New HK 416 22lr pistol with DIY Sig Brace

[ilikegunspdx]

I wanted to post this in case anyone else is interested in how to put a folding brace on this pistol. Cddn recently had these pistols for $349 but it comes with no brace. I was trying to figure out how to put a folding brace on it and finally realized all you have to do is put a small piece of metal (not polymer) 1913 picatinny rail on the back and then you can attach a folding brace adapter to the rail.

In this case the brace is a Sig brace but a person could buy a UTG adapter which are about $13ish on ebay and then attach any buffer tube and legal pistol brace to the adapter. Other folding adapters are available also under various names such as Ace, etc.

To attach the pic rail to the pistol you have to drill a hole in the pic rail and replace the original screw on the back with a longer screw. You can buy the small picatinny rails on Amazon for around $10 but I just took off the bottom rail of this $13 pistol laser and it works great.

laser https://www.amazon.com/gp/product/B01NC3IQM8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I'm very impressed with the high build quality of the mostly metal HK but I'll wait to comment on it in detail until I put it through it's paces on the range. Thanks!

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[hg98]

Would you be kind enough to add a few more close ups of HOW you attached the picatinny rail to the gun and then ...
HOW YOU added the folding adapter?
Thank you

 

[Ura-Ki]

Neat "Fix"

 

[ilikegunspdx]

I don't have pics handy but can try to explain. Small piece of metal (not plastic as it can deform too much) picrail is attached to back of existing metal endcap of 416. Drill two holes through pic rail and endcap at yellow arrows (you need two holes to prevent brace from rotating). After drilling you can attach picrail in any of the following ways:
1. (best) tap the holes you drilled to make threads in existing endcap. Use bolts with blue loctite to bolt picrail onto endcap.
2. (good) Use 2 bolts with nylon locknuts to bolt pic rail onto endcap. Nuts go on underside of metal endcap (I can't remember if endcap is hollow or not so check where the nuts would go to determine bolt length).
3. (quick and dirty sort of hobo, not recommended for long term but fine for a test or short term) Use sheet metal screws or similar to screw into untapped holes. This won't last long term so not recommended but fine for testing if you like it or not. U can fill holes in steel butt plate later with bondo if you decide you don't want a sig brace.

Note that Pic rail pieces often come with countersunk holes for screws/bolts so if your little pic rail piece already has holes there is no need to drill holes in the picrail.

Folding adapters etc are available in many different types and costs. The folding adapter simply clamps onto the pic rail usually with one screw the same way you would attach a light, red dot etc.

(1) best imo. Buy a folding adapter with buffer tube and sig brace already attached used from someone who has taken off a stock brace to replace it with something else. usually this is a very inexpensive route to go.
(2) Buy folding adapter, tube, and brace separately
a. Adapters are available from sig saur ($125), sb tactical $75 I think, ACE $75 I think, and a ton of others. All you need is an adapter that will clamp onto a standard pic rail and will accept a standard buffer tube on the other end. I think the evo scorpion braces use pic rail I think but don't quote me on that. There are tons of pic rail folding adapters out there u just need to search.
b. Buffer tube. U don't need anything fancy here the cheapest UTG tube or whatever is fine. Just make sure to get mil-spec size if that is what the adapter and sig brace take. Don't get commercial size unless u want all parts to accept that size. Make sure all parts are for the same size tube (i recommend mil-spec size).
c. Sig brace. Your choice as there tons of them out there. Currently my 2 favs are tailhook mod1 at $95 and sb tactical mini at $63. They are pretty minimalist. Tailhook is aluminim so could potentially scratch while sb mini is rubber.

P.S. The original post was an old post and talked about using 1 bolt (replaceing the existing). That will work fine and is probably easier than drilling 2 new holes. But you have to add a second bolt to keep the picrail and brace from rotating. Second bolt doesn't have to be substantial. It's just there to prevent rotation not to hold the brace on so it can be almost anything. I get confused cuz I've done this to 4 different guns all with different types of endcaps or receiver extensions but it's all the same basic method.

P.P.S. I forgot about the UTG adapter cuz I moved that to another gun. THe UTG adapter is a fine inexpensive adapter if you don't mind some slop compared to the higher end ones. However the UTG adapter needs modification as it is made to go onto a standard AR reciever (which this gun is not). So basically you have to cut off the front part of the adapter -so that it is a flat surface that will mate to the flat surface of the existing endcap- and drill two holes into it. Probably not worth messing with unless you want to go really cheap and/or like to fiddle with making things fit/work.

P.P.P.S. If you want an attachment spot for a QD sling on the back, you can add a standard AR end plate that has a QD mount. The end plate goes between the receiver and the existing endcap. I put one of those on mine and it works perfect. However I kind of don't like a sling on it so I never really use a sling.

Here is the same brace mounted on a Stribog. You can see one screw mounts it to the pic rail on the back of the Stribog. So as long as you can get a piece of picrail on the back of a gun you can attach one of these folding adapters to it. picrail is hidden under the folding adapter in pic below.

 

[hg98]

Mate, you are a bloody LEGEND !!!
Thank you for taking the time to post this.
It's members like you that selflessly make contributions that make it easy for the rest of us that are following in your footsteps.
Have a blessed day.

 

[Member 34319]

KNS precision makes this.