With the pin and ramrod removed, and the barrel seated in the channel, do you have some "spring" in the stock up at the forend?
You should be able to continuously compress and release the barrel by hand up at the end of the forearm and feel this. The distance that the barrel "springs back" upon release is almost the width of that pin. T/C engineered the rifle to do this...a primitive type of free floating perhaps.
If you cannot get any "spring" out of the barrel, you might inspect that hooked breech plug and the channel that it mates to for any rust or crud that may need cleaning on both these male & female parts.
If you do have this prescribed amount of spring, I would simply get a new pin from TC