223 Subsonic Cycling Load Data

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Haymaker
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Posts: 10
Joined: Sat Dec 01, 2018 3:57 pm

223 Subsonic Cycling Load Data

Post by Haymaker » Sat Oct 12, 2019 10:23 pm

For the past 7 months I have been trying to get a .223 subsonic load working with a standard AR15 platform that cycles. I tried to find some load data but had no luck. It seems a few others have tried this and ended up not having much luck either. Some of the load data posted that claimed to cycle an unmodified AR did not work for me.

I ended up purchasing some Atomic Tactical Cycling 5.56 NATO Subsonic Ammunition from Midway at $60 for a box of 50. Yes, I know, that’s expensive. I had high hopes for the sub ammo, but it didn’t work. I could not get the Atomic subs to stabilize with my fast twist 1:7 10.5” or 16” 5.56 NATO barrels. Atomic recommends a 1:7 twist or faster. The ammo cycled and locked the bolt open in both the 10.5” and 16” barrels. The Atomic sub ammo gave me around 1150 FPS from the 10.5” barrel and around 1500 FPS from the 16” barrel. Don’t waste your money on this ammo!

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The clue the Atomic ammo gave me was they figured out how to get enough pressure at low velocities to cycle the bolt. Obviously you need a heavy bullet for cycling an AR 223. I took apart the cartridge and what I found was they are using 15.6 grains of a fine flattened ball powder. The bullet is 112 grains and the primer looked like a Winchester small rifle primer. The COL is 2.172”.

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The powder in the Atomic load looked very similar to Alliant 2000-MR, so that’s where I started. I located some 112 grain .224 bullets from Outlaw State Bullets LLC. That was the only place I found that manufactured anything over 100 grains. They make a hollow point bullet that will expand at low velocities.

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Outlaw State Bullets recommended a load using IMR 4227 for a cycling AR subsonic round. I was able to get both Alliant 2000-MR and IMR 4227 working. You will need a 1:7 twist barrel at least 16” long with a carbine gas port. The standard Gas Hole Diameter of 0.070” works fine. This is the AR I used with a Mystic X suppressor.

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Here’s the load data that worked for me. Note, you will probably have to tweak the load data to your specific firearm.

Load Data 1:
9.5 grains of IMR 4227
112 grain HP .224 Outlaw State Bullet
CCI 400 primer
COL 2.260”
1050 FPS

Load Data 2:
9.0 grains of Alliant 2000-MR
112 grain HP .224 Outlaw State Bullet
CCI 400 primer
COL 2.260”
1070 FPS

Here’s the grouping of the IMR load from 25 yards. I did a quick 4-shot test to take a look at the accuracy. I suspect this load will produce somewhere around a 1.5 – 2 MOA grouping. Note, you must use a suppressor to get the bolt lock open. You need the extra pressure the suppressor provides. Also, before you test any load shoot it on paper to make sure your rounds are not keyholding without a suppressor. I needed to load these rounds with a COL of 2.260”. Anything less would not stabilize.

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These loads were not particularly quiet suppressed. There is still a lot of gas coming out of the ejection port. The Alliant powder seemed a little quieter than the IMR powder. Your results may vary. Good luck if you test this load data and let me know how it works for you.

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