Gonna setup Hk416 10.3 upper with my Colt M16A1 lower. Have a few questions hope your guys can help, Thanks in advance

1. I already have the regular (not HK416) Geissele SSF trigger installed on the M16 lower, can I still use it with the HK 416 upper? Will I have any issues with the HK upper?
2. I plan to use the Sprinco "Blue" Spring, Vltor A5H3 buffer, with HK416 Slim Line Stock. Which tube should I use, the HK or Vltor tube? I know the Vltor A5H3 buffer is longer, so If I use HK tube, am I gonna have issues? or I use Vltor tube, will HK416 Slim Line stock fit?
3. I'd like to replace the black rail with a RAL8000 HK rail. Does HK make any RAl8000 rail for 10.3 upper?
4. Are the HK V4 and V7 grip both gonna fit my M16 lower? which one should I get?

First of all, with your setup, on behalf of everyone else - Fuck off! (That is a fuck off is motivated by extreme jealousy - nothing personal...  )

 

Having shot what you're setting up, it is awesome.  Unfortunately, when I got to "use" a 10" upper on a M16 lower, it was property of Uncle Sam and I couldn't take it home.  If you're shooting suppressed, get a carbon scraper for the piston housing since it gets really dirty and is a bear to clean otherwise.  I think Midwest Gun Works had the 416 cleaning kit that has the scraper for $60 or something like that.  A SCAR MK16/17 scraper can also work, as does one for the M249.  It saves an enormous amount of time cleaning.

Do you want to trade a kidney for your setup?  I have two and only need one.  Both have been meticulously preserved for your enjoyment with alcohol

Thanks a lot man!!!! That's some very helpful information!

I think your kidney worth a lot of more than my current setup. I will consider a trade when my two NIB M16A2s(with Property of U.S. Government marked) get out the NFA jail

I need to disagree with the reply to #1.

The Geissele SSF (non-HK) will not work with a HK upper. The BCG on the HK416 has a firing pin safety and the SSF will not have the clearance to disengage the safety.

You WILL need a mil-spec FA hammer or the HK specific trigger group from Geissele.

Check here for more info and a list of triggers that work.

Well, I hate you OP. We expect pics.

That whole thread talks about the MR223 and MR556.  The 416 upper on a M16 lower is a different animal.  The only issues that I have heard of with people using the SSF with the 416 is the occasional light primer strike, which can happen with any match trigger and hard primers (like in any milspec ammo).   The firing pin safety that needs clearance is in the MR556/MR223 and pre A1 416, and this lower has slightly different geometry than the M16.  HK made the 416 upper to function on any milspec M16 lower, and they have sold tons of upper kits for that purpose.   The whole HK specific safety is why Geissele makes a specific HK trigger, not due to other issues in a non-HK lower.  

Without a HK lower and HK416 specific trigger, you lose the ability to use the safety when the hammer isn't cocked. It just has the exact same manual of arms as any M16 standard system.

To the OP - try it out.  If it doesn't work reliably, switch to a standard M16 FCG.  No big deal.

If you look at the detailed comparison though, the MR556 and 416 uppers are not as different as you might think and the MR556 lower vs M16 lower geometry differences are not as dramatic as you are making it out to be. I think you are misinterpreting what I am trying to convey here.

I have a Spike's Tactical lower with a HK416 upper and my Geissele trigger did not work. The firing pin safety is in both 416 and MR556 BCG (I have both uppers) and you will need a FCG that has a tall hammer and that is the reason for the MR556/416 specific set up IF you wanted to stick with Geissele (otherwise a normal AR full auto trigger group works just fine). The Geissele SSA I have is not tall enough to hit the firing pin safety. I had to switch back to a standard Mil-Spec trigger group with a taller hammer and everything worked as expected. Having said that, I just noticed the OP said he has a SSF group (Mine is a SSA, A for semi auto). That might work if the FA hammer is tall enough. Try it out like interfan says. Just keep in mind if it does not work then the first place to look is the hammer.

As another note, the Geissele trigger for the 416/MR556 does NOT maintain the HK hammer down-selector on safe feature.

I don't mean to misinterpret, the thread and comparison by Montrala (a good guy by the way) is mostly on his MR223.  The MR223 is very different as a lower than the M16.  It is like the pre-A1 416 with the STANAG magwell and slightly different internal dimensions to meet the German anti-"weapons of war" business   You are right, the MR556 and 416 are very similar, with current versions being nearly identical except for all the extension/carrier/etc. crap to keep you from using it with a FA lower.



Yes, the SSA wouldn't work, nor would most SA match triggers.  Maybe the KAC one would since the hammer is taller.  The SSF should have a taller hammer that would be close to the same height as an M16 hammer.  I have seen a SSF work in the setup that the OP is using.  The guy using it seemed to like it except for the occasional light primer strikes.



The Geissele guys at SHOT Show said it did.  I haven't seen it used in person.  It is good to know it doesn't do it.

Nice setup.  Been thinking of getting a 416 upper for my M16 or RDIAS.