Speer recommends their use with ball powder. I`d drop a grain and see how your load reacts if you have a near max load already that you plan on sub`ing them in.
I use 450 primers with ball powder in my AR. I use h335 with the 52-55gr bullets and BLC2 with the 68gr bullets. I have shot the 52gr amax and 55grvmax with the h335 and 68gr bthp match Hornady bullets with the blc2. These bullets all shot exceptionally well from my AR!!!
I don't have and answer to your question. I don't remember how standard primers worked? I've been using small rile mag primer for loading hundreds of thousands of .223 Remington for the past twenty years. These of course were all loaded with the AR customers in mind.
The CCI 450 primer uses the same cup as the std CCI 400 small rifle. The difference is in the priming compound. Spper has a No.41 primer they developed specificly for the 5.56 cartridge with a Mil-Spec sensitivity level to prevent slam fires. They can, according to Speer, be sub`ed for the data useing their CCI 450 primer.
Remington also, I have heard, developed their 7 1/2 small rifle to replace the 6 1/2 small rifle primer when they 1st developed the 5.56 cartridge for the military, due the same thing. That is a slightly tougher cup and is a mag type primer.
Speer also has a No. 34 large rifle Mil-Spec primer.
I use the CCI mag primers. I have both, but according to what I read, the mags have a thicker cup. They show less pressure out of my savage bolt gun and I just bought the last thousand I saw.
Joe