reloading 8x72r ammo for a drilling

Been reloading for many years, however that means that i know how much i don't know. The gun was given to me by a friend, and is a good match for the hunting here in Florida.The Drilling was a bring back from WW2 and has set in gun safes for all this time.It has honest wear from use but no big problems. Spec's are 65mm 16 gauge barrels, 21.75 inches long, choked imp. cyl. in the right barrel, and imp. mod. in the left. Rifle barrel is 8mmx72r (a box of original cartridges came with the gun, and they chamber correctly and the chamber by observation is the same.) I will do a chamber cast before i go further in loading. Slugged the barrel and to my best measurement it is .323 groove diameter. Barrels will close on a sheet(strip in each chamber)of typing paper but they are tight on it. No wiggle between barrels and receiver without the paper when i try by hand.Set trigger for rifle barrel. The word nitro in the proof marks so i think that is 1910 and later. Still working on the rest. I believe it is a Guild gun at this point, but will have it looked by a higher authority on german guns. I intend to take it to the woods and let it speak to some of the local game after a few small repairs (bent front site, and cracked horn trigger guard). Any thoughts from the readers would be welcome.