[Tilt]

Any of you have any experiance with the 223 subs? How much PUNCH do they have at say 50 yards? Shooting them out of AR with a 1:7 twist 20" barrel, will they stabilize?

[robocop10mm]

The problem is that most subsonic rifle ammo is made with very heavy bullets. 80 grains is about the heaviest I have seen for the .223. To keep it down to subsonic level it will be a very reduced load. Reduced loads have their own inherent dangers.
A 1/7 bbl should stabilize an 80 grain well enough. 80 grain bullet at subsonic velocities will be anemic at best.
80 gr subsonic will not cycle an AR-15. I have played with a friends AR in .300 whisper. Quiet, subsonic, abt 2 moa at 50.

[Tilt]

I realize it may not cycle in an AR, I was just wondering how much energy they had at that distance. Would it be along the same lines as a 22lr?

[robocop10mm]

The 80 grain .224 bullet at 1000 fps has 177.61 fp of energy.
The 40 grain .22 lr at 1200 fps has 3.19 fp of energy.
The .380 pistol 90 grain bullet at 950 fps has 180 fp of energy

So, the subsonic .223 has about the same energy as a .380 but with the superior bullet shape, the .223 will have more retained energy at 50 and 100 yards.