Subsonic 300 Blackout loads
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243winxb
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http://www.ar15.com/forums/t_6_42/4...NLY___all_other_comments_will_be_removed.html www.ar15.com You may need to register.
redbullitt
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Lots of info around now! AA1680 does a good job on the 200g or heavier projectiles. Are you shooting a semi auto or a bolt/break gun?
oldpapps
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http://www.300blktalk.com/forum/viewforum.php?f=141&sid=a44dcc041f48cda336b1a5a85275e76a
Look at the bottom 'stickie'.
Look at the bottom 'stickie'.
berettaprofessor
Member
10 grains of 4227 behind a Hornady 208 A-Max, OAL 2.250. Cycles my AR, supposed to be subsonic (it's Hodgdon data), haven't chrony'ed myself yet.
berettaprofessor
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I stand corrected. Chrony today averaged 1138fps. Yeah it was cold, but still a little fast. 60% of rounds were supersonic, if just barely. That's out of a 18" barrel. Hodgdon says it should be 1073fps
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Grumulkin
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I tried several powders for my 300 BLK with 220 grain bullets including IMR 4227. All gave satisfactory accuracy but only 1680 cycled reliably with subsonic loads in my rifle.
Subsonic, but at what temperature?
It makes a diffrence.
from one of my mentors posts on it. (RIP)
_-------------------------------------------
Subsonic is a little stickier proposition. At least in my experience. For starters what is REALLY the sonic threshold? Sure, there are some "standard" answers. But reality is that in practical application they are most often wrong. At least for me, it is pretty depressing to load a batch of subs and go shoot them only to hear that unmistakable "crack" as they go supersonic over the chronograph which says they SHOULD BE subsonic. And pretty frustrating to think that I have learned from that, go make a batch with a little less powder and find it will not fully cycle the bolt.
Trust me, thats frustrating.
Soooooooooooo, this experience sent me on a quest to learn what was going on with that speed of sound thing. To that end I learned something . .
1) Altitude really doesn't have any influence with the speed of sound. Temperature does.
2) There is a really handy online calculator that does all the math for you!!!
http://www.sengpielaudio.com/calculator-speedsound.htm
-----------------------------------
It makes a diffrence.
from one of my mentors posts on it. (RIP)
_-------------------------------------------
Subsonic is a little stickier proposition. At least in my experience. For starters what is REALLY the sonic threshold? Sure, there are some "standard" answers. But reality is that in practical application they are most often wrong. At least for me, it is pretty depressing to load a batch of subs and go shoot them only to hear that unmistakable "crack" as they go supersonic over the chronograph which says they SHOULD BE subsonic. And pretty frustrating to think that I have learned from that, go make a batch with a little less powder and find it will not fully cycle the bolt.
Trust me, thats frustrating.
Soooooooooooo, this experience sent me on a quest to learn what was going on with that speed of sound thing. To that end I learned something . .
1) Altitude really doesn't have any influence with the speed of sound. Temperature does.
2) There is a really handy online calculator that does all the math for you!!!
http://www.sengpielaudio.com/calculator-speedsound.htm
-----------------------------------
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