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Best load data for subsonic 300 Blackout


af220wa

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I'm starting to load 300 blackout and looking for the best bullet weight, powder type/grains for sub sonic suppressed.  I'm running a 9.5" Rainier barrel and an Octaine 45 suppressor if that makes any difference.  Any tips or load data is appreciated.

 

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I just copied AACs recommendation. For now to get started.

 

http://www.advanced-armament.com/assets/images/pdf/manuals/300BLK-AACUpper-MiniBro.pdf

 

11.2 Gr of AA1680 at 2.089" OAL

With leatherhead 220 Gr coated Bullets.

Bolt won't lock back unsuppressed, but in my buddies 8.3" suppressed, it locks back.

I'm 6 months in on my suppressor, so still waiting...

 

 

 

 

 

Sent from my iPhone using Tapatalk

 

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  • 2 weeks later...

I don't have my notes with me, but I think I ran around 8-8.5 gr Lil Gun through my 8.5" SBR running cast coated 240 gr bullets.

 

I started with data from Hodgdon and found what load would cycle my gun unsuppressed, yet still subsonic.  I kept the rounds right at 1000 fps.

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  • 3 years later...
  • 5 weeks later...
On 5/19/2017 at 8:04 PM, yellowfin said:

7.2gr W296 with King Shooters Supply 215gr coated bullets, 2.096 OAL.  Accurate, dirt cheap, and so quiet you hear the brass hitting the ground and bullet hitting the target.

 

have you noticed any deposits from using Roger's better bullets?  not sure if there is an issue using their subsonic bullets and then switching back to supersonic and having lead deposits.

 

thanks.

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  • 4 weeks later...

I don't think any of this is best but here is some trials I just did

 

I had been using 8.0gr lil gun under 220 ELD out of a 8.5 psa barrel. Stayed sub sonic and cycled suppressed and locked open plus stayed sub sonic in a ruger ranch rifle with 16" barrel. I switched to a 8" CMMG barrel because it was lighter and move the suppressor closer to the hand gaurd - looked cooler... With this load/barrel I had some short stroking and the gun did not lock open on empty. I tried bumping up the lil gun load

Lil gun 8" barrel 220gr ELD

8.0gr ave 1045fps

8.2gr ave 1084fps

8.4gr ave 1098fps

Both the 8.2 and 8.4 gr loads went super in the ranch rifle

 

So I went to cabelas and actually found a pound of CFE BLK and tried a few

CFE BLK 8" barrel 220 ELD @ 2.212

9.9gr ave 935fps

10.5gr ave 988fps

11.4gr ave 1063fps

All these loads cycled and locked the bolt open. 

Did not try these in the ranch rifle

 

The CFE BLK loads seemed a little dirtier than lil gun and a little louder, but I assume the sound could have been more bolt velocity vs noise out the silco omega suppressor. I had read others info describing CFE BLK being gassy and why it cycles the AR even at very low velocities. Made me think about loading for open where gas is king. I had read about some guys using VV N105 & N110 for 300BO. Wondered if anyone has tried some of the open gassy powders like AA7 etc? Or have any good info to share here?

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  • 8 months later...

I've spent a fair amount of time developing subsonic loads lately and have a couple to share. Data from a POF 10.5" barrel, 1:7" twist.

 

Both loads are with a 225gr. powder coated cast bullet made with NOE bullet mold TL310-225-RN, lead hardness at 24bhn, sized to 0.310".

 

Most accurate and functional:

10.0gr AA1680, WSPM @ 2.180 OAL - 1,025 fps

 

Most quiet but not functional (w/o lighter springing):

7.5gr AA#9, WSPM @ 2.245 OAL - 1,035 fps

 

 

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  • 4 weeks later...

I tried for a while to load the leatherhead bullets for a 8" upper and I had serious issues with leading up my can. The coating on the bullets would shear off and deposit the lead all over the muzzle break, to the point that I gave up on the project and picked up a single shot blackout to play with. If you are doing this with an octane that is user-serviceable then you can just clean the can like you would a rimfire can and call it good. 

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  • 5 weeks later...

Following up on my last post, I found a pretty accurate and functional load using Viht N120.

 

9.8grs N120 under a .310" sized 225gr powder coated cast bullet, WSPM primer, 2.180" OAL. About 985 fps through a 10.5" 1:7" twist barrel.

 

I also discovered the NOE expander plugs which allow you to both flare the case mouth and set neck tension. I'm using the .313" x.309" plug with .310" diameter projectiles, giving me .001" interference which seems to be a good neck tension. I don't see any setback or pressure signs, indicating the bullet is adequately held, but not too tightly as to create unnecessary pressure.

 

Also, don't seat and crimp in the same die if at all possible with cast bullets, it's really easy to create lead rings or shavings that get stuck in the chamber and screw with accuracy until removed. Neck tension exceeding .002" can also create issues with small lead fragments sticking in your chamber in my experience.

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