NEED Help browning sliver

[total disaster]

I have a browning sliver camo 3.5 inch gun that the barrel comes on and goes on very hard do to the o ring in the barrel piece that slides over the magazine tube. how do I remover o ring and where can I get replacement ? its causing the gun when fired to barely blow the bolt back and jam a lot and its only jammed when barrel started coming off hard

thanks

Justin