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Discussion Starter · #1 ·
I am currently working on a subsonic load for a 300 blackout. AR platform, 8" Wilson Combat barrel, standard gas port size and gas block, obviously pistol lenght gas system, 1-7" twist. I am attempting to work up loads using 150gr. Hornady fmj-bt, since they are relatively inexpensive. These will be plinking rounds only. I have been using IMR-4227, which shot fairly well, functioned well (with Silencerco Hybrid 46), but I was getting a good amount of unburned powder in the receiver/bolt. I have Lil' Gun and Accurate 1680 on hand, and will start working from the minimum advertised charge and go down in .5 gr increments. If anyone has a similar load/experience with this setup or end goal, please give me some direction. Thanks!
 

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I use 1680 for subs in 300bo, but i use a 220gr bullet. I am not sure how it would work with the 150's, but maybe it will work. I would do all of your load development without the can attached and when you reach a consistent 1050 fps and are sure that the bullets are not keyholeing, then you can put your can back on.

I have a 10" AR and I was quite disappointed with how loud even the subs are. It is just difficult to get an AR platform quiet. The single shot break action or bolt action are much quieter.
 

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Discussion Starter · #4 ·
I use 1680 for subs in 300bo, but i use a 220gr bullet. I am not sure how it would work with the 150's, but maybe it will work. I would do all of your load development without the can attached and when you reach a consistent 1050 fps and are sure that the bullets are not keyholeing, then you can put your can back on.

I have a 10" AR and I was quite disappointed with how loud even the subs are. It is just difficult to get an AR platform quiet. The single shot break action or bolt action are much quieter.
I have read a lot of people stating that the 1680 is loud, particularly in the AR platform
 

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Hodgdon Trail Boss may be just the right choise:

Text Font Line Screenshot Web page


You can start with the described load from Hodgdon and work up to 1050fps.
I have done so in 308Winchester and also 223REM, worked just fine. But I did not try all the way down to Sub velocity in these.

Description from IMR/Hodgdon can be found online, as a PDF file:

Hodgdon Powder Company IMR® TRAIL BOSS® REDUCED LOADS FOR RIFLE AND PISTOL

Many say: Do NOT Compress Trail Boss powder ! It is dangerous.
 

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Somehow I can't post a link to the Hodgdon PDF yet, but you can search online and find it.

The PDF describes how to start with a suitable load for your pistol/rifle cartridge.

You can go to the Hodgdon website, under Products > Smokeless Powder, scroll down to Trail Boss.
And there you can choose either pistol or rifle, cartridge and the bullet weight, and you will see what charge to start with.
Usually there is a max and min charge displayed.
 

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With subs, don’t work UP. Start well above subsonic and work down to 1050 with a chronograph. If you don’t have a chronograph, then this is not something to play with until you do.
 

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Discussion Starter · #11 ·
Update. I ended up using Lil' Gun powder, for my sub loads with the hornady 150gr fmj/bt. I managed to get MOA accuracy, and consistent speeds of 1,050fps with 8.5gr., Winchester brass, Remington 7½ primers,and base to give length of 1.500".
Also, if anyone is interested, I found a hunting load with Hornady 125gr SST, using 19.1gr of IMR-4227, Win brass, and Remington 7½ primers, gives very consistent speeds of 1,980fps, and single digit SD. This is a compressed load, and over Hornady published maximum, so if you use it, start low and work up to it.
Thanks again for all the suggestions!
 

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Update. I ended up using Lil' Gun powder, for my sub loads with the hornady 150gr fmj/bt. I managed to get MOA accuracy, and consistent speeds of 1,050fps with 8.5gr., Winchester brass, Remington 7½ primers,and base to give length of 1.500".
Also, if anyone is interested, I found a hunting load with Hornady 125gr SST, using 19.1gr of IMR-4227, Win brass, and Remington 7½ primers, gives very consistent speeds of 1,980fps, and single digit SD. This is a compressed load, and over Hornady published maximum, so if you use it, start low and work up to it.
Thanks again for all the suggestions!
Hey savage hunter I've been post hunting for weeks finally found your post but have a few extra questions. I have a ruger AR556 10.5 barrel 300blk with adjustable gas block and I also have "lil gun" powder and I've looked all over for the 150gr subsonic ammo with lil gun is there anyway you can help me with what grains of powder I need to be safe shooting 150gr bullets subsonic with lil gun powder I have cci br primers, hornady brass, 150gr fmjbt bullets, hodgdon lil gun powder. If you could get me close to 900 to 950 fps without using a filler. And oal. Or can u give me the recipe you wrote up on here about your experience with lil gun and 150gr fmjbt?
 

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Sub rounds are quite finicky and need to be worked up for the individual barrel/gun. With a sub load, you need to ensure the bullet is stable before you attach your suppressor and you need to do all velocity up without the suppressor attached.

With subsonic rounds, you need to start supersonic and work down to the desired velocity with a chrono. You should not start low with sub rounds as you can stick a bullet in the barrel causing a catastrophe when the next round is fired. This is the opposite of working up a super sonic round.
 
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