His name is Domicik Carpenter. He used to have a website and offered quite a few different black powder cannon models from the 18th and 19th century up to some decent replicas of WW I type French 75mm in small to medium scales. He eventually cut his business way back and shut down his website. He fabricated his models with high-quality steel.
Here's a link to his YouTube channel where he's got many videos of live firing a wide range of his models.
Morecannonfab on youtube
I have 4 of his creations including one of the early breech loaders with the removable beer-mug type breech pieces
This one is smaller than the earlier one pictured. It's only 70 cal. They were called many names such as: "Murderer", "Base gun", "Sling", "Port-Piece", "Serpentine", "Culverin", and "Perrier". Some of these were mounted on the gunnels of the ships that brought the first settlers to Jamestown. Then they were moved ashore to defend the first fort the settlers built
Here's a golf ball caliber calibered model of a Union Civil War 13-inch seacoast mortar.
Here's a just-for-fun breech-loading WWII-style firecracker howitzer he made for me. These use two firecrackers to fire. One with its fuse cut short is loaded into the barrel with the fuse to the rear. Then a second is pushed in behind it. There is a small notch cut in front of the breech door at the rear to allow the fuse of the rear firecracker to stick up to be ignited. It ignites and propels the forward firecracker out of the barrel which goes off a second or two later. About half the time one gets an air burst.
I also have a tiny Dahlgren naval gun he made but don't have a picture of it.
Cheers