Simple enough question for which I have no idea. But, heres really my (fixed) problem.

I run a MUM (Mini-14) monocle. (In retrospect should have went PVS14) I wanted to get an adapter to allow the use of the PVS14 mount, so bought the following:

J Arm adapter for Sparc

Well lo and behold, it didnt fit on the MUM mount. I managed to fix it up easily enough with a small file and just filing the inside of the mount but it seemed damned odd it didnt fit. What I'm not clear on is whether the adapter was fine and would work on a Armasight Sparc mount, or whether the adapter is cut rate cheap shit and out of spec?

As i said I managed to get it to fit so this is more for my own curiosity. It seems damned odd Armasight would produce a unit not following milspec standards for attachments and rails and such but maybe the rail on the Sparc isnt a picatinny rail so there is no "spec" for it.

How much filing did it take? I have one of those adapters and it wouldn’t fit on mine either.

Honestly? Quite a bit more than I expected! One of my other hobbies is RPG games, so I have a nice hobby file set. The triangular file is a perfect fit for filing it out and opening it up so it fits. Heres one example.

Hobby file set

No.

It is not a Milspec mount.

At least, as far as I have been able to determine, there is no milspec for the mount.

Regards
David

I’ve had two Sparcs and those adapters worked on both with no filing... and I bought two adapters.

Can you test the adapter on a MUM? In my case I'm not using it on a Sparc. I suspect the Sparc has a off sized mount hence the adapter fits the Sparc but the adapter will not fit other units.

Having used many MUMs and MUM clones, I have to say that each non-MUM housing has different sized rails, and the same applies for non-MUM accessories - they seem to be whatever sized and either fit or don't fit, or have a bad wobble or a little less bad wobble. Unfortunately there is not much original MUM accessories available, all are 3rd party. The MUM J-arm on the other hand seems one of the best plastic arms there is. I have a differing opinion on going PVS-14 instead of a MUM, they both have their pros & cons, but I personally like a MUM due to it's weight and easier to adjust optics. Also slightly better image quality in some aspects. Only issue is the mounting one, but today there is a good selection of bridges and even a dovetail arm which is okay, though not optimal.

So I don't know the answer to your specific question, but sure that a Spark accessory can be sized to whatever "specs"

Edit: and speaking of Armasight rail specs, just read on the Breach rail sizing & placement oddities. If they went with the MUM "spec" they would've put the display 90deg rotated from what it is now, but as it is, they placed 2 new rails on top & bottom of the unit and you need to use those to get the view in proper orientation. And that means no pre-existing bridge & arm will place it correctly on your eye unless it has enough IPD adjustment to offset the misplaced rail. Also reading people say the rails are the wrong size even compared to other Armasight products.

They use many different manufacturers to make the housings & optics, and it seems every manufacturer has their own rail spec instead of Armasight providing a spec that they would all conform to. Would be too easy!

I’d need a Mum

Armasight's crap mounts only fit their stuff unless you modify in a fashion like you did.  SPARK owner here and I still think Armasight's mounts are crap.  You can make them work but they are quite pricey for what they are and typically don't work for many people they want them to.

Armasight's aiming adapter for the SPARK fits the MUM just fine. ( or rather, the MUM fits it. )

David

@2JokersWild after filing, you used a standard JArm? Can you take some pics? I did some filing last night and got the adapter to fit, only to realize I either sold or lost my last standard JArm so I can’t test the adapter to JArm interface. I’m trying to decide if I want to grab another standard JArm or maybe one of those Dual Dovetails/Wilcox Dovetail JArms/RQE shoes and a new mount.

Thanks.

I dont have a "standard" J-arm (I dont think!), in the sense that my J arm is for a MUM rather than a PVS14. I think the standard J arm uses a screw whereas my J arm uses a spring loaded latch. I only bought the adapter in the event I end up with a screw type J Arm. Heres a few pics. You can see on my J Arm where the groove has a indent which locks in place on the monocle.

You can see the shiny bit in the mount where I had to file it down, the triangle shaped file fit pretty well perfectly. Once filed it fits on the monocle.

Yeah, we are in the same boat.


Time to buy a J Arm from someone!