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Discussion Starter · #1 ·
OK, so I emailed HK USA about 5 months ago and called a few time, and it took about 4 months for them to get back to me about this.

I asked them if the bore on the MR556 had any coating on it, they reassured me it indeed was nitrided as all their barrels are. Then I think it was Grumpy who mentioned that the MR556 barrel was not nitrided, so is there any real proof of whether the barrel is indeed nitrided or not. Just seems odd for HK to lie or to not know.
 

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I was wondering this as well as I came across something similar regarding HK barrels. I wish I could remember the source, because they said the factory barrels are nitrided.

That said, Sinless, while your post raises a fair question, what's the point of the last sentence?
 

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Discussion Starter · #3 ·
I was wondering this as well as I came across something similar regarding HK barrels. I wish I could remember the source, because they said the factory barrels are nitrided.

That said, Sinless, while your post raises a fair question, what's the point of the last sentence?
Well Grumpy said the barrel was not coated with anything, which is why he got it nitrided. Yet HKUSA told me ever single barrel was nitrided, my point is who is correct? If Grumpy is correct(which I have no reason to doubt him) then why would HK tell me all barrel are nitrided? is it that they do not know or did not tell the truth. It was just a harmless sentence.

I mean I would expect for HKUSA to know and tell the truth about their barrels.
 

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Fact: Nitriding steel increases the hardness of the base material to near/equal/in excess of Chrome hardness depending on the alloy.

Fact: Milling on a nitrided piece of steel needs a carbide bit to get past the surface treatment without damaging the bit.

Fact: I used a standard HSS lathe bit and did all of the work to my own barrel just fine. No carbide bit necessary.

You do the math.

I think someone at HK is getting their terminology mixed up. They parkerize their barrels, but they still remain un treated/non-nitrided.
 

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Fact: Nitriding steel increases the hardness of the base material to near/equal/in excess of Chrome hardness depending on the alloy.

Fact: Milling on a nitrided piece of steel needs a carbide bit to get past the surface treatment without damaging the bit.

Fact: I used a standard HSS lathe bit and did all of the work to my own barrel just fine. No carbide bit necessary.

You do the math.

I think someone at HK is getting their terminology mixed up. They parkerize their barrels, but they still remain un treated/non-nitrided.
You omitted one small, tiny detail.

Barrels are nitrided in Germany. But they came to USA as unfinished barrel blanks. Then they are profiled, fitted barrel extension, drilled gas port and externally finished at Daniel Defense. This process makes them "USA made barrels". But in the process external, hardened (nitrided) layer of barrel vanishes in form of steel shavings. Nitriding remain only in barrel bore.

You do the math.

So both of you and HK are right at same time.
 

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Discussion Starter · #6 ·
You omitted one small, tiny detail.

Barrels are nitrided in Germany. But they came to USA as unfinished barrel blanks. Then they are profiled, fitted barrel extension, drilled gas port and externally finished at Daniel Defense. This process makes them "USA made barrels". But in the process external, hardened (nitrided) layer of barrel vanishes in form of steel shavings. Nitriding remain only in barrel bore.

You do the math.

So both of you and HK are right at same time.
Excellent iformation, honestly the chamber and bore is all that really matters.

How did you find out they are nitrided as blanks?
 

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Excellent iformation, honestly the chamber and bore is all that really matters.

How did you find out they are nitrided as blanks?
"All their barrels are" - this mantra comes back all the rime. Nitriding is standard process at Oberndorf for barrels, slides, etc (actually it is standard for some other European manufacturers who make military firearms). "Uncoated" MR223 barrels are nitrided (because nitriding is not considered "coating"). Why would HK omit this standard step for MR556 blanks (would they make them lesser than MR223)? And, if those would be nitrided in US, we all would now this long ago. But long time to get answer suggests that HK USA needed to confirm this with HK Gmbh (and getting answers from them is long and painful process - belive me). So all fingers point at Oberndorf as place where nitriding occurs.

Sometimes hard evidence is not needed, long list of clues that fall into logical process can be enough.
 

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I don't see it as being true.

It would be incredibly hard on the tools at Daniel Defense if they had to machine nitrided steel.

Is this something that can be checked with a hardness meter?

-W
Other factories I know manage to work on nitrided steel. You just need to use right tools. In era of PVD tool coatings, HSS seem like using flint hammer.

Besides, why would HK USA lied? Initially they were answering that barrel is not coated (it is true) but they could not say if it is nitrided or not. Sales guys sometimes do not know technical details, or even do not understand them. But looks like they had so many people asking this question, so they decided to learn about it. If it was not nitrided, all they needed to do is remain tight lipped.
 

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Yea, um....no.

I also polished my chamber prior to nitriding and hand lapped the bore.

No nitriding otherwise the hand lapping would have taken more then an hour to do.

The barrel blanks are NOT nitrided in Germany prior to being sent to the US and while people do "manage" to work on nitrided steel, it is not ideal, nor is it something that is done as a normal course of business.

I stand by my statement that the folks answering the questions are mistaking the processes that are applied to the parts and are not doing their homework.
 

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They may be. There are plenty of differences between the European version and the US version.

Another thing to consider is the oxidization layer that is built up on the surface of the steel when nitrided. When the oxygen is displaced by nitrogen and carbon in the surface of the steel, the material forms a layer of an almost rust like nature that MUST be removed from the inside of the bore before shooting. This would be another tedious step that HK or DD would have to perform on every single barrel that has been nitrided.

I know that Sig nitrides their barrels and does this, so it's not out of the realm of possibility that HK does it.

But given the totality of my experiences thusfar with my MR556, I'm still inclined to believe that the US version is in fact not nitrided.

Although I will say that after nitriding, I found the bore much easier to clean out of the oxydization layer then I was lead to believe by my research. This could have been for a number of reasons though. Hand lapping the bore was as easy as any other gun (a sign of no nitriding) and polishing the chamber was as easy as any other rifle(also a sign of no nitriding), and for all I know, H&M could have cleaned the bore for me prior to sending it back to me. All oxydization was removed from the parts when I recieved them in the mail, so i'm inclined to think that H&M did it rather then say that the bore was already nitrided and thusly wouldn't build a second oxydization layer.

Well, I should say a third oxydization layer as I did the QPQ (quench-polish-quench) process which double dips the parts with a ceramic bead blast inbetween to remove the oxide and gain a greater penetration on the second dip.

edit to add: RE:eek:xydization caused by nitriding needs to be removed for best performance of the parts. If it is left, the part will easily develop rust, which leads some to believe that nitriding is a scam. The fact is that it's merely the oxydization layer that was left behind that is rusting, not the part itself. Remove the layer and the materiel below is fine.
 

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Personally I would like to know the resolution to this as well since I now own one. I would agree that salesman/phone answerers at HK could certainly be mistaken about the process. If it's not on the screen in front of them and they don't take the time to actually chase down the facts they may very well be wrong in their answer, this is not unusual.

Barrels are nitrided in Germany. But they came to USA as unfinished barrel blanks. Then they are profiled, fitted barrel extension, drilled gas port and externally finished at Daniel Defense.
If this is in fact the case, then I would ask why doesn't someone call DD and ask since they are the ones supposedly working on them. I would assume they are certainly smaller than HK so it may be easier to get an informed response.
 
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