The M4 is an easy one to load for, unlike the 17 Rem......
If you want to check for lower velocity nodes, start off with 15.5g of H335 and/or 322 with a Berger 25. Go all the way up to 19.5g and you will hit several accuracy nodes. Barrels can vary on their velocity at 19.5g from 4050 fps-3900 fps. My reamer is a turn neck zero freebore reamer.
If you love copper in your barrel, start off using Hornady 25's flat base. You can use the Horanday's with success, but you will pay the price scrubbing copper out of your barrel in all 17's that I have had including the 17 Ackley Hornet.
A buddy of mine swears that the AA2230 is the way to go on the M4. Some of my very best crow, squirrel, and rabbit shooting memories was with a freind's 17 M4 that had a pencil barrel on a Sako...we sure killed a lot of animals with that gun. Anything you pointed at at 200-250 yards was dead meat.
It will be interesting to see what the feedback is on the 17 Hornady Poly tip. It is possible that they have decreased the amount of bearing surface to make the bullet foul less.