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Bula Forge case thickness, case hardness and core hardness

This is a discussion on Bula Forge case thickness, case hardness and core hardness within the Reference forums, part of the M14 M1A Forum category; The purpose of this post is for informational purposes which I'm passing along as I obtain relevant information. I was talking with Jeff yesterday about ...


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Old March 17th, 2017, 06:29 AM   #1
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Lightbulb Bula Forge case thickness, case hardness and core hardness

The purpose of this post is for informational purposes which I'm passing along as I obtain relevant information.

I was talking with Jeff yesterday about case thickness of his receivers and bolts. He told me that they sacrifice a piece out of each lot of receivers and other parts to test case hardness/thickness and core hardness. Because he has a government contract to supply the .GOV with M14 parts, he is required to have his parts inspected per government guidelines. If I have mis-stated, I'm sure Jeff will correct me.

For those who don't know, the case thickness spec of a receiver and bolt is 0.012" to 0.018" thick. Jeff told me that the average case thickness is from lot to lot is between 0.014" to 0.018" thick.

Core hardness spec is 28 to 42 HRC, while surface hardness is 68 to 71 HRD.

With Jeff's permission, here is an example of one of their receivers that was destroyed and the kind of inspection that is performed. The example is of a past lot and I don't know the timeline of when the picture was take. It may or may not be representative of current lots that are being sold.

Tony.
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Old March 17th, 2017, 07:59 AM   #2
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Thanks Tony and Jeff.
PROPER heat treatment of the M14 receiver is a critical and often overlooked factor with too many aftermarket manufacturers. Of course the iriginal US GI receivers set the Gold standard, and it is great to learn that BULA is meeting these standards.

For decades I have been working with the ubiquitous Chinese/Canadian M14 receivers, which by my personal experience, usually have excellent receiver geometry, but which MAY vary considerably regarding heat treatment and hardening. I have seen several that were too soft for long term durability, and one that was definitely too hard and brittle ( it broke off a leg when it fell off a bench on to a concrete floor).
Is there any chance BULA might consider re-heat treating other brands if receivers as a customer service??
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Larry Z

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Old March 17th, 2017, 09:56 AM   #3
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Originally Posted by Lazerus2000 View Post
Thanks Tony and Jeff.
PROPER heat treatment of the M14 receiver is a critical and often overlooked factor with too many aftermarket manufacturers. Of course the iriginal US GI receivers set the Gold standard, and it is great to learn that BULA is meeting these standards.

For decades I have been working with the ubiquitous Chinese/Canadian M14 receivers, which by my personal experience, usually have excellent receiver geometry, but which MAY vary considerably regarding heat treatment and hardening. I have seen several that were too soft for long term durability, and one that was definitely too hard and brittle ( it broke off a leg when it fell off a bench on to a concrete floor).
Is there any chance BULA might consider re-heat treating other brands if receivers as a customer service??
Thanks
Larry Z
Re-heat treating rarely ever works out well.

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Old March 17th, 2017, 10:01 AM   #4
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Originally Posted by tonyben View Post
The purpose of this post is for informational purposes which I'm passing along as I obtain relevant information.

I was talking with Jeff yesterday about case thickness of his receivers and bolts. He told me that they sacrifice a piece out of each lot of receivers and other parts to test case hardness/thickness and core hardness. Because he has a government contract to supply the .GOV with M14 parts, he is required to have his parts inspected per government guidelines. If I have mis-stated, I'm sure Jeff will correct me.

For those who don't know, the case thickness spec of a receiver and bolt is 0.012" to 0.018" thick. Jeff told me that the average case thickness is from lot to lot is between 0.014" to 0.018" thick.

Core hardness spec is 28 to 42 HRC, while surface hardness is 68 to 71 HRD.

With Jeff's permission, here is an example of one of their receivers that was destroyed and the kind of inspection that is performed. The example is of a past lot and I don't know the timeline of when the picture was take. It may or may not be representative of current lots that are being sold.

Tony.
Well, he only has to have parts intended for sale to the Government inspected per Government standards, for parts intended for commercial sale only he could theoretically inspect them any way he wants.

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Old March 17th, 2017, 10:16 AM   #5
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Well, he only has to have parts intended for sale to the Government inspected per Government standards, for parts intended for commercial sale only he could theoretically inspect them any way he wants.
I have a sneaky suspicion that Jeff wants ALL his products to meet the proper standards for his own peace of mind. Just my 2 pennies...

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Old March 17th, 2017, 10:40 AM   #6
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I have a sneaky suspicion that Jeff wants ALL his products to meet the proper standards for his own peace of mind. Just my 2 pennies...
I wouldn't doubt it for a minute, why risk a reputation for a few pennies.

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Old March 17th, 2017, 11:34 AM   #7
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I've been to their production site. I can tell you they are top shelf in R&D and manufacturing. Retiring from the semiconductor company, it is quite a contrast between it and a forging operation, but the manufacturing quality systems in place are the same.

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Old March 17th, 2017, 01:19 PM   #8
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What I posted originally was not intended to be a dig against Bula, or their quality, but just an observation about production processing.

At one point in my career, I worked at a raw plastic manufacturer, they made the raw plastic beads that were melted down by their customers to made all manner of plastic stuff. The actual process used to make each formulation never changed from batch to batch, but the required quality assurance paper trail for each customer was different.

If we were going to make a lot of recipe "A", the operator flipped the binder open to recipe "A" and followed the directions to make that formulation, how the ingredients were measured into the hopper, mix times, bake times, they never changed. Some customers didn't care at the raw material was bagged and shipped as it came out of the dryer. Some customers wanted a batch sample tested, so someone took a scoop of stuff over to the lab and got a print out of how well it met the recipe "standards", and that sheet was send out customer, Some customers wanted that test sheet done for each 500 pounds out of the dryer, so the lab ran a test four or five times that run. Some customers required the start and stop times of each section of the process to be logged and forwarded to them with the product.

Did the guys that bought the cheap stuff with no test sheet get an inferior material? No. I never saw a batch rejected for not being up to snuff, the production process was good enough to assure it always worked, but, they paid less for it.

If a good company with good processes, halves, or quarters the number of samples tested, most times the customer does not get an inferior product.

Oh, and generally, Government purchasing quality assurance requirements are specified in the contract, so what's required today may not be what's required in the next contract.

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Old March 17th, 2017, 01:45 PM   #9
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Well, he only has to have parts intended for sale to the Government inspected per Government standards, for parts intended for commercial sale only he could theoretically inspect them any way he wants.
I am pretty sure he isnt running seperate production lines.

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Old March 17th, 2017, 03:02 PM   #10
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I am pretty sure he isnt running seperate production lines.
Inspection is post (item) production. Varying the amount and rigor of the inspection process, namely the destructive type of inspection, can be done independent of the actual making of parts. See above for an example.

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Old March 17th, 2017, 07:42 PM   #11
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Core hardness spec is 28 to 42 HRC, while surface hardness is 68 to 71 HRD.
Just another note:

The surface hardness tells you how well the parts will resist wear, the core hardness tells you how strong and tough the part is.

Just about every heat treated part gets a hardness test on the surface hardness, and that gives a fair indication if the heat treating process is being done right, but to actually confirm the core is of the proper temper, you have to cut a part in half and test the hardness in the center.

For an HRc of 28 to 42 the ultimate tensile strength of the core should be 145,000 to 185,000 psi (assuming AISI 8620 steel).

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