My Accura uses the BH209, and the W209 primers pretty good. Most of the time ignition is instant. There have been a few times where there has been hangfires, and once there was a misfire. My Accura has been left loaded in some pretty cold temperatures and for extended lengths of time during hunting season, and still been quite reliable.
I started out using crush rib sabot, but seemed to get hangfire, so i swtiched to the Harvester smooth sabot, which is tighter.
I do get hangfire when the breech plug fire channel gets carboned up, so i drill out the carbon with a 7/64" drill, which makes for more reliable ignition.
I have considered trying a magnum primer, but haven't gotten around to it yet. However, i am in the process of modifying the breech plug so that it more closely resembles the breech plug in my Omega. My Omega, has never had a misfire, or a hangfire with BH209, and W209 primers; it has endured weeks without cleaning and temperatures as low as -19*.