Query: I inherited an English boxlock 12 gauge light game gun.The person who left it to me had a note in the hard case that said the chambers were 2 5/8in.Can I shoot 2.5in RSL SHOTSHELLS in it safely?Is there a simple way to measure the chambers,I tried to but came up with different lengths. It has all kinds of marks on the water table I can't read. Thank You!

H