If it was converted from a double trigger to a single has the bow been altered as well or is it as it was originally ?
Having converted a few guns to double trigger mainly to get rid of a troublesome non functional single trigger it is a lot easier than doing it the other way round .Being a box lock makes the job a lot more straight forward than if it were a side lock. All jobs like this would need to be well looked at first to ascertain any problems ,how much wood has been removed ,will the safe work correctly etc, before committing .
