h, they are made of a 5000 series steel, and test at the low 40's Rockwell c. Use the search function.
Click to expand...



I can't seem to find this post (regarding the Norinco steel type) using the search, could someone please post a link or something?
 
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