Just a FYI

Rem STS primers are the shortest USA made primers
Win209s are the longest and have about the same energy as a Rem STS primer.

Measure the flash hole of your plug. If its .035 or larger its time for a new plug. Your flash CHANNEL needs to be cleaned with a 1/8th drill bit. Any other method is pretty much a waste of time trying to get out hard carbon. As flash channel volume decreases, pressure that reaches the primer increases.