ohihunter:
OK, I will solve the rest of the story here as none of the other posters [after me] have done so, and I am really disappointed in them...
The magnum primer is generally recommended for:
(a)igniting all ball powders as ball powder is "relatively"
harder to ignite than other [stick-type] powders and the magnum primer has a relatively much "hotter" flame than standard primers;
(b) especially recommended when igniting a ball powder in cold weather of 0 degrees F and below;
(c) igniting larger quantities of ball powder (think .338 Win. Mag, 22/250, 308 and 30/06, etc.)
See the older Speer manuals of 1970-90s vintage for a good discussion on this.
Thus, when switching to a magnum primer for a load previously worked up to a safe maximum, one should certainly back off the same powder say 10% and work back up to a safe level with the magnum primer, especially if the loads will be used in hot summer weather - i.e ground hog hunting here in OH - as the magnum primer develops higher pressure faster than the standard primer did with the same quantity of powder. So you can't just use a nmagnum primer withe the previously safe pressure load of the standard primer and expect the same pressure! You may very well get an overload/excess pressure, and you may not! Understanding this so far.
Notice none of the other posters have mentioned any of this...and I have other things to do than type...but have answered as these others do not seem to get it although you are the rookie reloader and they allegedly are "veterans"...
That being said, the CCI 400 standard primer has done very well at igniting my ball powder of choice (Winchester 748) so I have not opted to try the CCI 450 Magmum primer...in the .223 Remington as I hunt a lot in the summer and the 400 standard works fine. BUT, if hunting coyotes in sub-zero conditions I would do so with a Magnum 450 re-worked load. You will likely benefit with a more reliable, complete powder burn...relatively.
Oh, by the way, the BR-4 costs almost twice as much now as does the standard CCI 400 or the Magnum 450, so it is more than just "pennies" as one poster claimed. The BR-4 allegedly has better "quality control" manufacturing than the 400; let CCI tell you what are the other differences between it and the 400.