This is an old trick I learned a few years ago. I was shooting with about six other gunners and one of them asked how I got my gun to go bang so quick? He and the others would have to roll the slow match around in the prime powder a bit to get ignition. Some of you may have noted that a match cord won't always give instant fire.
I prime my vent in the normal fashion with BP and then I put just a tad of smokeless ball powder on top. I use ball powder because it flows easy and is less prone to being blown away by the wind.
So why does this work? Well, because smokeless ignites at around 160 degrees C and BP requires about 300 degrees C.
Go ahead, give it a try.
Bill
