Jefferson State airgun .357 Has a M14x1.25 thread on the barrel. I recommend the Ronin .357 M14x1.25. This will be a special request for this configuration. This will be #S21 with a M14x1.25 cap
https://donnyfl.com/collections/ldc/products/2-x-6-5-inch-ronin?variant=13286078251051
Any .30 and lower is 1/2x20 threads I recommend the Sumo .25/.30 1.2x20 #S9.
https://donnyfl.com/collections/ldc/products/1-5-x-6-5-inch-sumo?variant=37719183748