Turtlehead said:
The AR barrels are 1:7 and 1:8 so I am using light bullets.
That's backwards. Faster twist is for longer bullets. The 7" is specifically to stabilize M856 Tracer bullets, which are both long and light (the worst combination and hardest to stabilize). So you are spinning your light short bullets a lot faster than you need to. That increases errors caused by any mass offset in the bore.
To overcome that, you need to load straight cartridges. A bullet that is tilting in the chamber can keep up to a couple tenths of a degree or so of that tilt by deforming slightly on the way into rifling in the bore. This is enough to open groups up an inch or so with proper twist, and more in inverse proportion to the pitch of still faster rifling.
Tilting bullets have two causes: Case necks pulled off-axis by the expander in the sizing die during sizing, and seating that isn't straight.
I'm going to guess that your sizing die uses a conventional expander. These can be very hard on case necks by pulling them off-axis (see
this video). (That collet die in the video is for neck-sizing-only, so I'm not recommending it for your AR. It's just to show the principle. I use one in combination with a Redding body die to size the lower portion of the case when I want super-precision ammo, but that's a bit awkward to do on the Dillon.)
On the Dillon press it would be easier if you got a sizing die that uses different bushings and picked an insert that makes the ID of your case necks right without needing to expand them, so you can remove the expander and leave it off. This can mean changing the bushing for some brands of brass or when necks get work-hardened. Redding has bushings in 0.001" increments where other makes are in steps of 0.002", IIRC, but you may find the right one that way anyway.
For seating, the Redding Competition Seating Die is impossible to beat, IME. It has been tried against numerous other seating dies and produced smaller groups on targets, including as compared to other match seating dies. For a progressive press, it's a good choice.
I never crimp my rounds. You should experiment in your gun and see what gets best results.
Seat your primers hard. You want them to go in an additional 0.002-0.004" after the anvil feet touch down on the bottom of the primer pocket. This sets the bridge and maximizes performance and consistency. It is very easy to under-seat primers in the Dillon presses, IME, so you want to hand inspect that they are all below flush with the back of the head.
Remember that manufacturers can control primer seating well and that their brass is new so it's necks aren't bent. If you can get those two things under control, I think you will have made an initial improvement.
As far as your powder choice goes, Hodgdon's own burn rate chart has it slower than BL-(C)2 and 4895 and 4064. The military had H335's parent powder developed because the parent powder for BL-(C)2, which was developed for 7.62 NATO, proved too slow for 55 grain bullets in the AR platform. So I think CFE223 is probably going to do its best work with bullets 69 grains and heavier. It may be best with something like the 77 grain Sierra MatchKings.
In general, the fastest burning powder that safely achieves a given velocity has a shorter barrel time than the slowest powder that achieves that same velocity. For 52 and 53 grain MatchKings, Sierra has Vihtavuori N133 listed as their best accuracy powder. I've also seen Reloader 10X do well with 55's and Reloader 7 is another one Sierra liked for 55 grain bullets. I would consider trying one of those.
