23. Denix's Coachgun


                    The Conversion Process

I've just completed my project to convert Denix's Coachgun to fire PFC caps. It's relatively straightforward and was achieved with ordinary DIY tools - although a couple of the tasks were made easier by using my small lathe and miller.

Firstly a word about the Denix itself, the castings and construction are of reasonable quality and the actions are crisp. There is a little slop in the break action when the barrels are closed but its fairly minor quibble. Overall it feels good and solid.

Given that the Denix has functional external hammers, working break action and hollow barrels this meant a lot of the groundwork is in place - thanks Denix!

I have an MGC 31-RS2 and intended to use the shells from that for this project, being fully prepared to have to bore out the breach area for them to fit. As it turns out the shells drop into the barrels no problem, in fact they go quite far in.

Using the RS2's detonator area as a template I made up two aluminium detonator chambers out of 20mm dia bar stock and the det rings out of 9.5mm solid brass bar. I bored out the brass to match the RS2's ring and profiled the rim to give a smaller surface area for more impact on the cap. The brass was then inserted in the aluminium and secured with a grub screw.
I then positioned these chambers in the denix barrels so that with a cap in the shell the bottom of the shell is flush with the face of the barrel. These were then secured in place with screws.

I then turned to the breech and drilled holes (3mm) through the fake percussion nipples out to the breech face and then enlarged the holes in the breech face to allow the nuts to recess into it. I then inserted 3mm cap head bolts cut to length and secured them with dome head nuts.
So now when you cock the hammers and fire, the bolt/nut is driven forward onto the back face of the shell and detonating the cap on the brass ring.
The way the breech closes means that even with loaded shells and the hammers forward the nuts just get pushed back slightly on closing.

On initial dry fire testing I found the shells got stuck sometimes so created an extractor out of some ally rod and thin strip. This was where the lathe and miller came in handy to drill the hole and make the slot.

I found the standard 5mm (Maru or MGC) caps didn't seem to work very well, maybe due to the detonator rings and/or insufficient striking force from the Denix hammers - probably more the latter. So given the 7mm caps are more easily deformed due to them being more 'open' I milled out the top of one of the shells to accept a 7mm cap on one side of the 'X' (you can still put a 5mm on the other side). Again I used a 7mm flat ended milling bit on my miller to do this.

The Marushin 7mm caps fire far more consistently and produce plenty of sparks, smoke & noise.


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