Fed 150gr 9mm SynTechs, Too Quiet in AP5

Shooting the MKE AP5 trying to show how quiet the syntech 150gr federals are. Also known as "red rockets" "lipstick" or "plastic" rounds.
They are coated in some red polymer, i figure they probably wouldnt do great if left in a hot barrel but they seem to do just fine. One caveat is i have to use HK made magazines to have these feed correctly consistently, the MKE ones are hit or miss.