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Discussion Starter #1
Tell me, is it not choosing the powder that makes the most peak pressure and fills the case while producing lesser muzzle pressure without going over 1000-1050fps that makes it the optimum quiet load?

I see so many loads where people are using 1680, H110 etc that produces 22000psi peak and 2500 muzzle pressure then they talk about all the unburnt powder they find in the receiver.

It seems Trailboss, Clays, V N32C Tin Star and other fast burning powders would be better choices than what many use.
 

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I've used Unique and 2400 with no problems, but yes, I agree that the faster pistol/shotgun powders are a better choice than rifle powders.
 

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I had no issues with 1680 in the BO but I've not tried TB for subsonic loads. I had issues with Trailboss with copper jacketed bullets and reduced loads in 270 and 308 - lots of velocity variation. A cowboy action shooter told me that Trailboss is made for lead cast bullets. He was shooting TB loads over my chrono with excellent mv consistency at around 1500 fps. I was getting 100 fps or more variation trying for reduced loads in that velocity range.
 

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I believe barrel length plays a huge part in which powder is best to get both consistency and being quiet. To me using a rifle powder for a sub load in the 6.8 or larger cased 308 defeats the purpose of having a sub load, kind of like putting a 4 cylinder in a Caddy, which is why my 2 sub calibers are the 300 BO and the 350 Legend. Thus I'm seriously thinking of building a 300 BO around a 6 inch barrel and making it sub only. AA5/9 are the powders I'll begin testing, with Unique as my fall back, hopefully after the summer and CV-19 have passed.
 

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Discussion Starter #6
Agree on barrel length and bullet weight. If I'm looking for a sub load I want it quiet. I'll find the load then make it cycle.
 

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I use Tin Star with 240 gr bullets in my .30HRT and 450 gr lead bullets in the 458 socom.
 

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Subsonic has to do with altitude, humidity, and keeping the velocity for my location, below 1100 FPS. In testing the old school test is if you can hear the bullet hit a paper target at 100. I run a 6.5 Grendel with 160gr in a sub gun full function with H-110, a 358 MGP 250gr and 200 RCBS sub Gun and a 300 BO 220gr sub gun with H-110. The velocities run about 1090. There is a site on the web to look up the speed of sound for your location. My altitude is 247 feet.
The idea is to get as close to super sonic as you can, with the least standard deviation so shot for shot stays below your speed of sound. The can only controls the muzzle blast, not the supersonic crack or bullet impact, whack.
The reason I use H-110 is because: 1. I have a good bit of it and 2. When developing the full function 6.5 I called J.D. and asked him about his development of the Black Out.
 

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Discussion Starter #9
When developing a quiet load I would choose a powder that burns faster and produces 1900psi at the muzzle than a slower burning 1680 that produces 3000psi at the muzzle. That is 33% less pressure/blast at the muzzle. Of course choosing one that is below subsonic and one that is consistent and accurate is a part of choosing the correct powder. I understand carbine length gas systems complicate the function of the rifle using subs. When using 210-220gr bullets some powders can produce 50000psi peak but only have 2000psi at the muzzle. Some slower powders only produce 24000 psi peak but still have 3000psi at the muzzle due to the powder still burning and creating pressure further down the tube. AA9 and Clays is much quieter than 1680 from my testing 10 years ago.

It seems to me most (from reading on forums)are picking a powder that cycles the action not one that is quieter...the reason for shooting subs.
 

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Discussion Starter #10
A good friend sent me a 300 BO 10" faxon barrel to help him work up sub only loads and it isn't for hunting. This thing has a .101 gas port at the pistol location so it is way over-gassed. I used a .101 at the carbine gas location on 16" barrels and they cycled subs and supers. Needless to say the first thing is to get an adjustable gas block on it.
 

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Quick Load really helps here. You want a powder to burn 99% in given brl length. This keeps pressure at the muzzle down. Powders that burn before the bullet exits the bore tend to have wild extreme spread. A cold brl will shoot different than a warm one. My load with a 6" 300blk was with VV N105 & 208 Amax/ELD.
 

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Discussion Starter #12
Yeah I've been using QL since 2007, it gives some decent starting points. Think I'll start with Clays and Tin star.
 

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Grains:190 Hornady SubX 8.0gr Acc#9
Hi Vel: 1091 COAL 2.079 to 2.102
Low Vel: 1084 Ogive 1.585 to 1.596
Ave Vel: 1088
Ext Spread: 7
Std Dev: 3
Less 1/2" 35 yards
Velocity Power Factor Ft/Lbs
1091 207.29 502.117
1084 205.96 495.694
1089 206.91 500.278
Going to try and shorten the COAL and up Pressure


Grains:180 Win-PP Lake City Brass (range pick-ups
Hi Vel:1070
Low Vel:1062
Ave Vel:1066
Ext Spread:8
Std Dev:4
Winchester 180 Power Point (plinking load)
Accurate #9 - 8.4gr (trying to stay subsonic
VelocityPower FactorFt/Lbs
1062191.16450.737
1068192.24455.844
1070192.6457.553
 
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