M2A1 Reflex Sight Project

[blobface]

So, with the rumours of those Russian grenades potentially coming to the UK, and that I'm bored, I've re-visited something I toyed with all the way back in 2011, the M2A1 reflex sight as seen on the M32 launcher:

 

 

 

I'm probably 35% there externally scaling from various pictures etc, I have decided to go for the version above as it isn't packed with rails everywhere, and I need to figure out how to replicate some of the mechanical parts, essentially make it up to work in similar ways, but it shouldn't be too hard, and I won't bother trying to wire it similar to the real thing until a later stage, but I'm now somewhat stuck, while I stripped a cheapo clone ACOG red dot sight's internal, which provides me a good 30mm working reflex sight, the reticle is way wrong, it's just a dot, but I need to recreate this. 

 

Here's what I got so far:

 

 

 

ACOG clone red dot inner tube, the reflective face is exactly 30mm, which I'll stick it into a 32mm aluminium inner tube, it's almost a perfect fit with a little machining required, but it should be okay, HOWEVER:

 

Any suggestion on how I could possibly make a replica to have the "correct" reticle? It looks something like this: 

 

Looking at all my optics that has funky reticles, they all show an LED glowing behind what looks like a super fine black film with the pattern of the reticle in negative to allow the light through, the only idea I've got is to print it on acetate and hope it works, but does anyone have more in depth experience on how I might be able to get something like this to work? 

[renegadecow]

Instead of an led behind a pin hole (typical red dots), how about making the reticle out of acrylic which the led then illuminates like a sort of fiber optic? You just position it in front of the led and it should fill in with light. It'll be pretty damn small so thinking maybe printing it might be easier.

 

edit: derp. The led has to be at the edge of the reticle for it to glow, that or you frost one side so the light is dispersed within.

[aac]

how large or small is it ?

If it's large enough, you could take a piece of clear plastic sheet, and paint it black,  

after it's been dried, you can engrave a new pattern, i have already done this.

[blobface]

Judging by one of my reflex sights that has a cross pattern, at the point of the diode, the pattern itself is 2mm across, since this is a grenade sight, it could be larger, but image size is also affected by distance between lens and diode, so it's difficult to gauge, here's a blurred image of it look down the latest version:

 

 

The black rectangle just below the reticle is where the diode sits, the block looks larger than normal reflex sights, so do the reticle even though it's blurred, so my feeling is that the size of the diode pattern can't be bigger than 3-4mm, 

 

 

Will print these on acetate and do a quick test tonight. 

[blobface]

snip

 

Do you mean having a small square of frosted acrylic acting like a fibre optic so that the light is diffused across the pattern instead of directly behind? Or you mean make the reticle in acrylic? It'd have to be super tiny.

[renegadecow]

Either or. A small 3D snowflake or a small square with the pattern being frosted so it refracts light. I imagine some of the better printers have very tight tolerances so would easily be able to print something as small as that out.

[blobface]

 

Finally got the based worked out, next is onto the locking mechanism, will avoid the reflex business until the mechanical side is sorted for now. 

[blobface]

Low quality "quick" print for the main body. 

 

 

  

 

 

Think I found the perfect switch for it!  

[Tw1tch]

Very interesting...

 

Don't suppose you'd be up for building another one to sell if it works out?

[blobface]

If / when it works out, most things are easily re-creatable as they'd be a CNC job, everything except the lens, I have to gut a China clone sight to get a reflex lens, but I have absolutely no idea how to buy them in bulk / make them myself.. which is pretty much the only thing that limits me creating more than one, but I'm still miles away anyway, the wiring and the reflex diode location / angle alone will take a lot of work. 

[aac]

If / when it works out, most things are easily re-creatable as they'd be a CNC job, everything except the lens, I have to gut a China clone sight to get a reflex lens, but I have absolutely no idea how to buy them in bulk / make them myself.. which is pretty much the only thing that limits me creating more than one, but I'm still miles away anyway, the wiring and the reflex diode location / angle alone will take a lot of work. 

This project's ar such time consumers, that they become unnafordable !

[blobface]

they become unnafordable !

 

It all depends on how I design it, but since I started this with no intention to sell, there'd be a lot of botch jobs that aren't very well thought through (again, the parts to do with the electronics and reflex reticle), which will end up being time consuming if more than one is made. I can't imagine anyone would want to buy one off me, considering I'd have to charge enough to cover potential pain and suffering involved, but will see, I'm kind of really using this project as an excuse to learn a new software properly, and hopefully add a light sensor for the adjustment which will allow me to learn Arduino (planning to use a Sparkfun Arduino mini and a 3.7v lithium aaa)