Flintlock before using those primers carefuly read the package. You may not be able to load .223 Rem with those. If you do I assure you there will be problems. Namely pierced primers.
The standard non magnum Remington primers were developed for low pressure loads like .22 Hornet. At .223 Rem pressure they will pierce. I had 2 pierce in .221 Fireball loads.
It will say something on the box for the standard small rifle primers. It was printed on the side of the box for the brick that I bought.
I used them for small pistol loads which they worked great for.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.