I don't have much experience with small rifle primers, but as a general practice, I start everything off with Remington primers. The cups are relatively soft and show pressure very well. They usually shoot well, too.
If you develop a load with a magnum primer, and it shoots well, use it, but if you have a load using std primers, back off on the powder charge before trying a magnum primer. Not everyone agrees that this is necessary, but I would do it.
Watch the 748 loads. Friends who shot it in .223 matches told me that it dropped a lot of pressure in very cold conditions. That was several years ago, and may not apply now. They may have stabilized it.
The trick for me is to find a bullet the barrel likes, and a load with low std deviation, and get them together. You will need a chronograph.
Enjoy your project. Good shooting, Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time