From what I understand if you have to modify the weapon for it to fit, then you cant install it..? Just like the fact that you can make an HK sear work in a USC or SL8, but you have to extensively modify the lowers, so you cant legally do it.
I don't have a DIAS so I really haven't done any research on them, just what I see discussed around on the ever-reliable internet legal reference service... lol

 

Where have you seen this discussed? This is a question I have as well.

Can you put a 416 upper on a MR556 lower (with FA parts) and use a RDIAS? Will it work with the MR556 upper?

 

It is an AR type weapon so there would be no leagal issue.

 

Saying there will be no legal issue because it is an "AR type weapon" is like saying an MKE gun is an "HK type weapon" so there would be no problem putting an HK sear in it. It makes sense, but making sense doesn't make it legal.
A Umarex 416 .22 or a Colt M4 22LR is an AR type weapon, doesn't make it legal for a DIAS. A GSG5 is an MP5 type weapon, but no go on a HK sear.
I'm not saying you can't do it, it would make sense and I hope you can. But I would make sure you get some info direct from ATF or someone who has some first hand knowledge of this before you do it.
Is the MR556 compatible with a standard AR15 LPK? I'm not sure but if I remember right it is different, which means you would have to modify it, which means no DIAS? Not sure.

 

I haven't had hands on with the 556 yet but I was under the impression that HK modified the upper/lower so as to not be compatable with mil-spec uppers/lowers. It seems to me that they may have moved the rear take down pin location to effect this modification. Cutting the slot for the sear shoudn't be an issue but wether or not it would work with the new pin location is a different story. But since we suck and HK hates us it would surprise me more if it could work than not.

 

The lower takedown pin is in the standard location. It was moved to on the MR223, which is the European version, as to comply with some of their BS gun laws.

 

I have not had my hands on a MR223 yet but from the pics i have seen it should work. I have a rdias and thought it would be cool to have a HK for it. In theory all you would need is full auto hammer,trigger, disconector,selector and bolt carrier. I recently went to a 40hr AR15 armorer school and now have a better understanding of Stoner's DI system.

The DI system is quite genius. The recoil impulse is in direct line with the bore. As most of you know on a DI gun the gas travels through the gas tube, THROUGH the gas "key" on the bolt carrier and forces the bolt STRAIGHT to the rear (in line with the bore). A 416/MR223 or any piston gun is going to force the bolt back and down causung the front of the barrel to rise.

Durring the armorer class we learned many of the reasons the AR/M4/M16 platform has made a name for its self as being unreliable. The instructor used to work for Colt and explained in detail how Colt and FN built their guns to the TDP(technical data package) He showed several comparisons of inferrior parts made by Bushmaster,Stag, Oly etc.

It made me think about the MP5 platform. Every one agrees the MP5 is one of the best subguns ever made but if Special Weapons made 10x as many MP5 as HK we would say the MP5 is an unreliable platform.

Like I said before i have not even handled a HK 223 but was seriuosly considering one as a rdias host until I learned more about the DI system. Just my .02

 

The recoil impulse is in direct line with the bore. As most of you know on a DI gun the gas travels through the gas tube, THROUGH the gas "key" on the bolt carrier and forces the bolt STRAIGHT to the rear (in line with the bore). A 416/MR223 or any piston gun is going to force the bolt back and down causung the front of the barrel to rise.

Please explain what you mean by "down" Any AR derived platform utilizes the carrier assembly being in line with the bore, whether piston or DI, there is no "down" component, just rearward travel.

 

I don't think anyone has adapted the MR556 lower to accept an RDIAS yet and posted pictures, but users on this board and elsewhere have put RDIASes into other lowers to work with HK 416 uppers.

 

Gotcha. I was under the impression the same held true for the US guns as well. In that case...nifty!

 

Any good pics of the bolt carrier out there? I know that full auto bolt carriers are no longer considered a "machine gun" part. My Adams Arms piston upper has a full auto compatable bolt carrier that came in it stock!
So I guess the options are:
-stock Mr556 bolt carrier, if it currently "full Auto" compatable
-416 bolt carrier if it fits
- modify a MR556 bolt carrier (this would suck)

let me know your thoughts guys, I have yet to get my hands on an MR556 to check this out

thanks,
M

 

Actually he is correct, that is why piston guns have the "ski's" on the carrier and you see "carrier tilt" wear on the buffer tube.
Had a little show on my LMT piston gun, and even HK ran into issues during development of the HK416 and corrected it.

The point of contact is on the top of the bolt carrier key with the piston rod, not straight back as with a DI system since the gas is "guided" through the key and onto the bolt itself.

 

The RDIAS *is* the registered NFA part, so putting it in AR pattern weapons is legal, no matter what AR pattern you put it in. The MR556 operates exactly the same functionally as the original AR15 design, aside from the piston. A normal AR15 that has a sear block (old colt lowers) have had the sear block removed and the RDIAS installed without issue.

 

Again, the HK sear *is* the registered NFA part, but that doesn't mean you can put it whatever 'HK pattern gun' that you want. Just ask MKE, Umarex, etc. Same goes for a DIAS.
Advising caution is one thing, but be careful giving approval for NFA stuff unless you are a lawyer or ready to pay for someone's defense because you told them it was ok... lol

Also, again, I'm not saying you cant do it and I might be waaay off. The only reason I even replied is that I thought I read that it uses a completely different LPK so it might need a little research first.
I think with the price we have to pay for a sear or DIAS you should be able to put it in anything that you can make it work in. Just use caution thats all.

 

Houston we have a problem. After some Googlefu it looks like there may be a problem. It looks like HK put a tab in the upper that coresponds with a notch in the carrier of the semi MR223. You would need to notch the 416 carrier or remove the tab from the upper. Not sure if ATF would go for that (think UZI semi blocking bar and MKE bolt tabs)

One way to get around the issue is to aquire a real 416 upper ($3000) and put it on a MR223 lower.

 

another pic looks like tab is part of the barrel extension

 

better pic of carrier

 

I'd remove the barrel and grind off the tab or swap the carrier for a f/a one or weld up end of the carrier to extend the sear trip that last little bit.

 

Welding would f this thing up, bet a "dovetail" type slot could be wire EDM'ed and a piece force fit into place to "fix" it......

 

As noted already, the MR556 has the barrel extension that's key's into the bolt carrier. Also, the MR556 carrier is a semi-auto carrier...so either way, you're gonna need a f/a 416 carrier while also removing that barrel extension tab, OR get a 416 upper to run one of these things with a RDIAS.

eta. an RDIAS should be perfectly legal to run in an MR556 lower...and the the MR556 lower will accept any other standard AR15 fire control group.

 

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