RE: "Double bang"
eb
Hodgdon has great customer service. Email them & tell them about your hang/misfires. As long as you did not get them wet, they will send you a container to place the remaining pellets in -- then send them back free of charge.
There is a binding agent in the pellets that keeps the grains intact. They may have applied too much (or) you may some Pyrodex mixed in with your 777. It's happened before... both powders are bottled & pelletized under one roof.
Around 10 days after you ship the contaminated pellets, you will likely receive 2-pks of new pellets to replace the one pack that went bad.