Thanks guys, I'm not worried about the plastic in the barrel or anything like that. What I'm worried about is the overbored section where the barrel is ported. It has a lot bigger I.D. than the bore does but then it constricts again right at the very end of the barrel. It's over bore diameter but a lot smaller than the ported section. Not sure of the actual dimensions, digital calipers battery is dead and my brother has my dials.
The thing I'm concerned about is when the plastic cup reaches the ported part if it will exit thru the constricted area at the end of the barrel cleanly or if it might get a little crooked and cause a potential problem? (ie. weapon, shooter, bystanders)