Silencer help

[marsattacks]

I don't claim to be a good mechanic but this should be easy. It hasn't been. I have a 78 MC5 400 with the stubby pipe end.  This bike is loud. I've been trying to get the "silencer" end to slip out of the pipe but it won't budge after plenty of PB Blaster. I don't want to wrench whip it but I might have to. Is there a trick?  I'd like to pack it or add a Supertrapp. There isn't much room for any packing as is. Grateful for any ideas before I booger something that has survived a good log time and doesnt really deserve to be abused.  

BTW, this is the pipe w/ 3 6mm screws holding in the end cap and they are out of course.  Thanks, John