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Old September 09, 2019, 16:48   #1
keysort
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Receiver Hardness?

I'm modifying the Garand receiver for a BM-59 build. At this point, it's ready for heat treating, but I can't seem to find reliable information on the correct hardness. I'm using a cast 4140 receiver, and the heat treater I've contacted said he usually through hardens receivers to 42-44 RC, but he can go up to 50-52 RC.

It seems like Norinco made M14 receivers that were around that hardness, but do you know if they were through hardened, case hardened, etc?

I'm far from a metallurgist...hopefully someone here can educate me!
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Old September 09, 2019, 18:25   #2
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I know they cannot be "hard" all the way through, hard like Rockwell 60 -> 62. It will turn them into a grenade, very unhealthy. I'm hoping an expert will give you "The True" specs, but the inner treatment should be around 30 or so and it gets harder at the surface, like around 58 -60 at .018" deep?

Go to The M-14 Forum and ask over there. They have guys that make the M-14 receivers and know EXACTLY what to do. Heat treating a firearm receiver is best left to the experts.

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Old September 09, 2019, 18:44   #3
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Old September 10, 2019, 04:55   #4
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I would expect different specs at different times

Different steel grades were used at different times for the M1 receiver, and quenching & tempering will give you different hardnesses and different microstructures. For something like a firearm, if you have the right hardness but wrong microstructure, you still have a bomb.

Hatcher's Notebook apparently has a lengthy discussion on the M1 receiver, but my copy is downstairs and I don't have time to go get it until later.

The M1 receiver was apparently carburized, as you'd expect.

I found the following on line: https://m1-garand-rifle.com/history/...eld-armory.php

I would look to see if you could find anyone who had welded M1 receiver halves back together, and see if you could learn anything from their experiences heat treating after welding.
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Old September 10, 2019, 05:29   #5
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Ive no direct knowledge, but Ive a friend who's built a few bm59's and Im about 100% sure he never needed to send them out for rehardening.
How did you 'modify' it that would have effected the heat treatment it started with ?
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Old September 10, 2019, 11:04   #6
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Quote:
Originally Posted by Democrat1 View Post
Different steel grades were used at different times for the M1 receiver...............

Quote:
Originally Posted by yovinny View Post
Ive no direct knowledge, but Ive a friend who's built a few bm59's and Im about 100% sure he never needed to send them out for rehardening.
How did you 'modify' it that would have effected the heat treatment it started with ?

New receiver, guys-

Quote:
Originally Posted by keysort View Post
I'm modifying the Garand receiver for a BM-59 build. At this point, it's ready for heat treating, but I can't seem to find reliable information on the correct hardness. I'm using a cast 4140 receiver, and the heat treater I've contacted said he usually through hardens receivers to 42-44 RC, but he can go up to 50-52 RC.
Keysort-

Is this a receiver from the SARCO sale ?


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Old September 10, 2019, 11:12   #7
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So this is an unfinished garand casting then ?
My bad,,I thought it was an actual garand receiver....
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Old September 10, 2019, 16:36   #8
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Could always ask Shuff, he builds them
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Old September 10, 2019, 17:19   #9
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It wasn't the SARCO receiver. It's an older one I picked up cheap on gunbroker. Everything seems to fit together just fine.

Thanks for the advice, I'll consult the M14 Forum, but feel free to chime in with any more info!
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Old September 10, 2019, 20:41   #10
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The ones Sarco sold were labeled Foster Industries on left front side.They claimed they were 4140 and they had their own mold which I believe is for sale.

I used ADI Lithgow castings from Numrich which were leftover SAI inc Garand receivers.They are 8620 Alloy which is correct metal.


Both 8620 and 4140 can be through hardened but carburizing was the original method . original specs were carburize to .012" - .018" deep surface hardness was measured with D scale D61 - D71 which is app.
48 - 60 HRC. Core 28 - 42 HRC

Most measure at 58 - 60 HRC. On surface

Anything 4140 will have to go through vaccumn furnace
Nitriding may also be possibility.
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Old September 12, 2019, 07:03   #11
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I'm not sure what sort of life a 4140 casting will give you, and there's no spec because no GI Garand receivers were that grade of steel. The earlier receivers were 'War Department 3115' then 'War Department 3120' followed by the change to 8620 around serial 600,000.
The earlier rifles had an over-hardening issue that resulted in the 'lead anneal' technique being used to 'soften' the heel - resulting in a two-tone receiver that's highlighted if zinc phosphating is used.

Eli

Last edited by AliYahu; September 16, 2019 at 06:54. Reason: typo
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Old September 12, 2019, 07:31   #12
Pat C.
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Nitriding is the only way one would last and work close to design. If You were to thru- harden the receiver I wouldn't go much above mid 40's HRC which will be above max core hardness which was 42 HRC

4140 great for parts that are beefy and can be post heat treat ground / machined. The various thickness cross sections of the M1 receiver is not ideal for that.

If you thru- harden into low 50's HRC you are asking for trouble.Still have no idea why SARCO would have used 4140.

If you have the pieces left from cutting the legs to BM59 you can have them tested using spectroscopy from or just have a heat treat facility try to carburize one piece using original callout .

If they carburize it to print you can carefully mill the section on one end using carbide or surface grinder so the core is exposed for rockwell testing of core and case.

As I said before probably safer to have it nitrided ,
Flame and induction hardening is common for 4140 but NO way M1 type receiver would stay straight for that.

All three of my receivers were done in vaccumn furnace with integral quench.There is a heat treated that specializes in all types of heat treat including Nitriding and carburizing and they have FFL ,give them a call.
AHT Corp .com
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Old September 15, 2019, 17:07   #13
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Great information, I really appreciate it.

To make sure I understand correctly, do you think the receiver only needs to be nitrided? Is through-hardening only necessary if the receiver tests below a certain hardness?
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