Like Echoes said, the e-tape needs to increase the pre-load on the spring, not the actually diameter of the plunger tube. Also, you may want to consider removing the 5c coin, and replacing it with a similar sized washer. You need to focus on reinforcing the outside of the plunger tube end, more so than the middle. Also, the washer allows you to add more epoxy.
Barricade's jam when you pull the trigger too fast. There's been some good explanations as to why, so I'll leave it at that. With the flywheel activation mod I've done to both of mine, I still pull the trigger slowly, and the pause between shots allows the flywheels to increase up to full rpm again.