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Posted: 10/10/2016 5:03:36 AM EDT
Hi all.

I wonder if a full auto HK416 lower would be compatible with a standard AR-15 upper? Of course the full auto mode would
not work, but sometimes it would be nice just to test other uppers/calibres with a lower/trigger that I like.

Did my best with Google-Fu, but no positive confirmation about compability.

Anybody who KNOWS for a fact?

Best regards,
Kai

PS: Really keen to test 300BLK and 6.5 Grendel.
Link Posted: 10/10/2016 9:13:15 AM EDT
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.
Link Posted: 10/10/2016 9:45:15 AM EDT
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Originally Posted By RLunyATL:
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.
View Quote


The upper would of course have a semi auto bolt carrier. The full auto one in piston HK416 would not work in a DI gun.

/K

Link Posted: 10/10/2016 12:37:18 PM EDT
Here in the United States the vast majority of AR uppers these days have full auto bolt carriers. Mil HK-416 uppers run just fine on standard M-16 lowers and while I've never tried the reverse (416 lowers have no advantages over a -16 lower) it should work as well.
Link Posted: 10/11/2016 4:36:34 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RLunyATL:
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.
View Quote


You also need a FA bolt carrier AND an upper receiver with a cut out for the sear.
Semi auto upper receivers are not common but they are out there..
Link Posted: 10/11/2016 5:18:12 PM EDT
[Last Edit: 10/11/2016 5:19:48 PM EDT by Storm_Tracker]
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Originally Posted By Frens:


You also need a FA bolt carrier AND an upper receiver with a cut out for the sear.
Semi auto upper receivers are not common but they are out there..
View Quote View All Quotes
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Originally Posted By Frens:
Originally Posted By RLunyATL:
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.


You also need a FA bolt carrier AND an upper receiver with a cut out for the sear.
Semi auto upper receivers are not common but they are out there..
Are you speaking exclusively about the HK product? There is nothing to differentiate an AR15 - M16 upper receiver from semi auto to full auto, and I can't imagine anything different with HK either. Only the BCG would be different in either weapon. If I am incorrect please correct me, which would only reference the HK as I know for a fact with the ar -M16 platform does not.
Link Posted: 10/11/2016 11:24:25 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Storm_Tracker:
Are you speaking exclusively about the HK product? There is nothing to differentiate an AR15 - M16 upper receiver from semi auto to full auto, and I can't imagine anything different with HK either. Only the BCG would be different in either weapon. If I am incorrect please correct me, which would only reference the HK as I know for a fact with the ar -M16 platform does not.
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Storm_Tracker:
Originally Posted By Frens:
Originally Posted By RLunyATL:
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.


You also need a FA bolt carrier AND an upper receiver with a cut out for the sear.
Semi auto upper receivers are not common but they are out there..


Are you speaking exclusively about the HK product? There is nothing to differentiate an AR15 - M16 upper receiver from semi auto to full auto, and I can't imagine anything different with HK either. Only the BCG would be different in either weapon. If I am incorrect please correct me, which would only reference the HK as I know for a fact with the ar -M16 platform does not.



Actually there is a difference... in standard FA AR uppers, there is a sear relief cut just forward of the rear takedown lug (the oval cutout). While it is exceedingly rare to see an AR upper without it, they do exist. Now when discussing 416 and MR556 uppers, it tends to be more talked about BC it is absent on all the MR556 factory uppers I've seen. The relief cut just gives the sear on an M16 lower some room to move. In a semi AR the relief cut is completely unnecessary, but remains as an artifact.
Link Posted: 10/12/2016 12:56:08 AM EDT
So essentially, the HK416 lower fits a standard civilian AR upper regarding pins etc? And IF the BC is of the full auto version, then in many cases the full auto would work also?
That means that experimenting with a standard upper with different calibres would be possible with HK416 lower :D

/Kai
Link Posted: 10/12/2016 2:34:37 AM EDT
Yup the 416 is just like any other AR lower.
The MR223 is the one that wont work with standard upper receivers due to the different location of take down pins hole
Link Posted: 10/12/2016 5:40:02 AM EDT
Link Posted: 10/12/2016 11:05:21 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By M4-Pilot:



Actually there is a difference... in standard FA AR uppers, there is a sear relief cut just forward of the rear takedown lug (the oval cutout). While it is exceedingly rare to see an AR upper without it, they do exist. Now when discussing 416 and MR556 uppers, it tends to be more talked about BC it is absent on all the MR556 factory uppers I've seen. The relief cut just gives the sear on an M16 lower some room to move. In a semi AR the relief cut is completely unnecessary, but remains as an artifact.
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By M4-Pilot:
Originally Posted By Storm_Tracker:
Originally Posted By Frens:
Originally Posted By RLunyATL:
I'm unsure of compatibility, but why would swapping uppers eliminate the full-auto capability of the lower?? If the lower has an auto sear and 3rd pin, it will run full-auto regardless of the upper that is attached to it. That is unless I'm completely missing something.


You also need a FA bolt carrier AND an upper receiver with a cut out for the sear.
Semi auto upper receivers are not common but they are out there..


Are you speaking exclusively about the HK product? There is nothing to differentiate an AR15 - M16 upper receiver from semi auto to full auto, and I can't imagine anything different with HK either. Only the BCG would be different in either weapon. If I am incorrect please correct me, which would only reference the HK as I know for a fact with the ar -M16 platform does not.



Actually there is a difference... in standard FA AR uppers, there is a sear relief cut just forward of the rear takedown lug (the oval cutout). While it is exceedingly rare to see an AR upper without it, they do exist. Now when discussing 416 and MR556 uppers, it tends to be more talked about BC it is absent on all the MR556 factory uppers I've seen. The relief cut just gives the sear on an M16 lower some room to move. In a semi AR the relief cut is completely unnecessary, but remains as an artifact.
Huh, learn something new everyday. In nearly 30 years of building ARs I have never seen or heard of such a thing. Im assuming the cutout is the norm in most all uppers you buy?
Link Posted: 10/13/2016 7:18:07 AM EDT
Yeah, the cut out is by far the norm these days. I think the lack of the relief cut was more common by the smaller manufacturers back in the 90s? As far as more recent stuff, there are a handful, I'm not sure but I heard that maybe some of Mag Tactical's uppers didn't have it back before they folded and maybe some Anderson's? I haven't seen those for sure though.
Link Posted: 10/14/2016 1:41:52 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By M4-Pilot:
Yeah, the cut out is by far the norm these days. I think the lack of the relief cut was more common by the smaller manufacturers back in the 90s?
View Quote

The only maker who ever routinely left the sear relief off their uppers was Colt, for the SP1/Sporter II rifles and some other semi models.
Link Posted: 10/14/2016 2:30:51 AM EDT
Link Posted: 10/14/2016 4:13:06 AM EDT
I think also norinco
Link Posted: 10/24/2016 6:59:43 AM EDT
Originally Posted By KaiR:
Hi all.

I wonder if a full auto HK416 lower would be compatible with a standard AR-15 upper? Of course the full auto mode would
not work, but sometimes it would be nice just to test other uppers/calibres with a lower/trigger that I like.

Did my best with Google-Fu, but no positive confirmation about compability.

Anybody who KNOWS for a fact?

Best regards,
Kai

PS: Really keen to test 300BLK and 6.5 Grendel.
View Quote


For a fact...HK416 lower works perfectly in semi and full auto with standard AR15 uppers (DI).

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