H&H was located just south of Baltimore, MD. in an industrial park, back around 1979. Hoppy used to walk around with a large parrot on his shoulder. I visited his shop back then to have a barrel made in 45 cal, One of the few makers with a choked muzzle on a rifle barrel. Great barrels. nice wide grooves and narrow lands. easy loading and cleaning. The rifling wasn't so much round bottom, but was more like an oval laid on it's side. The radius of the bottom of the groove was larger than the radius of the barrel, like Harry Pope's grooves.
I recently saw an unused H&H listed on an online auction site for a whole lot of money, considering I paid $120 for mine back around 1980.
IIRC, a guy named Mike Bell shot H&H barrels and pretty much cleaned up at all the local matches.
When I visited his shop, he had the CNC machinery running and he was shooting a 22 match rifle from one end of the shop to the other and the machinery was running just below the line of sight. He also custom barreled a few Remmie repros for match shooters.