[Tim R]

Give your size die another quarter to half turn down. For some reason 223 is more difficult to size than 308. I load for a match AR. I don’t like to be embarrassed at a match because the Ammo won’t fit.

So, I check a few sized cases at random to make sure they chamber and eject with ease. I use mostly RCBS dies for loading rifle and have not had a problem with the neck not holding the bullet tight enough. For 223 I currently use a Hornaday bushing die which allows me to set the mount of neck tension.

Are you adding some crimp to your finished round? I typically don’t crimp rifle unless it’s going in a tube magazine such as 30-30. I may put a light crimp if the other caliber bullets have a crimp groove just to make things look right. The use of a heavy crimp can loosen the neck up. Worn out brass will not hold a bullet either. After I’ve loaded the ammo, I make sure these rounds at random chamber and eject with ease. (carefully of course) I also have seated the bullets to clear my magazines a few thousand’s for reliable feeding. I don’t get all hung up on OAL’s. In some rifles, not including your AR the bullet maybe pushed into the case because the bullet is being pushed against the lands of the rifling. (Most times though, the buullet is pulled from the case on extraction and a big mess is made from the now loose powder.)

Since you are loading for a AR I would be aware Federal primers are not a great choice. AR’s have a free floating firing pin. Once a round is chambered and then ejected without firing you will note the primer has a small ding in it. This is caused by the firing pin hitting the primer and putting a “Dimple” in it. There have been reports of slam fires using Federal primers. A better primer choice is Remington 7 ½’s. They are rated as magnum bench rest primer and work very well in the AR.