After many months, some progress Spurred on by visiting RS Props' birthday party a few weeks ago, I decided I had better make some more progress with this, even if it means making an 'interpretation' as there doesn't seem to be any more reference likely to be coming in the near future.
In my last update i'd made the muzzle end of the holster by modifying the castings of the Safariland 1090 that Rob at RS had made for me. The next step was to start working towards the front of the holster, i.e. the main inner and outer side plates. How these side plates connect to the muzzle end is one of the few areas we have a decent reference photo of, from the Wired article:
From the thickness of the 1090 part, I came up with about 6mm for the thickness of the outer plate. There is a large clamping screw in the centre of the plate (and the centre of the trimmed-off circular end of the 1090 part) and a smaller locating screw that is just there to stop the plate rotating around the clamping screw.
The inner plate is attached using a sandwich-type construction. The plate itself is the same width as the Safariland part (approx. 2mm) and has a butt joint onto it. The actual attachment is provided by thinner (approx. 1mm) clamping plates that are attached either side of the butt joint, with a felt pad stuck onto the inner plate to prevent damage to the blaster.
As all the available reference shows the holster with the outer plate facing the camera (though there is a section in the middle that can only partly be seen on my fuzzy screencaps), I decided to start with that. At the rear it has a curved arm that goes up the side of the receiver to the hammer area, where there is a button head hex bolt that screws into a threaded spacer that connects the outer and inner plates together. I therefore needed a material that was easy to form, so I bought a sheet of 5mm ABS.
I sketched a design for the outer plate on paper and then stuck it onto a sheet of thick cardboard and cut it out to see if it looked right. Once I was happy with it I transferred the outline and measurements onto the ABS sheet, cut it out and filed it to the basic shape. I then got out the heat gun and formed the curve by rolling it around a glass jar. For the return at the top of the curved part where the hex bolt goes, I initially tried filing a V into it and using heat to bent it upright, but wasn't happy with it so I cut it off, filed both surfaces flat and used EMA Plastic Weld to weld it onto the main part in the correct position.
To connect it to the muzzle part I decided to use a countersunk M4 Hex screw as the clamping bolt. I was going to use a thin nut in the existing slot on the inside of the 1090 part but found some M4 weld-in 'tee' nuts that with a bit of filing fitted into the slot and would spread the load a lot better than a nut:
That was the the outer plate more or less done, The inner plate would require a bit more thought and imagination (as there's no pictures of anything other than the muzzle end of it), so while I was thinking about that I decided to work on the front eye for the shoulder strap that is mounted on the spacer that connects the two plates together. I'd decided to use an M4 button head Hex bolt on the outer plate and from the single picture where it can be seen, the spacer itself doesn't look much thicker than 4mm. Without access to a lathe to make mu own, I found some M4 sleeve nuts (usually used to attach two pieces of threaded rod together) that had an OD of 5mm.
I was going to get some 3mm alloy stock and make the strap eye from scratch, but I found these MagDeal 1" alloy webbing adjustable buckles on Amazon that could be modified (it also turned out they already had a 5mm mounting hole in them too). I cut off the top part, reshaped the outer profile to resemble what can be seen in the screencaps and enlarged the slot so it would take the thick shoulder strap of the holster.
Next update will be progress with the inner plate.