Trapdoor Rifles

According to all the information I can find a cadet should have a 29.6” barrel, a 45.7” stock and overall length of 48.92”. The rifle i have includes a 22” barrel a 40” stock from butt-plate to end cap, coming in at 43.25” total length. My serial number is 170508 breach block is marked U.S. model 1873 cartouche on the left side of the stock shows 1884.so I’m stumped and need help getting a positive I.D on this rifle.

Serial number in the 170000 range would be for the year 1881. You see 1884 cartouche on stock. Did you measure barrel by using a rod inserted in muzzle to face of breech block to get 22 inches which is correct length for carbine ? Sorry but it sounds like you have someones parts made up shooter that is nothing the arsenal ever produced. posting pictures would be of help.