Before anyone spends money " improving" the priming ignition on their rifle, please take the time to fire a primer only on your rifle at night, with the barrel pointed down towards some grass or leaf stems and leaves. You should see a flame come out of the barrel of your percussion gun, no matter how long it is, that will be at least 10 inches longer than the barrel, and the air pushed in front of the blast will blow over the grass or leaves. Don't do this with dry grass, or you may start a small fire.
The current primers are more than hot enough to ignite a dry powder charge of real Black Powder. I can not say the same with some of the substitutes, which admittedly have higher ignition temeratures.
The problem with using magnum primers in anything( no matter what they are called by a manufacturer) is that the primer itself may actually push the PRB or conical down the bore a short distance before the powder is consumed and turned into an expanding gas. When this happens, you will get a wife variation is chamber pressures, and a resulting wider diversity of velocities, shot for shot. Remember, with the PRB, there is not much contact being made with the barrel, or inertia, to overcome. The last thing you want in a PRB gun is for the ball to be moving up the barrel differing amounts, depending on the strength of that magnum primer, and before the main charge gases expand and begin their push down the barrel.
As for using modern primers in percussion guns, psitol primers have been used with a similar device shown above, by the under hammer slug gun shooters for years. Yes, it does take more time to load and fire the gun, because you have to unscrew the cap, remove the spent primer, replace the primer after loading with a new one, and screw back on the cap again. But, it does retain the primer, and the slug gun shooters, particularly in the larger calibers, get very even, and small SDV from their guns. Because the primer goes directly into the barrel, the slug gun shooters have no need for rifle primers. On a side lock, particular ly those with a drum and nipple arrangement, you may have to use rifle primers to get consistent ignition. I doubt it, but it would be something to try out over a chronograph. Standard pistol primers are very hot as they are. I again see no reason to use magnum primers, and at least one good reason not to do so.
