The making of the 1933 Hill air pistol prototype copy

[ccdjg]

Some of you have expressed an interest in how I made the 1933 Hill prototype pistol that was recently discussed in a couple of posts, so here is a potted illustrated account. If it sounds too glib, I must admit that I have left out details of all the cussing and sweating and the (too many) machining mistakes made along the way, and these can be taken as read. I am no engineer, just persistent. Everything was done on my old Myford lathe fitted with a vertical slide for the milling operations; tools and materials courtesy of Fleabay.


For me the starting point in all these build projects is to make lifesize copies of the patent drawings. This is easy with scanners and Photoshop, except for the fact that patent drawings never seem to give dimensions. So there is usually some guesswork involved. Fortunately vintage British air pistols seem to consistently use cylinders with an outside diameter of about 1 inch (e.g. all the Webley pistols, Warrior, Lincoln, Acvoke, Certus etc.) so it was reasonable to assume the same for the Hill pistol. The second stage is to work out how to build the principal carcase, which is often a major head-scratcher, as the pistol inventors always depict the carcase as a one piece steel unit. This is OK for someone with access to steel casting facilities, or drop forging, but is not helpful for the amateur, and so improvisation is called for. The carcase plan can be broken down into sections that can made from solid steel by a combination of hacksawing and filing, followed by brazing the pieces together. Precision steel tubing can often be used for the cylinder.


For the Hill pistol, this was how I dissected the carcase, with the intention to braze the various components together at some appropriate stage.






The first component to tackle was the cylinder housing block (A). As shown in the following picture sequence, this began as a rectangular block of mild steel.





The block was drilled with two parallel holes, one to accept the cylinder and the other the barrel. The drilled block was then milled to give two steps (pics 1 and 2). The slot for the trigger was then milled (pic 3). Producing the round profile of the cylinder required some thought, and the method finally adopted was to mill a series of closely spaced grooves longitudinally until an approximation to the circular profile was achieved, as in pics (4) and (5). Finally all the ridges were filed down to give a smooth profile (pic 6).


The next component tackled was the barrel housing block (C). Precision seamless steel tubing was sourced as the cylinder (B), and the block had to be attached to this very strongly, as it also had to carry the cocking lever pivot pin and would be subject to a lot of stress. It was decided to use a combination of brazing and pinning to do this, and the sequence of events to achieve attachment is shown in the next series of pictures. After cutting out the shape of the housing (pic 1) with the appropriate curved base to fit snugly on the cylinder, the base was drilled to accept two pins (pics 2 and 3). Corresponding holes were drilled into the cylinder to accept the pins, and the block was brazed tightly into place (pics 4 and 5).






The grip frame (D) was cut from a slab of steel. The upper edge of the grip frame and the lower edge of the cylinder housing (1) were profiled to give a dado -type joint ready for brazing.






With the basic carcase now sorted, the next stage to tackle was the particularly difficult one of the trigger guard/cocking lever. This had to be forked at one end, with the fork pivoting snugly against the cylinder and the muzzle barrel housing. It also had to have a precisely curved extension with a central groove to receive the roller wheel on the floating muzzle plug, as well as a second deeper slot to accommodate the cocking link. The approach used is summarised in the next sequence of pictures:





First, a slice had already been taken off the drilled cylinder housing (A), which had deliberately been made longer than necessary for this purpose, and was then cut to be a perfect fit around the cylinder and barrel housing (pic 1). It was drilled through to provide the cocking lever pivot holes as also shown in pic 1. It was then cut into two halves to provide the two jaws of the cocking lever (pic 3). A slot was milled in the end of a square section steel bar, which would form the cocking lever, to provide a track for the roller wheel of the floating muzzle plug. The bar was hot forged to give a curved end (pic 4). The two jaws were drilled for pins (pin 5), and the jaws then pinned and brazed to the end of the cocking lever, as shown in pics 6 and 7. Further heat bending of the of the bar and trimming was carried out to form the trigger guard (pics 8 and 9).

The floating muzzle plug was turned down from steel round bar and consisted of three sections: a long narrow section which acted as a spring guide, a short wide section that was a sliding fit in the cylinder, and a short narrow section which carried a small roller wheel. This is shown in the following picture:





The piston was turned to size, slotted and a notch added for engaging with the sear.





This next picture shows the various components loosely fitted together, including the roughed-out trigger and the cocking link, which was made of heat hardened steel.







The trigger/sear/safety unit was a particular problem as the patent gives no information about it for the pistol. One can infer the general principles from the information that is provided for the rifle version, and the position of the pin holes in the drawing of the exterior of the pistol help define the relative locations of the trigger, sear and safety components. The shape and size of these components is very critical, as all three have to act in perfect unison. This had to be worked out from scratch, and involved a lot off head scratching and trial runs. Eventually a satisfactory conclusion was reached, and it actually managed to improve on the original by enabling a simple coil spring to be used instead of the special horseshoe spring used by Hill in his rifle, which would have been very difficult to insert into the limited space in the pistol. This shows the shape and positions of the three components, which were made of tool steel and were finally heat hardened :






The breech closure was next considered, and was based on the drawings shown in Hill’s second patent. This consists of a sliding gate, which is locked in place by a cam lever.




The barrel had been turned down from an old air rifle barrel and his was reversibly locked in place above the cylinder by grub screws let into the barrel housings at the breech and muzzle.

When all the major components has been finished, various smaller tasks were undertaken, such as drilling the air transfer port, shaping the front and rear sights, drilling and threading holes in the grip frame for the grip plates, making the grip plate screws, making the spring-loaded catch in the grip, making the cocking lever pivot screw, and finally making the walnut grip plates themselves.







At this point it was necessary to think about any lettering I wanted to apply to the body. This needed to state the patent origin of the gun, and also needed to make it clear that the gun was a modern reproduction and not an original prototype. Having decided on what form this would take, the lettering was applied by electro-etching.







I then had to decide on the final finish to be applied to the gun. I could have gone for rust bluing to give a vintage look, or hot bluing for a deep black modern finish. I was also tempted to try nickel plating, for no better reason than I had never nickel plated a whole gun before and it seemed like an interesting challenge. In the end I opted for plating, as I also thought a plated gun would make a nice contrast with all the other guns in my vintage British air pistols display. I used what is called an “electroless nickel plating” technique as it gives a very strongly attached nickel layer, and uniform thickness is easily achieved on awkwardly shaped objects like this, unlike normal electroplating. With the grips varnished and everything put back together the final pistol, despite its rather ungainly chunky shape, looked quite smart.

[averageplinker]

Thanks for very interesting read. The end result is a testament to your detective skills, machining skills and patience.

[Mark D]

ccdjg - you my friend are a clever man

[Garvin]

Wow, John! That's incredible workmanship from a non-engineering pofessional. I'm not surprised this is the 'sanitised' version.

Thank you for going to the trouble of describing the process in this detail.

[ptdunk]

Excellent!

Fascinating stuff John, I'd have happily read through every single stage of production.

Thanks for sharing it and taking the time to document it.

I'll have to look up your previous projects!


Matt.

[Leonardj]

Awesome job !!
Thank you for sharing the details, process, and finished product pictures.

[Abasmajor]

Hello John,

Thanks for taking the time and effort to comprehensively document both the manufacture and performance of this fascinating little pistol.

I know you are a very busy man with many projects no doubt queuing for your attention, but maybe a short publication devoted to modern reproductions of prototype or experimental air pistols could find a place at some time in the future. I imagine you document the process as you go through the various stages, so maybe much of the preparatory work may already have been completed.

Thinking about it, maybe the best place would be in the relevant section of a re-issued Encyclopedia of Spring Air Pistols which would no doubt be very much in demand.

Regards
Brian

[ccdjg]

Thanks for your interesting suggestion Brian. Certainly food for thought. There are just two pre-1950 non-commercialised vintage British spring air pistol designs remaining for me to tackle, and if I can complete these successfully then I would feel reasonably qualified to write something that could be published. One patent is by Lincoln Jeffries and the other by Frank Clarke Lead Products (probably intended to be their Thunderbolt Senior), and I have made a start on the first already.

Then of course there are the American patents. Enough to keep me going until my lathe packs in!

Once the workshop has lost its appeal then it will be back to writing my second edition (full colour) of the ESAP.

Regards
John