There are no hazmat fees for shipping a reloadable motor casing, only the reloads...
It's nowhere near that clean of a distinction.
Some reloads are deemed HazMat label and surcharge worthy, others are not.
The distinction is not even made based on the size of the motor, but the weight of each individual APCP puck (30g per maximum, IIRC).
For example, AT H130W motor is cut into 6 individual pucks/grains of ~20g each (pic #1 below), and can be shipped HazMat-free.
Very similarly impulsed H123W is cut into 4 pucks of ~32g each (pic #2 below), and has HazMat designation.
Net-net: the HazMat designation is somewhat capricious.
I don't see the logic of how shipping 6 pucks of APCP in one tube presents more or less of a flammable threat, than 4 pucks of similar total weight.
But it is, what it is.
If it is a Haz Mat motor buyer is in just as much trouble as seller if caught.
That's not true.
Proper packaging and shipping designation is 100% responsibility of the shipper.
An average buying is in no position to comply with the shipping rules, nor enforce them, nor be responsible for any such compliance in any given jurisdiction.
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