One of our teaching M/L's , is a CVA with drum and nipple. When it starts to get dirty, it will let you know by giving you hang-fires as well as mis-fires. Under those conditions, it's really not a problem and in fact, welcomed as we use it as an example of what is happening and can happen. I'm sure that the magnums would work better but that would be treating the symptom and not the cause. As stated, the cause is fouling. Some of these drums have smaller channels. Sometimes the timing gets tight as we have to clean between classes. It's kind of neat, the way students start noticing the hang-fires...
Be Safe !!!