While it is not exactly what you are looking for, you might want to take a look at a H&A style Buggy Rifle. The reason it is not exactly what you are looking for is because it is an under hammer. But, it is very accurate and nice and light. I made one from parts from Deer Creek Products in Waldron, IN. It's a .45 caliber and light as a feather. It's a sweet shooter, too. The ready to shoot guns are not plentiful but you do see them for sale occasionally. The action is very simple. If you want to build it yourself, contact Deer Creek Products and ask if they still have the parts. They will send the action off to Long Hammock to have the barrel fit to it. You can select the caliber, barrel weight and barrel length that you want. All that's is left is some minor woodwork and browning or bluing the barrel. It is an easy project if you are at all handy with some basic tools.