I'd love to have more photos of this rifle in case I can do another edition of Michigan Gunsmiths. Also, exacty what are the markings on the barrel?
Here is what I have in the current edition:
Berger, Caspar, Detroit 1836 - 1866
Wayne County 1850 census shows Caspar Berger 46(?) Gun Smith and his wife Margarett 39, both from Germany. Their four children, Matilda 14, Margarett 13, Joseph 9, and Caspar 2 were all born in Michigan. At that time the value of his real estate owned was $800. The Detroit Advertiser for 1836 reports Berger as a rifle and gun smith, shop on Woodbridge Street, 6th door west of Steamboat Hotel, 183612. Active in Detroit up to 1866. Several percussion rifles with his name are in existence, and at least one 10 gauge double shotgun. This shotgun was said to have been made in Berger’s shop at a Plum St, Detroit, location.
The city directory for Detroit in 1866—’67 lists Caspar Berger as an engraver, boarding at 46 Russell. A Joseph J. Berger, boarding at 46 Russell, is also listed as an engraver.
The Berger rifles of which I have photos are later half-stock rifles. I'd judge yours to be early, as in sometime in the 1830's. Whether or not you choose to risk a few fingers & a fine rifle do NOT use 200 grains of powder in it. Original loads tended to be very light by today's standards. Maybe 40 or 50 grains.
No one can tell you whether it is safe to shoot as no one, save a place with a magnetic particle inspection machine, can tell you if the weld is sound. Weld, yes, old barrels like this tended to be forge-welded wrought iron. A lot of them were very good. Some were not.
I don't really collect Michigan guns anymore, though you could tempt me, but I sure do like to gather information and photos of them. Would like your permission to use these two photos in my future publications.