I always liked the idea of using a slower pistol powder for .223 in shorter barrels and being that I'm fresh out of cfe223 and have plenty of blue dot I tried to find someone that has used blue dot in .223. I stumbled across this

From most barrel length tests I have seen most 55gr bullets start to loose velocity after about 20' of barrel, and most .223 loads in 16" barrels get around 3000 fps on a good day. Anybody actually try this with blue dot? As far as cycling the bolt on an AR I'm sure there is much less gas, (and muzzle blast/recoil, not that a .223 has much anyway) But I've got plenty of blue dot, 55 gr fmj, and time.

[Winchester 55 grain FMJ

4 grs: 896 fps
5 grs: 1264 fps
6 grs: 1568 fps
7 grs: 1825 fps
8 grs: 1994 fps

9 grs: 2201 fps
10 grs: 2328 fps
11 grs: 2453 fps

12 grs: 2677 fps
13 grs: 2821 fps
14 grs: 2915 fps]

These were worked up by people wanting reduced loads for varmint hunting in 26" barrels