For a few years, I owned a Holland & Holland single barrel trap gun made for the US market. It was a wonderful gun built on a boxlock type action. The one thing I didn't like about it was that it had no safety. It was made exclusively for use on the trap range. I had a discussion with H&H about having the barrel cut off and replaced with a monoblocked Paradox barrel. They were receptive to the idea but I decided to scuttle the plan because of the safety issue. Instead, ordered a new, bespoke, H&H back-action sidelock Paradox. I do not regret the decision one bit.
I am a great fan of the Paradox guns. I have owned more than a few. I currently only own two. One is the above mentioned gun. The other is an 1887 hammer Paradox. It was originally a black powder gun but it was reproofed for nitro and I sent it back to the H&H factory for re-regulation to the current factory ammo.
Still, I have always believed a single barrel Paradox gun would be a wonderful thing to have. So, I purchased a second hand Zephyr Vandalia single barrel trap gun with the idea of having it converted. It has a 32 inch, thick walled, barrel and an extra tight choke. The rib is ventilated and soldered to the barrel but the last 3.5" of the rib are not ventilated, that last long portion is solid. I planned on cutting the barrel to 29". That would still leave an inch of solid rib at the end of the barrel. I imagined getting the choke cut with ratchet rifling and opening the bore to .7355"-.7360", making it suitable for H&H Paradox ammo and bullets cast from traditional Paradox bullet molds. If the bore was gently tapered into the choke the whole barrel would approximate that of a standard Paradox gun. The barrel is more than amply thick for this.
The Vandalia is a true sidelock. The lock work is on one side and a decorative plate is on the other side. It has a very "British" sliding safety on top of the grip. The forearm is wide and flat, and the stock shape a bit of a Euro/American mix. But it is better to have too much wood than too little. I found a gunsmith who can reshape both forearm and buttstock into a very British configuration. It all seemed like a very good project. The killer was that I can find nobody who can cut a Paradox type ratchet rifling.
I mention the gun now because you mentioned you used to be in the gun trade. The guns are not uncommon and they usually sell on the cheap. There is no reason one of these guns couldn't be cut down to a 29" barrel without removing the rib. Then the muzzle could be modified for screw-in choke tubes. Any stocker could lighten and reshape the stock into a British shape. The guns are chambered and proofed for 3" magnum shotshells. The end result would be a relatively low cost, sidelock, single barrel, game gun.
Of course, there is nothing wrong with these guns just as they are, especially if you are looking for a very robust, full choke gun for high volume shooting.
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