If you're really keen on developing precision handloads for the AR-15, I recommend Zediker's excellent books - Handloading for Competition, and the Competitive AR-15.
In a nutshell:
- he likes W-W brass.
- match bullet weight to twist rate and to application - loading for 200-300 yards is a different load than for 600.
- don't screw around with seating depth - load to mag length - overall length
- use thicker primers - CCI as mentioned by another poster, to reduce slam-fire risk
- don't expect more than a few reloads from brass in either the AR-15 or M-14 due to the violent ejection - he doesn't anneal (I do)
- watch and trim cases carefully - a safety issue
- crimp or use enough neck tension to avoid bullet setback in magazine from recoil of previous rounds or even due to chambering (decreases seating depth)
Great thread!