MFP Autos

Help with HK416 Current / Proprietary Fire Control Group

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Good Afternoon Folks,

I'm having some difficulty installing the updated HK416 fire-control group in my postie 416 lower. I've installed countless GI AR trigger groups, but have never worked with the H&K one before. It looks like they broke out the trigger from the sear / disconnector channel (they call this the "rocker") and added a "trigger bridge" to shield the disconnector. There is no longer a trigger spring, but basically a shorter disconnector type spring that tensions the rocker against the receiver floor. Does anyone have any experience with these?

I installed everything as best I could from the grainy MR556 exploded diagram on the Brownells website. I know the design is supposed to allow the weapon to go on safe with the hammer down. When the selector is on safe and the trigger is pulled, the hammer is falling. Further and most perplexing, when the selector is on semi and the gun cycles, the disconnector will not reset after releasing the trigger. When this happens, the selector must be rotated to either auto or safe to disengage the disconnector from the hammer. 

Does anyone have any idea what's is causing the trouble? Does anyone have access to a recent copy of the 416 armorers manual? I have a copy from 2007, but that was before they changed the trigger group.

Thanks,

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Sounds like you may have the wrong disconnector.  The area above the disconnecter spring (under the bridge) is not as "tall" as it is on a standard M16 disconnector.

The bridge will push down on the back of the standard disconnector and prevent it from engaging the hammer in semi-auto.  Try removing the bridge and function check without it.

That should tell the tale.

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Posted (edited)

On 1/4/2020 at 9:31 AM, shawnflyz said:

Sounds like you may have the wrong disconnector.  The area above the disconnecter spring (under the bridge) is not as "tall" as it is on a standard M16 disconnector.

The bridge will push down on the back of the standard disconnector and prevent it from engaging the hammer in semi-auto.  Try removing the bridge and function check without it.

That should tell the tale.

Thank so much for the response. It has been very difficult to find anyone who has experience with the later 416 FCG.

I took out the bridge and was still experiencing the trouble, but I took a look at the disconnector installed and though it is stamped "HK", I know for a fact that it came out of a very early 416 originally. I have a brand new 416 disconnector on hand and it is indeed cut higher above the spring.

When I installed the new 416 disconnector, it fixed the problem of the hammer being captured semi-permanently by the disconnector on semi, but now it's dropping the hammer ("firing") a second time upon releasing the trigger. The hammer is also still dropping when the selector is set on "safe" and the trigger is pulled.

I now have a brand new current production factory 416 trigger, rocker, disconnector, bridge and springs. The only thing that isn't current factory production is the hammer. It's a HK416 hammer, but out of the same early 416 the original disconnector came from. Is the current production 416 hammer any different from the original? 

Thanks again for your help.

Edited by MFP Autos

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Posted (edited)

You’re welcome. Happy to help.

Short answer is yes; the hammer is different.  

The sear surface relationship appears to be different between the old style trigger / hammer vs. the new style rocker / hammer. It sounds like your not getting proper engagement of the sear surface of the rocker w/ the old style hammer.

Even the retaining pins are a bit different because there is no J spring in the middle of the hammer to engage the center groove in the pin to retain it.  The standard pins can probably be used if you install them with the outer groove on the left side of the firearm.  

I believe the only interchangeable part is the selector. 

 

Edited by shawnflyz
added info; clarity

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Understood.

Thank you again for clarifying. I initially thought that only the obviously proprietary parts were different - turns out not to be the case at all. I'll see if Midwest or HK-parts has a proper hammer in stock; strangely it's the only 416 fire-control part Brownells doesn't seem to have in their catalog.

Thank you for all of your assistance.

 

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