I've just recently inherited a rifle from my passed away grandfather. It appears to be a H&H .465 SxS "Royal Hammerless Ejector". The rifle has been left uncare for a long period of time but still in excellent condition. Without proper knowledge & carefulness, I tried to clean and oil the rifle by taking off the foreend, barrel & receiver. However, I accidentally dryfire the receiver portion before assemble all the parts back together. The rifle (only receiver part) then turns to UNCOCKING state and that makes me unable to put the foreend back in its place. So now I can't assemble those 3 parts back together and feel so worried about it.

I'm writing to ask for help because this rifle is old and no one seems to know or understand its mechanism. Is there a way to make the rifle in COCK position again so that I can put the foreend back in?

Any advice or suggestions will be greatly appreciated. Thank you very much.