I have a Midland hammer .410 double shotgun (made in the 1920s) that was converted by its original owner, a 'proper' gunsmith, for his own use. He sleeved it using old SMLE .303 barrels (hence the left-handed rifling) and chambered it in .32-20, so it is really a double Rook rifle. It is regulated for loads around the speed of sound. I did load a few up to 1900 fps but the regulation went to pot and it was reluctant to open because of the primers flowing back around the firing pin.

It is very happy with both nitro and smokeless loads. It is the hungriest rifle that I own because whenever I turn up at the range someone will say "What's that?" "I've never seen one of those before" "Can I just try a couple of shots with it..."

It is a project that is well worth doing. SMLE barrels are thinner than No. 4 .303 barrels, so make better tubes. I know experts will say that the rifling is too fast for that calibre, but it shoots!

Depending on where you are in Britain we could meet up at Bisley for a viewing - send me a PM. Of course you will need to have "Good reason" to get it onto your Firearms Certificate depending on which county you live in. .32-20 is easy to load and components are easy, really. Don't try it on wild boar, though; they will get really WILD!