First make sure you have the plug installed properly acording to the book. sometimes they are just not in right and bind or catch a bit.
If it is in right just trim it very little at a time until it works and then make sure you can not insert more than 2 of the 2-3/4" rounds into the magazine or they will nail you for it.
CPL holder since 1991, NRA Lifetime Member, DU Member, NICET certified
"For those who would give up essential liberty to purchase a little temporary safety, deserve neither Liberty nor safety.—Ben Franklin.”