I agree with Ted's recommendation to use Dean Harris for choke and chamber work. One great thing about him is that he is so accessible by phone. He will take as long as is necessary to answer your questions and listen to your needs and concerns. He lengthened the chambers on a 20 ga. Sterlingworth Ejector gun for me, opened the chokes to my requirements, and tested the gun for regulation. In the process he determined exactly what load the gun was regulated for, and called and explained all that to me.
I hope he's around a long, long time.
SRH