300 aac blackout question

[wvsturgeon]

I am new to reloading the 300 AAC blackout.
My gun is a 10 inch barrel, 1:7 twist. I have CFE BLK and IMR 4198 powders but ended up getting Hornady SST 180 grain bullets-perhaps these were not the best to achieve subsonic loads?

Now that I have them, I would like to use such but I do not see that particular brand in the Hodgdon 2021 reloading manual. Instead for the Hodgon is the 180 gr SPR SP-can I use the data from the Speer SP bullets for the Hornady SST 180 grain bullets that I have? I saw on line where the 180 grain SST Hornady was used using Lil'Gun powder, which I do not have. Instead, I have IMR4198 and CFE BLK powders. I do not want to compromise safety.

Thanks for your help.

 

[dellet]

The 180 SST will work fine for target shooting. For hunting, unless you get real lucky and it tumbles, it will just pencil through.

Hornady has data, maybe not subsonic, but down to 1200 fps. That would be a good starting point to work down from. It will be close any way due the shorter barrel. They list a COL of 2.210”. I have not seen their latest manual, there might be better data for subs in it.

Sierra has 180 weight class subsonic data.

https://sierrabullets.files.wordpress.com/2017/12/300-aac-blackout-03052018.pdf

If you compare bullet length and calculate seated depth the loads will work. Just make sure that the bullet does not hit the lands.

JBM - Bullet Length List

www.jbmballistics.com

CFE will be easier to work with, but with low case capacity will likely throw some high ES numbers. 4198, may take some work to get reliable cycling, assuming it’s an AR.

Either powder should be very safe to work with, just start high and work down the load to keep from sticking a bullet in the barrel. Use mid range data to start.

This also helps with an AR and wasted components. If it’s won’t cycle with the chosen combination at 1300 fps. It’s not likely to at at 1000 fps.

 

[wvsturgeon]

Dellet,
Sounds reasonable. The blackout is a semi.
Based on the Sierra reload data, will use the Hornady 180 gr SST bullets with14.4 grain of IMR 4198 (1400 ft/sec) and separately CFE BLK 16.4 grain-both seem midrange
Appreciate the advice

 

[dellet]

Should have taken a quick look at the Sierra data, there’s a huge step, 300 FPS from subsonic to low velocity supers.
To save powder I would bump the sub load up 1 grain. Remember those are not safety/pressure limits unless It’s in green for max. It’s an artificial velocity limit.

Hornady data will not have that gap. Sorry about that.

 

[wvsturgeon]

I see what you are saying. Will then stay mid-range, it won't be subsonic but low velocity super
Thanks