http://www.ups.com/content/us/en/res...hip/hazardous/
Its Charged per Physical Package ..
Primers are supposed to be shipped seperate from Powder and both require a Haz Mat Fee
some companys decide to skirt the rules and ship both together.. At least till they get caught and then they will have He@@@ to pay .. The fines are no joke
some of the larger companys will wave a second or third haz mat if THEY have to ship from separate locations .. They are still paying the charge just not passing it on to you .. That's their decision
I know all this as I am a Haz mat shipper not just guessing ..
UPS charges the shipper $27.50 per package up to 100 LBS
..