300 Blackout Subsonic Powders

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  • outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,501
    I wouldn't dynamic entry with a bolt gun either, but that's what OP has. He doesn't need the extra gas that 1680, Lil gun, H110, etc. generate. In my experience loads that are borderline subsonic in a gas gun will go super in a manual action.
    @mtlcafan79 How much gas would be realized with a bolt gun?
     
    Last edited:

    My Toy

    Ultimate Member
    Jul 31, 2008
    1,172
    Westminster
    Thanks for all of the conscientious replies as usual with MDS. Anytime I ask a question or for advice I always make it a habit to reply. Sorry it took so long but I was busy and wanted to test out some more loads in a gas gun as suggested. So I'm still failing at trying to get subsonic. Here are my results with different loads chronographed at 15' from the muzzle. All loads failed to cycle the rifle ( Windom Weaponry 16" upper on 80% lower - not suppressed) except the 12.0 grs of Hodgdon CFE BLK (go figure it's lighter than the load that wouldn't cycle). It occurs to me that since this rifle is not suppressed ( won't get my can until probably March 2024) that when the can is installed it may create more back pressure to cycle the rifle but at any rate these loads in this rifle are not sub sonic. . Anyway here are my results. Please comment.
    All loads: 190 gr. Hornady Sub-X, CCI-450, Starline 300 B.O. cases fired 2x, Lee Factory Crimp.

    Win 296 - 9.4 grs (vel. 1146); 9.6 grs (vel. 1162)

    Hodgdon Lil'Gun - 8.0 grs (vel. 1085); 8,3 grs (vel. 1129)

    Hodgdon CFE BK - 12.0 grs (vel. 1124); 12.3 grs (vel. 1174)

    IMR 4227 - 10.1 grs (vel. 1122); 10.4 grs (vel. 1156)

    Again would be interested in any comments or suggestions.
     

    Park ranger

    Ultimate Member
    Dec 6, 2015
    2,298
    My 190 grain sub x load is 7.3 of lil gun. It functions my pistol gas system and gives me 975-1000 fps. That’s the window I like. If the SD is too high, running 1050 will have some go super.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,835
    Rockville, MD
    All loads failed to cycle the rifle ( Windom Weaponry 16" upper on 80% lower - not suppressed) except the 12.0 grs of Hodgdon CFE BLK (go figure it's lighter than the load that wouldn't cycle). It occurs to me that since this rifle is not suppressed ( won't get my can until probably March 2024) that when the can is installed it may create more back pressure to cycle the rifle but at any rate these loads in this rifle are not sub sonic.
    OK, so let's talk this through for a second.

    First point: rifles with normal-sized gas ports will generally not cycle subs unsuppressed. This is not unusual, and it is not really a problem unto itself. My AR-300BLK frankenbuild with 8.5" CMMG barrel will not cycle subs without a can (SiCo Hybrid in my case). It is rock solid once you put the can on, and cycles reliably at 950fps with a 200gr coated bullet.

    Second point: gas system matters. Does the Windham have a carbine or a pistol-length gas system? If it's carbine, you might find yourself having trouble even with a suppressor.

    All I'm trying to say here is that sometimes it's a load problem, but sometimes it's a gun problem.
     

    My Toy

    Ultimate Member
    Jul 31, 2008
    1,172
    Westminster
    OK, so let's talk this through for a second.

    First point: rifles with normal-sized gas ports will generally not cycle subs unsuppressed. This is not unusual, and it is not really a problem unto itself. My AR-300BLK frankenbuild with 8.5" CMMG barrel will not cycle subs without a can (SiCo Hybrid in my case). It is rock solid once you put the can on, and cycles reliably at 950fps with a 200gr coated bullet.

    Second point: gas system matters. Does the Windham have a carbine or a pistol-length gas system? If it's carbine, you might find yourself having trouble even with a suppressor.

    All I'm trying to say here is that sometimes it's a load problem, but sometimes it's a gun problem.
    My Windham has a carbine length gas system ( about 7.5").
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,835
    Rockville, MD
    My Windham has a carbine length gas system ( about 7.5").
    It's never going to cycle with subs unsuppressed. Gas pressure is not going to be high enough. You may get lucky with a silencer, you may not. If swapping barrels to something with pistol gas is an option, I'd strongly consider it - or spend the money on a form 1 and go to 10.5" with pistol gas or something.
     

    My Toy

    Ultimate Member
    Jul 31, 2008
    1,172
    Westminster
    It's never going to cycle with subs unsuppressed. Gas pressure is not going to be high enough. You may get lucky with a silencer, you may not. If swapping barrels to something with pistol gas is an option, I'd strongly consider it - or spend the money on a form 1 and go to 10.5" with pistol gas or something.
    Thanks, makes sense.

    On another note just found out the suppressor I purchased (Silencerco OMEGA 300 ) which I probably won't receive until March is in the serial number range for the recall due to apparently faulty welds. Not sure who is in actual possession of it now but Monday I'm going to call Silencer Shop and see how they handle this issue.
     

    85MikeTPI

    Ultimate Member
    Jul 19, 2014
    2,658
    Ceciltucky
    It's never going to cycle with subs unsuppressed. Gas pressure is not going to be high enough. You may get lucky with a silencer, you may not. If swapping barrels to something with pistol gas is an option, I'd strongly consider it - or spend the money on a form 1 and go to 10.5" with pistol gas or something.

    Never say never. I got my carbine gas 300bo to cycle subs with skeletonized BCG and wolff buffer spring and buffer.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,501
    OK, so let's talk this through for a second.

    First point: rifles with normal-sized gas ports will generally not cycle subs unsuppressed. This is not unusual, and it is not really a problem unto itself. My AR-300BLK frankenbuild with 8.5" CMMG barrel will not cycle subs without a can (SiCo Hybrid in my case). It is rock solid once you put the can on, and cycles reliably at 950fps with a 200gr coated bullet...
    Have you given thought to opening the gas port?

    My 10.5(pistol gas) Rainier 300blk Ultramatch would not cycle subs unsuppressed without a can and was spotty with a can, even with the gas block wide open. We opened the gas port and it eats anything and everything. Though one would probably never shoot subs without a can, one would likely shoot subs without a can while developing a new subsonic cartridge.
     

    redsandman6

    Active Member
    Dec 22, 2011
    776
    Dundalk
    i run cfe blk at 12.0 grs with 220 gn berry bullets out of a 10.5 inch barrel ar. i am around 1000 fps. when i get home i will get the exact fps.

    i think with the 190 sub-x and the longer barrel you will have to drop the load to get to sub sonic.

    my ar would cycle down at 11.4 grs of cfe blk. with the 220gn. this was with the can. the accuracy was better at 12.0 for me. i will be getting an Ruger American in 300bo for Christmas from my wife. so i will be working up a load for it soon.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,603
    Pasadena
    Thanks for all of the conscientious replies as usual with MDS. Anytime I ask a question or for advice I always make it a habit to reply. Sorry it took so long but I was busy and wanted to test out some more loads in a gas gun as suggested. So I'm still failing at trying to get subsonic. Here are my results with different loads chronographed at 15' from the muzzle. All loads failed to cycle the rifle ( Windom Weaponry 16" upper on 80% lower - not suppressed) except the 12.0 grs of Hodgdon CFE BLK (go figure it's lighter than the load that wouldn't cycle). It occurs to me that since this rifle is not suppressed ( won't get my can until probably March 2024) that when the can is installed it may create more back pressure to cycle the rifle but at any rate these loads in this rifle are not sub sonic. . Anyway here are my results. Please comment.
    All loads: 190 gr. Hornady Sub-X, CCI-450, Starline 300 B.O. cases fired 2x, Lee Factory Crimp.

    Win 296 - 9.4 grs (vel. 1146); 9.6 grs (vel. 1162)

    Hodgdon Lil'Gun - 8.0 grs (vel. 1085); 8,3 grs (vel. 1129)

    Hodgdon CFE BK - 12.0 grs (vel. 1124); 12.3 grs (vel. 1174)

    IMR 4227 - 10.1 grs (vel. 1122); 10.4 grs (vel. 1156)

    Again would be interested in any comments or suggestions.
    Go with 220gr pills and back down the powder weights.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,603
    Pasadena
    It's never going to cycle with subs unsuppressed. Gas pressure is not going to be high enough. You may get lucky with a silencer, you may not. If swapping barrels to something with pistol gas is an option, I'd strongly consider it - or spend the money on a form 1 and go to 10.5" with pistol gas or something.
    My 10.5" Troy AR cycles with the American Eagle subs and it's quiet with the can on. I've only ever shot subs and they have all worked, but I was not loading the cartridges. It has a pistol length gas tube which probably helps with the gas.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,835
    Rockville, MD
    My 10.5" Troy AR cycles with the American Eagle subs and it's quiet with the can on. I've only ever shot subs and they have all worked, but I was not loading the cartridges. It has a pistol length gas tube which probably helps with the gas.
    Yeah, that is my point... pistol-length gas is the big differentiator here. I run a CMMG 8.5" barrel myself and get reliable cycling below 1000fps as long as I've got a can on there.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,458
    Socialist State of Maryland
    Have you given thought to opening the gas port?

    My 10.5(pistol gas) Rainier 300blk Ultramatch would not cycle subs unsuppressed without a can and was spotty with a can, even with the gas block wide open. We opened the gas port and it eats anything and everything. Though one would probably never shoot subs without a can, one would likely shoot subs without a can while developing a new subsonic cartridge.
    For my 8" pistol, I opened up my gas port to .100 and regulate it with an adjustable gas block. I also use a H3 buffer with a carbine spring and a Palidin 300 suppressor. I think the load I use is 9.5 H110 and 220gn Berry bullets. They stay subs and operate the action with no problem.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,603
    Pasadena
    Yeah, that is my point... pistol-length gas is the big differentiator here. I run a CMMG 8.5" barrel myself and get reliable cycling below 1000fps as long as I've got a can on there.
    So can you shoot without the can if it's like 1050FPS? The ammo I shoot is marketed as 1000fps and has cycled with or without a suppressor. What buffer spring are you running? Mine is a Sprinco blue carbine spring with an H2 buffer.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,835
    Rockville, MD
    So can you shoot without the can if it's like 1050FPS? The ammo I shoot is marketed as 1000fps and has cycled with or without a suppressor. What buffer spring are you running? Mine is a Sprinco blue carbine spring with an H2 buffer.
    My original batch of subs was closer to 1050, and didn't cycle, either. Suppressor backpressure is more substantial than people give it credit for.

    I am running either a carbine buffer or an H1, with a normal carbine spring, and not using adjustable gas. I cannot even imagine why I'd use a heavier buffer and an extra-power spring when I mostly want weak ammo to run. :)
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,603
    Pasadena
    My original batch of subs was closer to 1050, and didn't cycle, either. Suppressor backpressure is more substantial than people give it credit for.

    I am running either a carbine buffer or an H1, with a normal carbine spring, and not using adjustable gas. I cannot even imagine why I'd use a heavier buffer and an extra-power spring when I mostly want weak ammo to run. :)
    I'll have to double check on the spring buffer combo. I have about one of each and I can never remember which lower they are in unless I start having issues. If it runs I don't worry about it.
     

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