I disassembled both weapons, laying aside the unneeded parts. Then, claying the openings that would cause problems with making the mold, I proceeded to clay line each incorporated gun component into mold boxes, and then cast RTV molds around these parts.

Once the molds were cured, many sacrificial castings had to be made to use as working prototypes.  I knew that quite a few would have to be cut up while working out all the fit and features we wanted.

We know that the original Steyr bolt could not have been used in the hero prop by the fact that what can be seen though the ejector port of the gun and what shows up in the stunt castings has none of the features of the real part.  Neither the shell extractor arm nor the two small holes in the Steyr part are present.  Instead, the stunt prop bolt has a long groove machined into it, which is not a feature of the Steyr or any other bolt, but makes for nice decoration.

First I turned out a couple of test bolts using Delrin ®   in order to get the right fit and work out details.  Working with a softer plastic made for faster cutting and sanding.

Then I began machining a slot in the underside of my new bolt to allow clearance for the Bulldog’s frame.  I tried to use the locking lugs of the real Steyr bolt locking system but found that the molds could not handle the severe undercuts of the inside bore of the Steyr receiver.  Regardless, when I determined how much would have to be removed from both the bolt and the locking lugs, I found there would be so little left that preserving the feature was of little practical value.

Once I lined up the Steyr receiver with the Bulldog over the stunt prop, I could see that, for the Bulldog barrel to line up with the centerline of the stunt prop barrel, the Bulldog would have to cut about halfway into the centerline of the Steyr receiver and bolt!

 

 Ideally, the blaster model would have a working bolt with cocking lever action.   We could discern that, at the very least, the cocking lever was able to move some on the hero prop, for it can clearly be seen to swing out  in the film scene where Deckard drops it onto the street while being chased by Batty.

At this point during the project, we had not yet located the original propmaker to confirm the functionality of the bolt.  Either way, I believe it makes for a much more realistic model to have various working components, and the bolt action is one of the truly prominent features of this fabulous weapon.