Custom Airguns?

I read that Gary Barnes doesn't make anything anymore. He just did extreme big bores anyway.

Chip Smith only really makes stuff for himself and his friends as a hobby. He has a website where it lists a custom breach but I doubt you can just go order one unless something has changed since I last asked him about it. 

There are various places that make "custom" air guns from the Crossman frames. These are more made to order than custom though.You won't come away with a one of a kind.

I think of custom as being something unique made to my specs. Made to order is me choosing from a catalog and it being made for me (possibly with some catalog options I can choose). RAW and WAR are made to order although they describe it a custom. 

Custom benefits me. Made to order benefits them.

I don't know of a single genuinely custom air gun maker on planet earth. Not one who sells to other people anyway.

There are a few modders who will modify existing air rifles for you though. It's usually the people who offer tuning services. If you want something turned into a target gun or a caliber that isn't normally available, they can do stuff like that.