Help with my 416 upper

[Ronnie77]

--I edited the title of this thread because I have a problem with my 416 upper, and did not want to start a new thread. Question is in post #5.--

I have a 416 10.5" upper inbound, and would like to know what spare parts could or should be on hand? It is used, and I was told it has a little over 500rds through it already, about half of which where shot suppressed.

I will not be shooting it in full auto, however I will be using a suppressor from time to time. And I will be using it for carbine training & competitions. I expect to put a good amount of rounds down range, but not on a daily basis.

I have other AR's (Colt, LWRC, LMT) that I use for this, and normally keep an extra bolt, buffer & spring. And if I have to travel for any training courses, I would bring a spare rifle anyway, but I would hate to switch to a different rifle unless I really had to.

I just would like to know from those of you who have experience training with this particular platform, what should I keep on hand.

[G3Kurz]

Based on your useage you likely will only needs parts that are lost or broken by the operator. I would include a firing pin spring, rail system locking screw and anything else you might like to have handy should it be lost (sight parts, etc.). At a minimum you should have trouble free use of the upper in your scenario for at least 20K rounds. If you are very paranoid, invest in a complete bolt head and few gas piston rings though likely you'll never use it/them.
G3Kurz

[RyanH&K21EOwner]

Based on your useage you likely will only needs parts that are lost or broken by the operator. I would include a firing pin spring, rail system locking screw and anything else you might like to have handy should it be lost (sight parts, etc.). At a minimum you should have trouble free use of the upper in your scenario for at least 20K rounds. If you are very paranoid, invest in a complete bolt head and few gas piston rings though likely you'll never use it/them.
G3Kurz

I concur with Jim on this...

I'm overly aggressive about protecting my tools so I go the paranoid route just in case...

You can never go wrong with having a few HK 416 spare parts and AR tools close by...

A nice AR take down tool kit set will go a long way with extra spare parts on hand...

[Ronnie77]

Kurz & Ryan,

Thanks for the responses.

I picked up a few things from Adam already.
And I just might get a complete bolt head as well. Just in case..
Like you said, you can't go wrong with having a few extra parts around.

[Ronnie77]

Ok, I need some help here.

I just got my 416 upper, I pinned onto my RRA lower and for some reason I cannot pull the bolt back at all.
I mean it will not go back even a little bit, like it is locked on something.
I open it up and it pulls back very easily, but when I close it I cannot move the bolt.

My lower has a RR 2-stage trigger, with a SOPMOD stock & Milspec tube.

Is there something that I am missing?

[Big Bore]

This very common with some lowers when used with the NM 2 -stage trigger. I only use WOA tuned RR NM 2-stage triggers in my builds and in all three of my LR-308 lowers and one Olympic lower, the bolt carrier hits the top of the hammer and prevents it from being pulled back. However, on all of mine I can pull the carrier back about 1/4 to 1/2 inch before it locks up so before doing what I am going to tell you to do make damned sure that is what is happening on your 416 also. See note below***
I called RR about the problem and they said to take a trigger stone or other fine stone and remove about .003 to .005 inch from the highest part of the hammer in relation to the top of the lower as you would see the hammer in the cocked position. Take your upper off and cock the hammer. While the lower below is an LR-308, the procedure is the same for any AR lower.
See how the very tip of the hammer extends up from the lower in the cocked position?


Measure this height from the top of the lower to the highest point on the hammer:


Then take a stone and run it parallel with the top of the lower and stone off about .003 inch off the highest point on the hammer and try again.


You only want to remove enough to let the carrier operate freely but on one I did have remove a lot more than .005 inch. I had take it down about .015 inch on the Olympic lower to make it free the carrier up. This is not a problem since it is not the tip of the hammer that hits the firing pin; that occurs much lower on the hammer. But if you remove too much then the carrier will not push the hammer down far enough to catch the sear or disconnect. And once done it does not mean that if you put the trigger on another upper that it will work on it also, but so far I have not encountered any problems but I have also not put another upper on the Olympic, the one that needed more than .005 inch removed.
Just make sure that this is the problem before you start stoning any metal off the top of the hammer. It cannot be put back on.
To test, assemble the upper to the lower and gently try to pull back on the CH. The bolt carrier usually moves a little before locking up (it compresses the hammer fully and bottoms out, forcing it will damage the trigger so don't do it!).
Use the FA to push the BC forward again and push out the rear take-down pin. Holding the upper firmly against the lower, pull back on the CH and you should feel the carrier contacting the hammer and push it upwards a little bit.
If you pulled the carrier back too far in the past and locked it up and had to cuss and pry to return it forward, you pretty much have your culprit, it got locked against the top of the hammer.

***Now, the fact that you said your BC does not move at all has me concerned. That sounds like the back of the carrier is hitting the buffer tube and there is misalignment there. Check that to make sure before you take the stone to anything. If that is the problem I have no suggestions for a cure.

[Ronnie77]

Big Bore........ You are the Man!

What you explained is exactly what I am experiencing.
I should have been more clear in my earlier post, so I apologize.
When I pull on the CH, it does come back just a tiny bit before it locks up.
I would say maybe a 1/4". I will check it again tonight just to be sure though.

After examining it last night, I came to the conclusion that it was a problem with the hammer, but I could not understand why or what to do.
So I figured I would ask the pros.


I thank you a great deal.
And where can I get one of those trigger stones?

[G3Kurz]

OUTSTANDING REPONSE Big Bore! You rise to the cream of the HKPro crop with that post! Quality in all regards.
Well done!
G3Kurz

[Big Bore]

Awe, shucks, it twernt nuthin. Nice to be appreciated though. ;)
Brownell's sells them but any fine cut hard knife sharpening stone will do. Just make sure you don't use a coarse or medium stone. One of those black, hard finishing knife stones or a hard Arkansas stone will work just as well. Just don't use much pressure and take four or five strokes and re-measure. Take off a couple thousandths and reassemble and try again. On the Olympic I resorted to a pillar file (makes a cut so fine you almost don't need to polish it) and then finished with a trigger stone. .015 was a lot of metal to remove and I was getting nowhere quick using just the trigger stone.

[Va_Dinger]

Big Bore is well known as one of the most respected HK experts on the net.

He has helped me out several times.

In my opinion HKPro should immediately hand him mod/staff powers.