mounting Holosun HS403c on AR with M-Lok rail

[old lady new shooter]

I AM NOT MECHANICAL.

I bought a Holosun HS403c red dot for my new AR, but I didn't realize it's not made for an M-Lok rail. The instructions say "Picatinny or Weaver rail. Industry standard mount allows for attachment of after market mounts." (What does the second sentence even mean?)

I saw a thing that appears (CAN YOU PLEASE VERIFY? IS THIS WHAT I NEED?) to fit on an M-Lok to provide a picatinny interface, https://bravocompanyusa.com/bcm-3-inch-picatinny-rail-section-aluminum-m-lok-compatible/ (aluminum) or https://bravocompanyusa.com/bcm-3-inch-picatinny-rail-section-nylon-black-m-lok-compatible/ (nylon), the nylon one is much cheaper but includes the following on its page, in red no less:
Please note: Nylon/Polymer Picatinny rail sections are for NON-load bearing accessories only (grips, hand stops, light mounts). For load bearing accessories (bipod mounts, sling mounts, vertical grips, barricade supports), we recommend aluminum Picatinny rail sections. Do NOT exceed 20 in/lbs. when securing fasteners on Polymer accessories. Aluminum Picatinny rail sections may be torqued to 30 in/lbs.
If this is what I need, I guess the aluminum is better... ?

If the above is not what I need, what do I have to get / do ?

 

[LoonWulf]

Are you trying to mount it on your rail, or on the receiver? 90* or .45*s?...im assuming you have an Mlok, freefloat handguard?
If your trying to attach it to your receiver you should be able to bolt it straight to the flat top (assuming you dont have a true carry handle receiver), and if you want it on top of the hand guard, it should bolt on there as well.

What you linked will work for adding a short section of Pic rail to an M-lok forend. You can then attach you Holosun to that.

 

[old lady new shooter]

Thanks very much for answering.

Meanwhile another friend told me the rail on the upper receiver is Picatinny, M-Lok is on the handguard (yes, free-float). So I can mount the red dot on the receiver and worry about the M-Lok later when I go to attach the sling hardware (which I don't yet have). This is my first gun that's not a revolver, so all this is new to me, and the spec only mentioned M-Lok.

 

[LoonWulf]

Glad you got the info you needed.

 

[CapnMac]

Yep, stick the thing on the forward most point on the receiver (tight enough not to wobble, but not cranked down). Now, get behind the thing and see if that's too far forward or not enough. In the latter case, you need an MLOK to Pic conversion rail. If the former case, move it back half a base length (like three slots on the pic rail), and test again.

Goal is that you can keep both eyes open and have a dot in your vision. So, you need the tube far enough back that it really is hardly noticeable but does not lock you in to mono-ocular vision. IIRC this is a Saint, so you are likely to be more forward on it than on an M4 or A2/3, which is why I'd start all the way forward on the pic rail.

I'd go around the house looking at what you are likely to have for a backstop. I'd check this curtains closed and curtains open. Once you have a good comfortable spot picked out, then you can tighten down the sight.

On my A2 with carry handle, mine wound up one notch from the front of the carry handle mount, which looks goofy installed, but is really comfortable to use. On the M4gery, that one is about half way back. YMMV

 

[Skylerbone]

Over the magwell is where I was told to start and that’s been that ever since.

 

[LoonWulf]

Over the magwell is where I was told to start and that’s been that ever since.

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With a tube sight thats where i like them too, with a reflex i prefer them a little farther back so the sight hood blurs out a bit.

 

[old lady new shooter]

Thanks everybody for the additional advice.