Colorado

Obviously you are not the first person to consider the .577/12g cape gun concept! Maybe not as a specialised "Leopard Rifle" though.

Here is the gun for you:

W.W. Greener shotgun / rifle combo Cape Gun

WW Greener no. 70571 combo 12 bore shotgun by .577 rifle. Originally a 12 ga SxS shotgun, it has been converted to a Cape gun and is in excellent rebuilt condition. Based on the Empire action with a new mono block, the work was completed 2 years ago. With 24" barrels with 1 standing rear sight. Restocked butt and forend with excellent wood.

Weight is 10 lbs, LOP is 14 ž" over a Silver's pad. DAC is 1 1/8", DAH is 2".

This was a cape gun advertised for sale some time ago and featured as a "double of the day" on NitroExpress.com.