HKPRO Forums banner
1 - 20 of 28 Posts

·
Registered
Joined
·
116 Posts
Discussion Starter · #1 · (Edited)
Update: For those still interested, Mr. Sam Bass of HK kindly replied to my email inquiry. Mystery solved! Thanks everyone.

YES. What you are seeing is actually residual from the laser hardening process on the leading edge of the slide.
All other markings are normal wear marks from function (proof/test firing).
If you have any other questions or concerns, please let us know.


Hi all, just got my first HK, a NIB BD date code HK45c. During the first cleaning, I noticed the slide had faded white lines unlike typical silver colored wear marks. They remind me of hamon lines on differentially tempered swords. Are the white lines from spot heat treatment? Please consider that I'm asking out of curiosity, not out of dissatisfaction or complaint.
 

Attachments

·
Registered
Joined
·
6,711 Posts

That is completely normal. The pictures I took are from a BD with about 3 to 500 rds through. When they test fire at the factory , the slide and barrel cycling creates what you are seeing. I sometimes have had a little brass mark on the ejection port face .
Congratulations on your purchase. You chose a fine pistol . Enjoy !

Hopefully you can see the pictures.
Sent from my SCH-I605 using Tapatalk 2
 

·
Registered
Joined
·
275 Posts
The slides are heat treated throughout. My GUESS is that they're machined after heat treat. What you're seeing is some finish wear at some metal-to-metal contact points
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #4 ·
Thanks for the kind words. It's my first polymer handgun. Decided if I was going to go plastic, I might as well get the best! Loving the ergos so far.

If you look closely at the first photo, the faded white line I'm talking about is above the silver wear mark where the barrel lug contacts the slide. Since the white mark is above where the barrel contacts the slide, I'm not sure how it would form during test firing. But I'm open minded and curious, so keep the comments coming.

That is completely normal. The pictures I took are from a BD with about 3 to 500 rds through. When they test fire at the factory , the slide and barrel cycling creates what you are seeing. I sometimes have had a little brass mark on the ejection port face .
Congratulations on your purchase. You chose a fine pistol . Enjoy !

Hopefully you can see the pictures.
Sent from my SCH-I605 using Tapatalk 2
 

·
Registered
Joined
·
6,711 Posts
You might want to research the Carbon Nitriding process . To apply that "finish" if you will, the whole part is heated to around 1100 degrees during the process . Even though you see steel , it is still has protection .

This is done after machining .I'm not a chemist but there are salts involved in the process .
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #6 ·
Not worried about corrosion, since those areas will have lubrication. Did some reading and found that nitrocarburizing has a case hardening effect in addition to protection against corrosion. Case hardening would reduce surface wear, but compression strength is needed for slide lug longevity since we are talking about impact force from the barrel lug. Just guessing here, but maybe HK spot hardens the slide lug at some point (and at other locations).

You might want to research the Carbon Nitriding process . To apply that "finish" if you will, the whole part is heated to around 1100 degrees during the process . Even though you see steel , it is still has protection .

This is done after machining .I'm not a chemist but there are salts involved in the process .
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #7 · (Edited)
Thanks for the reply. I also thought it was metal to metal contact wear, but in the first photo (of the slide lug), the location of the white mark is above the highest point the barrel lug can go. In other words, the white markings on the slide lug are above the reach of the barrel lug.

The slides are heat treated throughout. My GUESS is that they're machined after heat treat. What you're seeing is some finish wear at some metal-to-metal contact points
 

Attachments

·
Registered
Joined
·
6,711 Posts
I'm not sure what your point is .Are you talking about the barrel or the slide ? I don't see why they would " spot harden" anything . The breach face and the recoil spring/assembly takes the mechanical load . The barrel "lug" goes in to the recoil spring assembly and pulls the barrel down and out of the way of the slide . The slide starts as a forging , this isn't some BS casting or bar stock material. It's a very good topic ( the HK process) to research if you have some time. Enjoy !
 

·
Registered
Joined
·
818 Posts
The Tennifer or Melonite by name nitrocarburizing makes the metal so hard, the only thing that will cut it are diamonds or a grinder. I had a German gunsmith show me how hard it makes the steel. He had an original MG 42 machine gun barrel. Put it in a vice & bet me $10 I couldn't mark it with a right out of the package Mill file. Try as I may, the file just skated across the barrel. THAT IS SOME HARD STUFF !!!
 

·
Registered
1997 USP 9mm Full Size, too many upgrades to list.
Joined
·
610 Posts
It's just wear marks, while the barrel lug certainly doesn't go that high, but any lube on the slide/barrel will spread on the impact.

Every shot impacts this way, not just the test fire, or did I miss something and this pistol is unfired?


Typoed on my iPhone.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #11 ·
I don't doubt the entire slide is through hardened. Was just wondering if HK did some additional spot hardening to strengthen the parts of the slide shown in the photos. I don't think the white marks are caused by metal to metal contact because at least in the first pic (slide lug), the barrel doesn't go up that high. Tomorrow, I'll try to get a photo of the area with the barrel in battery.

In addition to the breech face and recoil assembly, the slide lug and the barrel's upper lug also take a mechanical load. I'm talking about the barrel's upper lug that mates with the slide lug, not the lower barrel lug that mates with the recoil assembly. At the time the primer ignites to the moment the bullet leaves the barrel, there is extreme force between the barrel lug and the slide lug. The casing is pushing the slide back but the bullet is trying to pull the barrel forward. My point was that nitrocarburizing is a surface hardening process, which would reduce surface wear but perhaps the area was also spot hardened to deal with the tensile force between the barrel upper lug and slide lug. Surface hardening would do nothing to lengthen the lifespan of areas that see tensile/compression forces.

I will do that, research HK slide forgings, thanks for the suggestion!

I'm not sure what your point is .Are you talking about the barrel or the slide ? I don't see why they would " spot harden" anything . The breach face and the recoil spring/assembly takes the mechanical load . The barrel "lug" goes in to the recoil spring assembly and pulls the barrel down and out of the way of the slide . The slide starts as a forging , this isn't some BS casting or bar stock material. It's a very good topic ( the HK process) to research if you have some time. Enjoy !
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #12 ·
From what I've read today, the process is indeed as amazing as you say. However, it is important to note that it is a surface hardening. Meaning it will do nothing for tensile/compression forces. Image nitrocarburizing a block of steel that is only moderately hardened, say 20 RC. The block will be 20 RC throughout, except the surface, which will be around 70 RC. Take a file to the surface of the block and there will be no scratches. Then take the same file to a through hardened block of steel at say 50 RC. There will be scratches. Now take a hammer and whack both blocks. The nitrocarburized block will more likely dent compared to the 50 RC hardened block.

The Tennifer or Melonite by name nitrocarburizing makes the metal so hard, the only thing that will cut it are diamonds or a grinder. I had a German gunsmith show me how hard it makes the steel. He had an original MG 42 machine gun barrel. Put it in a vice & bet me $10 I couldn't mark it with a right out of the package Mill file. Try as I may, the file just skated across the barrel. THAT IS SOME HARD STUFF !!!
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #13 ·
Thanks for the comment. Pistol is unfired except for the factory test shots. The white marks are not caused by lube, I've already cleaned any factory grease/lube off.

It's just wear marks, while the barrel lug certainly doesn't go that high, but any lube on the slide/barrel will spread on the impact.

Every shot impacts this way, not just the test fire, or did I miss something and this pistol is unfired?


Typoed on my iPhone.
 

·
Registered
Joined
·
15 Posts
HiPower,

You're good to go my friend. What you're seeing there is completely normal. It's easy to get fixated on something! I speak from experience Sir! But when you bought a HK, you invested in the best. Use with confidence!!!
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #15 · (Edited)
HiPower,

You're good to go my friend. What you're seeing there is completely normal. It's easy to get fixated on something! I speak from experience Sir! But when you bought a HK, you invested in the best. Use with confidence!!!
Thanks for the kind words. Just to clarify, there's no problem here. Reason I bought a HK is because of their stellar reputation for quality, so I'm not worried at all. I'm asking out of curiosity, because I consider myself a fan and student of machines.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #16 ·
Here is a photo of the hazy marking on the slide lug, with the barrel in battery. The haze is above the portion of the slide lug that makes contact with the barrel lug.
 

Attachments

·
Registered
Joined
·
485 Posts
In the gun business we call that "normal" wear patterns. Like others have said, completely normal, nothing to worry about if you are actually going to shoot your guns.
 

·
Registered
Joined
·
275 Posts
YES. What you are seeing is actually residual from the laser hardening process on the leading edge of the slide.
All other markings are normal wear marks from function (proof/test firing).
If you have any other questions or concerns, please let us know.

A laser hardening process?! I am surprised!
 

·
Premium Member
Joined
·
3,020 Posts
Yup. I came across a thread on a different forum where someone's USP 9 slide cracked after use with a suppressor. Upon receipt of the broken pistol, H&K was shocked to find that the slide had left the factory without being laser hardened at all, causing it to fail. Oops! They ended up replacing the pistol.
 
1 - 20 of 28 Posts
Top