Well last week I got the 22-4.10 it cleaned up rather nice it shows good aging not neglect

. I bought a box of 2.75" 4.10 shells and a clay pigeon slinger my 15 year old and I had a blast trying to shoot the clay pigeons (first timers) out of 20 shots we got two clays

it was fun but we need lots of practice.
forward sight is loose but will not come out any ideas how to tighten it up?
Can I date this gun it has no serial number?
On the barrel it says 4.10 bore, 3 inch chamber

what does 3 inch chamber mean in trems of buying shells?