Crossman 180 CO2 Leaking out barrel

I recently bought at vintage crossman 180 at a yard sale for $15. It was in ok condition but after putting a CO2 in and cocking and puncturing the CO2 it leaks out of the barrel and around the breach. I took the gun apart and replaced all of the o rings and cleaned and added new lube. It leaks a little less but still enough for it to be audible and empty the cartridge in a matter of minutes. Do you have any suggestions for what I should do next?

I'm not willing to spend the time and money to send it to Crossman as that out of my budget I want to spend for this gun. 
 
Did you cock the gun befor puncturing the co2.

Leaking down the barrel is cup seal leaking.

If the hammer is pressing on the valve it doesnt build pressure fast enough to seal.

If the gun was cocked then you probably have a scratch on the valve or cup seal. Both can be catefully polished out. Cup seal can be replaced inexpensively.

Not familiar with this gun in particular but rebuilt plenty of co2 guns over the years.