Many reloaders use the Lyman type "M" expander for their AR15 rifles and bump the case mouth onto the .226 section. This aids straight inline seating and reduces neck/bullet runout. If needed a taper crimp die can be used to close up the case mouth for proper feeding. Normally after brass spring back the case mouth is only .001 larger than bullet diameter. My main point being the Lyman expander is .221 and .003 smaller than bullet diameter.
Below is from a test of .223 resizing dies and how much they work the brass, And you can see the inside diameter of the case neck using the expander and the amount of bullet grip.
And below the RCBS AR Series dies come with a taper crimp