.223 Subsonic loads

I played around all day trying to figure out a good subsonic load for .223. Well Unique powder with a 60 grn Hornady SP bullet did not go so well. I had to drop all the way down to 3 grns of powder. Sometimes the primer would not lite the powder and I was left with getting a bullet out of my barell.

I knew that putting that small of an amount of powder in a case that size could cause that exact problem. I decided to try and go with the slowest burning powder I had so I could put more of it. I have a can of IMR 7828 that is the slowest burning powder IMR makes. My .300 Ultra Mag loves it and a lot of it I might add.

I ended up with 6.5 grns of 7828 with the Hornady 60 grn SP bullet. The chrony average was 975 fps with a 20" barell. I tried a few through my M16 with the 11.5" barell and they were not subsonic 1275 fps. The powder charge is small enough that it burns up long before the bullet leaves the 20" barell. The 20" barell gives the bullet time to slow down before it leaves. I don't have a 16" barell to test but would be willing to bet it would work fine if you backed the charge down just a little.

I didn't waste my time to see if I could get them subsonic out of my M16 since they obviousley do not cycle the gun. What the hell good is a MG that don't cycle.

If anybody else has any subsonic .223 loads post them.

No loads to share, but some free advice:

Don't shoot the bullets with the spitzer points or boat tails through a suppressor. Those supersonic drag reducing features are actually counterproductive at low muzzle velocities. These tend to pitch and yaw right out of the muzzle and that's hard on baffles.

A special high twist barrel with a heavy crimp and a 82 grn projo might get you more impulse energy to cycle the gun. However, I'd strongly suggest a blunt nose projo with a flat base. This is advice given to me by a person who has a commercial business making subsonic rounds for police and military. He's got the high speed photography of the transition ballistics to back it all up.

When downloading centerfire rifle cartridges, one needs to be mindful of detonation which can and does happen in undercharged cases with hot primers. Fillers aren't really an option for suppressed use. 7828 is a good choice of powders - especially the older stuff with the longer "pencil lead" grains. My 300 WBY Mag loves it too! It's a beeoch to meter though.

You can experiment with different bullet profiles and recipes, but at the end of the day, it's like building a glorified .22LR with a oversized case.

Here's a good read on subsonic projectiles.
http://members.shaw.ca/cronhelm/Subs...BC2C1156923879

3-4gr Unique or Titegroup
55gr soft point flat base
suggest magnum SR primers

keep a rod handy in case one gets stuck