Is it jamming or not cycling? If it's not cycling try to adjust the ring. If it's jamming, is it new or old? if old, how old?
Have a friend who got her Grandfathers A5 16 ga and the serial # traced back to early 1900's. The cahmber is marked 2 7/16" shells. Modern shels wont eject.
take the wood off and show us a pic of how the spring/friction ring is setup.
It probably looks like this
But needs to look like this.
It is possible it has the wrong spring in place if someone replaced it with the wrong one. How does the magazine tube look? Is there a lot of rust on it?
And you mention safety in front of trigger... Is it an X serial number gun or just numbers? If its a pre-47 gun its possible it has a 2 9/16 chamber instead of 2-3/4".
Like Poke81 said, check the friction ring setup. Also check to see if it actually says Sweet 16 on the receiver. If not, it could be older and have the 2 9/16" chamber. Not a big deal, but they need to be 'let out' to chamber current shells.
I have two 12 gauges. One wouldn't even start to eject. I totally disassembled and it was caked internally with soot and crud. After cleaning, oiling, and properly adjusting the spring/friction ring setup, it would eject but not cycle. So, after some reading online, I found that a VERY light coat oil (like wipe some on and wipe off with a clean cloth) on the magazine tube allows the barrel to move more freely to eject the shells. If you put too heavy of a coat it can be too much recoil and too much force on the action. You want it to be just enough to cycle. No more.