[palmer]

The only reason they were plastic is so they could be mailed. Nobody makes pipe bombs out of plastic because they won't explode, just flare. The flare could hurt someone standing in the wrong location. But these "bombs" also lacked detonators or a large source of heat.

The guy is clearly loony, and his 2016 conversion to rabid Trump fan is suspect. But the simplest explanation is this was a terror attack (not a bomb attack) that was exactly like the fake ricin attacks on Trump's family, Collins's family, and a variety of DoD officials. It should not be overblown and characterized as a potentially lethal attack because it was not.

[kabar]

The only reason they were plastic is so they could be mailed. Nobody makes pipe bombs out of plastic because they won't explode, just flare.

According to the bomb experts, PVC is too weak to create the needed compression to generate the desired explosion. Metal is needed according to the experts.

The "bomber" didn't know how to make bombs. I doubt he even considered the mailing aspect of plastic. He was just making a Hollywood prop. FYI: There are plenty of metal objects that are mailed thru the USPS.