Problem with shooting actual .38 Spl ctgs in a converted .36 Navy. The .36 Navy actually uses a .375 ball. 'When you load it you'll notice the chamber shaves a thin ring of lead off it as it's loaded. The bore is actually about .370. A modern .38 has a .357 bore, meaning you've got about .013 of windage between the modern .38 spl slug & the rifling of the .36 Navy bore. The old .38 Colt ctgs--Long, Short, & New Police--used a heel-type .375 slug, with the lube grooves outside the ctg case like a modern .22. When you shoot modern .38 slugs in one, unless they're hollow base & very soft lead, you'll get keyholes if you ever actually hit the target.