Plastic stuck to parkerizing

[fastcarsgofast]

I got a police trade in shotgun. The inside of the barrel was coated with a super sticky plastic. After scrubbing the crap out of it I got the inside clean only to find that this stuff was now stuck all over the outside. Any idea how to remove it without ruining the parkerized finish?

 

[Spartan07]

Carb cleaner bro.
Or a torch?

 

[Kahrnut]

Try brake cleaner. Carb cleaner stinks, leaves a residue, and tastes terrible.

 

[Fatal_Bert]

Acetone