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Discussion Starter #1
Does anyone have a newer 416 14.5" upper that is of a lighter profile than these who can post a photo?

I believe the 2 pictured below are the heavier ones that were refered to as "SOCOM" but from what I've read here, based on feedback from our military users, that the barrel has been profiled lighter?



The 10" versions:
The consistent profile was the earlier and the tapered is the newer version?



Hopefully some day we can see the M27 IAR barrel profile as well!

TC
 

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I want to say HKPro member "mikecleonard" has one of the lighter (govt. style) profile 14.5" uppers. Might want to give him a shout. If i'm wrong, you can blame me.
 

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I think the AH date codes and newer have the lighter profile. Every AG date I have seen has the unprofiled barrel.
 

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I want to say HKPro member "mikecleonard" has one of the lighter (govt. style) profile 14.5" uppers. Might want to give him a shout. If i'm wrong, you can blame me.
At one point I had a 10.5" upper with the lighter profile barrel...but I sold it a few years ago and never took any pictures, sorry!

In any case, the third picture down that you posted of the 10.5" barrel is the newer and lighter barrel profile...and this would look just the same on the 14.5" barrels.

If you see notches in the part of the barrel that fits under the hand-guards...then you're looking at the older heavy profile.
 

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So the "notches" were there for a proprietary barrel block system that HK used for assembling the uppers.

With the lighter profile barrels lacking the "notch", do they use traditional barrel blocks or a modified/proprietary receiver clamp block now?
 

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So the "notches" were there for a proprietary barrel block system that HK used for assembling the uppers.

With the lighter profile barrels lacking the "notch", do they use traditional barrel blocks or a modified/proprietary receiver clamp block now?
I think they just pour a couple frosty mugs of liquid awesome on it, and everything just kinda sorts itself out.

:160000:

:eek:
 

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I believe that the 10.4" with the slim profile may be an OTB barrel. I can verify with a photo of the chamber.
 

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So the "notches" were there for a proprietary barrel block system that HK used for assembling the uppers.

With the lighter profile barrels lacking the "notch", do they use traditional barrel blocks or a modified/proprietary receiver clamp block now?
Not sure how long they've been using it, but we used factory marked mandrel rods that insert from the rear and engage the lugs on the barrel extension. I'll find out if there was a previous tool.
 

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Discussion Starter #9
So the new profile looks like the tapered 10" above but with the extra 4", m203 cut, etc?

Is this profile that was cut on an MR556 not the way the new ones are profiled on the new 416 14.5" uppers?

 

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So the new profile looks like the tapered 10" above but with the extra 4", m203 cut, etc?

Is this profile that was cut on an MR556 not the way the new ones are profiled on the new 416 14.5" uppers?

Correct for your first question

The MR556 barrel pictured is close, but not exactly the same as Hk's newer profile under the hand-guard.
 

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but we used factory marked mandrel rods that insert from the rear and engage the lugs on the barrel extension.
Interesting approach. did the mandrel also prevent movement of the upper receiver or was it a straight rod with lugs on the end that matched the barrel extension?

Since all the force of the barrel nut is applied to the extension and to the threads on the upper, I personally, would feel better knowing that the upper was captured as well to help prevent any movement of the barrel alignment pin in the alignment pin slot.

The reason for my concern is that I have seen uppers ruined by incorrect torqueing of a barrel nut and inadequate lube (grease) which caused the upper to pivot around the barrel and caused the alignment pin to rotate through the softer aluminum and cause the barrel to be extremely out of alignment as well as damaging the upper.

Not saying that HK doesn't have their QC **** wired tight, but everybody has a bad day every now and then, and with the amount of people modding HK guns as of late, it's better to have the knowledge out there so people know what to expect.

If the mandrel also had a top ridge inside the carrier key/charging handle area that prevented the upper from moving as well as the barrel, I would actually try and get my hands on one. That would be a fantastic way to do barrel work on any gun designed around this platform.

Hell, I just might make one at the shop just for ****s and giggles.
 

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Interesting approach. did the mandrel also prevent movement of the upper receiver or was it a straight rod with lugs on the end that matched the barrel extension?

Since all the force of the barrel nut is applied to the extension and to the threads on the upper, I personally, would feel better knowing that the upper was captured as well to help prevent any movement of the barrel alignment pin in the alignment pin slot.

The reason for my concern is that I have seen uppers ruined by incorrect torqueing of a barrel nut and inadequate lube (grease) which caused the upper to pivot around the barrel and caused the alignment pin to rotate through the softer aluminum and cause the barrel to be extremely out of alignment as well as damaging the upper.

Not saying that HK doesn't have their QC **** wired tight, but everybody has a bad day every now and then, and with the amount of people modding HK guns as of late, it's better to have the knowledge out there so people know what to expect.

If the mandrel also had a top ridge inside the carrier key/charging handle area that prevented the upper from moving as well as the barrel, I would actually try and get my hands on one. That would be a fantastic way to do barrel work on any gun designed around this platform.

Hell, I just might make one at the shop just for ****s and giggles.
The two large notches cut into the sides of the heavy profile are not for attaching the barrel to the receiver; they are for installing the barrel extension. When they went to the lighter profile, HK developed a different method of attaching the extension.

Thus, the mandrel that slides into the receiver from behind to secure the lugs on the barrel extension has always been the method of attaching the barrel to the receiver. This was a carry over method from the G36 (note that the tool is not the same for both platforms and are not interchangeable). The receiver itself has no support.

When slide the barrel it, there is an alignment notch at TDC. The tolerance inthe notch is very tight thus no barrel movement occurs. The torque setting is 90nm(+/- 7) which I am told is well within the outer limits. In all fairness, the barrels on the HK416/MR556 were intended only to be removed/installed by HK-trained persons using the proper HK-developed tools. So with their taught methods, it works well within the failure limits of the receiver.

However that being said, I do agree with you in that the receiver should be supported. I like the Brownell's (I think) AR15 vice block.
 

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The torque setting is 90nm(+/- 7) which I am told is well within the outer limits. In all fairness, the barrels on the HK416/MR556 were intended only to be removed/installed by HK-trained persons using the proper HK-developed tools. So with their taught methods, it works well within the failure limits of the receiver.
My HK416 Maintenance Manual (from 2009) asks for torque setting 100Nm (+/- 10Nm) and checking torque after 10,000 rounds. Is 90Nm revised requirement?
 

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This is why I need not make posts after a long day. My mistake. The 90nm is the G36. The current HK416 is 110nm (+/- 10). The current U.S. manual does not specify re-check interval for the torque, however 10K is the count for almost every other check so it probably is good practice to do so.

I would not doubt if there were slightly different specs for various countries. Is your 2009 manual a U.S. version?
 

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The two large notches cut into the sides of the heavy profile are not for attaching the barrel to the receiver; they are for installing the barrel extension. When they went to the lighter profile, HK developed a different method of attaching the extension.
Interesting. I would swear that i've seen several places where it was mentioned that the notches on the heavier profiled 416 barrels were for removal of the barrel from the receiver.

Guess I misunderstood what they were saying.

In all fairness, the barrels on the HK416/MR556 were intended only to be removed/installed by HK-trained persons using the proper HK-developed tools. So with their taught methods, it works well within the failure limits of the receiver.
Which is what I figured all along. HK isn't like some of the clone companies where it seems the guns are made in the basement by monkeys with hammers. (I.E. SW, etc.)

However that being said, I do agree with you in that the receiver should be supported. I like the Brownell's (I think) AR15 vice block.
I would like to see a receiver jig/barrel extension jig. Imagine if you will the plastic internal mandrell that comes with the receiver blocks you mention, that has a receiver extension wrench lug attached to the end.

Of course it would have to be made from steel and the dimensions would have to be much different so remove play from the system to ensure no slipping or accidental damage.

And for what it's worth, the standard AR15 receiver block that you brought up needs modification before it can be used on a 416/MR556 receiver due to the fact that the dust cover is plastic and much thicker.

I put mine in the mill and opened up the area contact area around where it contacts the dust cover to account for this (the glass filled nylon is machineable thankfully), as well as the spot where the cam pin relief bump is on the other side of the receiver. Thankfully the blocks come with a tall enough top slot to account for the higher rail in the 416 platform already though.

I also custom made a spanner wrench and then later found that an AR15 carbine stock wrench is actually the perfect size for the 416 barrel nut so long as you get one with a single tab instead of the three tab variety, but I still use my custom wrench because I heat treated it so it wouldn't bend when torqued to spec.
 

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Interesting. I would swear that i've seen several places where it was mentioned that the notches on the heavier profiled 416 barrels were for removal of the barrel from the receiver.

Guess I misunderstood what they were saying.
No, you probably did read/hear correctly as I think I have read the same. And for all accounts, it would make better sense to secure it from that location rather than the entension. However when I asked about it, that's what I was told.


I would like to see a receiver jig/barrel extension jig. Imagine if you will the plastic internal mandrell that comes with the receiver blocks you mention, that has a receiver extension wrench lug attached to the end.

Of course it would have to be made from steel and the dimensions would have to be much different so remove play from the system to ensure no slipping or accidental damage.
Exactly. When my colleague brought over his Bronell's jig, that was the first thing I thought of... machining a new insert to fully extend into the extension to help keep the barrel in place.

But I have to tell you, after removing/installing a dozen barrels with the just the support rod, I'm starting to see why the Germans do it that way... any additional support just isn't necessary.
 

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I agree that with a proper internal mandrell, the clamshells are unecessary, but i'll admit that a mandrell with an added ridge that fits in the carrier key channel would make me *feel* better as i'd rather counter as much of the force being applied to the softer aluminum as I possibly could. It'd still be a "slip on and wrench" kind of tool and be very quick and easy to work with, but it'd just have that one additional piece of support that appeals to my emotional desire to support my work pieces as much as I can.
 

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This is why I need not make posts after a long day. My mistake. The 90nm is the G36. The current HK416 is 110nm (+/- 10). The current U.S. manual does not specify re-check interval for the torque, however 10K is the count for almost every other check so it probably is good practice to do so.

I would not doubt if there were slightly different specs for various countries. Is your 2009 manual a U.S. version?
It is a draft manual in English. Do not ask how I get it, because I would need to get to US and kill you ;)

Because barrel removal and installation procedure is marked as "not aproved", I was wandering about final numbers.
 

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Discussion Starter #19
Anyone own or have access to an AH dated 14.5" upper with the lighter profile they could take a few photos of?

Thanks,
TC
 

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Considering the barrel extension is threaded to the barrel itself, then holding it from the locking lugs would be the best since that is intergal to the flange and the barrel isn't.
 
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