Just got my Helios QD today (fricken amazing can!).  For now it's directly mounted to the rifle using the direct thread, but am considering a QD mount.  Anyone know if the Keymount muzzle brake and KeyMo work?  It appears there are 2 different versions of the KeyMo - which would it be, if it fits (sico omega / saker)?

The Helios QD comes with an adapter to use Omega compatible mounts, the Omega version of the Keymo should work fine with that.

I've read that they changed their design, on Reddit NFA.  Unfortuantely it doesn't look like it will work now?  In any case, the YHM Kurz appears to be the best solution for me....but that appears to be out of stock.

There are at least three different versions of the KeyMo. All Omega pattern 1.375x24 KeyMo mounts will work with the Helios QD with all KeyMo muzzle devices I've seen when using the QD Adapter Ring which is included in the Helios QD Kit.



Dead Air released a new KeyMo design maybe four months ago, the version with no extra material in front of the threads (which I'll call Gen 2 KM), which replaced the old KeyMo design, the version with .275" of extra material in front of the threads (which I'll call Gen 1 KM).

The Gen 2 KM paired with the KeyMicro brake allowed you to use that specific combination of parts on the Helios QD without using the QD Adapter Ring that's included in the Helios QD kit. Soon after releasing Gen 2 KM, Dead Air then changed the design of the KeyMo mount again after there were issues reported here and elsewhere of KeyMo mounts not fitting various silencers due to male thread issues on the KeyMo mounts. We know it's not an issue with the CGS side of the equation since all of our parts are checked with thread gauges, and because they were rechecked when we took the parts back to see what the issue was. Fitment issues were also occuring with other manufacturers silencers. The newest KeyMo mount (which I'll call Gen 3 KM) had ~.05" of material added back in front of the threads, and that extra material prevents the KeyMo from shouldering in the Helios QD because that extra material bottoms out on the internal taper shoulder of the Helios QD.

What I wrote about on r/NFA was in response to peoples concerns about KeyMo fitment issues due to the different versions of KeyMo that were being released. As an example, people that had thread fitment inssues with the Gen 2 KM (which fit) sent their Gen 2 KM back to Dead Air to be replaced/fixed, but they were then sent the Gen 3 KM (which didn't fit) as a replacement for the Gen 2 KM because the Gen 2 KM was no longer being made at that time, so when they tried to assemble the Gen 3 KM and saw it didn't shoulder up in the Helios QD they were confused.

Here are some pictures of the different KeyMo generations:

Gen 1 KM (does not fit without using QD Adapter Ring)
Gen 2 KM (fits without using QD Adapter Ring)
Gen 3 KM (does not fit without using QD Adapter Ring)

Regardless of all that, the easiest thing to remember is that all KeyMos from Gen 1 through Gen 3 regardless of KeyMo muzzle device choice (and all other 1.375x24 Omega pattern QD mounts) fit the Helios QD no problem when you use the QD Adapter Ring. There were just a few random combinations people noticed that happened to work without using the QD Adapter Ring.

See here for how the assembly looks with the QD Adapter Ring:

Link 1
Link 2

Wow thanks for the very detailed response!