Alectia

Nylon threads are strong, inexpensive, and easy to use with leather. I like to use them when I work with belts. As was said by other members, nylon is better for products that are not going to be outdoors (for a long time). Polyester is a better choice for anything used outdoors because of its sunlight (UV) and mildew resistance. I think you can try polyester because you are going to sew rifle cases and dog leads. You can read more about nylon and polyester threads here https://www.superiorthreads.com/education-thread-for-sewing-on-leather and if you will choose polyester you can find more about brands here https://sewingland.org/best-sewing-thread/. As for me, I'm using HAITRAL polyester threads when it is needed.

Great job! It looks amazing!