Subsonic

[BRDN]

So I’ve been scouring the threads on subsonics for days now. I have more questions than answers now😎
Anyway, it’s my first ar 300 blackout. 10 inch barrel, suppressed. A 150 gr bullet over 6 grains of trail boss is whisper quiet. However, my Lee 230 gr cast PC boolit over 7 gr of lilgun is not! It is subsonic, but no where near as quiet as the 150 gr Will going to a faster powder (similar to tb) get me down to whisper with thee 230 gr boolit?
And, which powder?

Thanks,
Don

[Kestrel4k]

I have found specific chrono numbers useful in suppressed tuning loads for noise; what are you getting with each load ?

[popper]

Lilgun only burns 50% of your powder in a 10" barrel. Way too slow. Try 2400 or unique.

[405grain]

Bullseye, Red Dot, Green Dot, Unique. Use a powder that will finish the combustion inside the barrel.

[charlie b]

Keep in mind I don't own a suppressor. But, I have fired a bunch of subsonic loads from a rifle (and I might have stayed in a Holiday Inn :) ).

The above is good. Faster powder is better. I'd use the fastest powder capable of getting up to speed and still under max. This is where longer barrels are more flexible.

Larger bullets at same vel with same powder will be louder. Takes more overall 'pressure' to get them to the same speed. That extra pressure is like popping a champagne cork. Don't know if this is the same with a suppressor.

Last, are you sure you are subsonic? The transonic zone is 'wide' and atmospheric changes cause a slight difference in the speed of sound, especially temperature and altitude. That and 'book' velocity values are not always what you get in your gun.

[jcren]

All good answers, faster powders burn inside the barrel and have less of a muzzle blast when the bullet exits. I use a lot of red dot for subsonic, but some powders are also quieter than others at a given velocity. Unique and cfe pistol are much lower toned and sound mellower than bullseye or autocomp.

[BRDN]

Thanks for the good advice. I have chronographed them all and so far everything is under 1050 fps. Faster powder it is!!

[BRDN]

Fascinating. Loaded up the 230 gr boolit with 6 gr and 6.5 gr of Universal (closest thing I had to Unique). 970 fps. Very quiet, but very unstable. Boolit tumbles.

[Iron369]

I use 10.8gr of Accurate 1680 under a 220gr lead projectile in a 8.5” suppressed sbr ar15. It’s quiet enough to make me giggle every time.

[popper]

Super vs subsonic bullets make little difference in the bang at the muzzle. Even a subsonic 'load' produces a supersonic gas shock wave at the muzzle -- that is what supressors try to eliminate. Push gas through a hole, smaller hole = higher velocity. The 'hole' is the space around the bullet when it leaves the crown and where an imperfect base causes poor accuracy. Probably has the most effect with bullet damage in the bore second.

[Finster101]

I'm using 9.8 grns of Accurate 1680 with a 7.5 inch barrel and 230 grain boolit in an AR pistol. Very quiet and runs the gun well including locking the bolt back. I have tried several other powders for subs but keep coming back to 1680.

[GhostHawk]

I have shot .357 mag loads with 158 gr bullet over 4.6 grains of Red Dot that were quieter than some .22LR I have shot. No suppressor involved.

They are just plain quiet.

Increasing bullet weight is going to increase pressure which will increase noise.

So I would go back to the 150 gr, pick a fast powder with a moderate charge and see what you get.

Red Dot is amazingly quiet in most of my riles. And it does not need a lot of barrel length to do it in.

My .444marlin Handi rifle actually has a doppler effect like a slide whistle. Starts low and zips high very fast. But no loud crack or snap.

[Finster101]

I did not see it mentioned, is the OP using a suppresser?

[BRDN]

I’m using the powders I have before I buy more..��. I tried Accurate no. 7 today, 10 grns, it shot very well but 1320 fps. Tried 7 and 8 grains of longshot and more tumbles.
Thanks everyone for the advice. Tomorrow I’ll lower the number 7 and try Clays and 2400. If that doesn’t work out I’ll make the drive for the red dot and 1680.
Thanks everyone,
Don

[BRDN]

I did not see it mentioned, is the OP using a suppresser?

Yes

[charlie b]

I’m using the powders I have before I buy more..��. I tried Accurate no. 7 today, 10 grns, it shot very well but 1320 fps. Tried 7 and 8 grains of longshot and more tumbles.
Thanks everyone for the advice. Tomorrow I’ll lower the number 7 and try Clays and 2400. If that doesn’t work out I’ll make the drive for the red dot and 1680.
Thanks everyone,
Don

That's one of the problems with the heavier bullets. You are on the edge of stability so you have to load just below the speed of sound. Just a matter of finding the fastest powder that will get you there without too high a pressure.

The lighter bullets are shorter so they will remain stable at a lower muzzle vel.

[mehavey]

Clays will be near as faster as Red Dot.
It should satisfy your reqm'ts for complete burn before muzzle exit.
Doing it in a 10" barrel.....

But tumbling due to insufficient speed (actually bullet rotation/rpm) will still be a breaking point.
(Running the calcs, though, a 150gr Sierra/common nose design at 1,100fps/10-twist "should" be stable)

[Finster101]

My experience is that most short 300 BO barrels are 1 in 7 or 1 in 8 twist. Stabilization should not be that big a problem.

[BRDN]

Had a great day loading, shooting and learning. The subsonic realm is addictive��. For the 230 gr boolit I used Clays, Trail boss, Universal, no 7, 2400, lil gun and reloader 7. I shot from 600 fps to 1300 fps. In the end the trail boss was the quietest. But I could only get 7.5 gns in the case and it was compressed (850 fps). The clays (7 gr). 1100 fps shot great. Universal wouldn’t stabilize the boolit at any speed. Accurate no 7 tumbled also. Reloader 7 was on a whim, too loud.
In the end the clays, 2400 and lil gun shot the best but I really couldn’t tell any difference in the sound. It’s quiet enough with the suppressor to not need hearing protection but nothing like shooting a 150 gr boolit. I’m going to move down to a 180 gn boolit and see if I can get it to whisper like the 150.
Thanks folks for your help,
Don

[mehavey]

trail boss was the quietest. But I could only get 7.5 gns
in the case and it was compressed (850 fps)
Never compress Trailboss....

[Driver man]

I shoot a 230 grain in a 7.62x39 bolt gun using AP70 (UNIVERSAL) 1000 fps using 6 grains of powder with perfect stability. It needs a good crimp . Very quiet with a sound moderator and quieter than a 22 without.

[truckjohn]

Honestly, questions like this are why Quickload is such a powerful tool. My own experience has been that incomplete burn leads to much of the muzzle blast and even increases perceived recoil. I was amazed at how much more pleasant shooting can be with a significantly reduced muzzle blast, even without a can. When I saw burn data - I realized that many of the "case full of slow burn powder" recipes may see 70-80% burn, and that's why you get the massive "Ka-Whomp" that sounds like a howitzer.

It also makes a huge difference hunting when you're shooting at dawn or dusk, as nearly complete burn reduces muzzle flash considerably.

If it was me, I would shoot for a load that produces nearly 100% burn prior to the suppressor. That means all you need to tame is the hot gas, not a cloud of burning powder grains. As a side benefit, you should get less fouling in the suppressor.

Best of luck on your quest.

[D.Bullets]

My suppressed AR 300 Blk w/8.5in barrel w/cast P.C. 233gr. bullet and a standard bolt took 10.8gr. of A1680 to cycle and lock the bolt back. I purchased a more efficient bolt carrier and that took 8.5gr of A1680 to cycle and lock back with same cast bullet. Thats everything being clean. I settled on a load of 8.8gr of A1680 . Be safe! Always make sure the bullet makes it out of the barrel. Dont ask...

[D.Bullets]

My suppressed AR 300 Blk w/8.5in barrel w/cast P.C. 233gr. bullet and a standard bolt took 10.8gr. of A1680 to cycle and lock the bolt back. I purchased a more efficient bolt carrier group and that took 8.5gr of A1680 to cycle and lock back with same cast bullet. Thats with everything being clean. I settled on a load of 8.8gr of A1680 . Be safe! Always make sure the bullet makes it out of the barrel.

[Iron369]

My suppressed AR 300 Blk w/8.5in barrel w/cast P.C. 233gr. bullet and a standard bolt took 10.8gr. of A1680 to cycle and lock the bolt back. I purchased a more efficient bolt carrier and that took 8.5gr of A1680 to cycle and lock back with same cast bullet. Thats everything being clean. I settled on a load of 8.8gr of A1680 . Be safe! Always make sure the bullet makes it out of the barrel. Dont ask...

What more efficient bolt carrier?

[BRDN]

My suppressed AR 300 Blk w/8.5in barrel w/cast P.C. 233gr. bullet and a standard bolt took 10.8gr. of A1680 to cycle and lock the bolt back. I purchased a more efficient bolt carrier and that took 8.5gr of A1680 to cycle and lock back with same cast bullet. Thats everything being clean. I settled on a load of 8.8gr of A1680 . Be safe! Always make sure the bullet makes it out of the barrel. Dont ask...

Well….I have to ask now!!!��. Just kidding
Thanks

[P Flados]

Subsonic ammo sound levels will generally be lower with lower muzzle pressure. Faster burning powders and less airspace help reduce muzzle pressure.

Here are some Quickload evaluations for different powders as needed to get 1020 fps from a 10" BO. I sorted by muzzle pressure and only included some of the better results.

We will start off with a 150. You did not specify bullet. I used a Lee and seated 0.25" deep (length of the neck).



Cartridge : .300 AAC Blackout (SAAMI)
Bullet : .309, 150, LEE C309-150-F
Cartridge O.A.L. L6: 1.982 inch = 50.34 mm
Barrel Length : 10.0 inch = 254.0 mm

C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Hodgdon Clays 49.1 4.4 0.29 1020 100.0 25069 1968 1.094 25069 1968
IMR TrailBoss 95.1 6.0 0.39 1020 100.0 21867 2012 1.155 21867 2012
Hodgdon TiteGroup 31.0 4.8 0.31 1020 100.0 20766 2064 1.161 20766 2064
Lovex S015 44.0 4.6 0.30 1020 100.0 20296 2084 1.172 20296 2084
Accurate Solo 1000 44.0 4.6 0.30 1020 100.0 20296 2084 1.172 20296 2084
Alliant RED DOT 46.2 4.3 0.28 1020 100.0 20974 2089 1.165 20974 2089
Lovex S011 36.7 4.7 0.30 1020 100.0 18702 2124 1.190 18702 2124
Alliant GREEN DOT 43.5 4.6 0.30 1020 100.0 19449 2133 1.198 19449 2133
Lovex D013 42.9 4.2 0.27 1020 100.0 19425 2140 1.190 19425 2140
Accurate Nitro 100 42.9 4.2 0.27 1020 100.0 19425 2140 1.190 19425 2140
Hodgdon HP38 31.0 4.9 0.32 1020 100.0 18356 2153 1.204 18356 2153
Winchester 231 34.6 4.9 0.32 1020 100.0 18002 2173 1.212 18002 2173
Accurate Solo 1250 43.1 4.8 0.31 1020 100.0 17552 2182 1.220 17552 2182
Lovex D032 28.9 4.6 0.30 1020 100.0 17729 2189 1.214 17729 2189
Hodgdon Universal 38.9 4.7 0.30 1020 100.0 17144 2253 1.253 17144 2253


And here is a Lee 180. Again 0.250" seating depth. Note the first trailboss load shown is compressed at 1020 fps. Probably not a good choice. I re-ran that one powder at 100% fill and added it in with the lower resultant velocity. The Clays load looks pretty good and should let you get a little more speed.



Cartridge : .300 AAC Blackout (SAAMI)
Bullet : .309, 180, LEE C309-180-R
Cartridge O.A.L. L6: 2.127 inch = 54.03 mm
Barrel Length : 10.0 inch = 254.0 mm

C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
IMR TrailBoss 110.5 7.0 0.45 1020 100.0 30089 2300 1.105
IMR TrailBoss 100.0 6.3 0.41 965 100.0 25583 2100 1.187
Hodgdon Clays 57.9 5.2 0.34 1020 100.0 32905 2300 1.065
Hodgdon TiteGroup 36.2 5.5 0.36 1020 100.0 28262 2373 1.114
Lovex S015 51.3 5.3 0.35 1020 100.0 27577 2393 1.123
Accurate Solo 1000 51.3 5.3 0.35 1020 100.0 27577 2393 1.123
Alliant RED DOT 54.0 5.1 0.33 1020 100.0 28297 2407 1.118
Lovex S011 42.5 5.4 0.35 1020 100.0 25755 2413 1.138
Alliant GREEN DOT 50.5 5.3 0.34 1020 100.0 26536 2436 1.142
Hodgdon HP38 35.9 5.7 0.37 1020 100.0 25293 2444 1.149
Lovex D013 49.9 4.9 0.32 1020 100.0 26423 2454 1.138
Accurate Nitro 100 49.9 4.9 0.32 1020 100.0 26423 2454 1.138
Accurate Solo 1250 49.6 5.6 0.36 1020 100.0 24344 2456 1.161
Lovex D032 33.2 5.2 0.34 1020 100.0 24544 2458 1.156
Winchester 231 39.9 5.7 0.37 1020 100.0 24833 2461 1.155
Hodgdon Universal 44.6 5.4 0.35 1020 100.0 23656 2531 1.185

[BRDN]

P Flados!! That is so Cool!! Thank you! That is very informative.
If time ever permits, I would love to see the data on the Lee TL309-230-5R boolit!
Thanks again,
Don

[P Flados]

I looked for the TL309-230-5R but it was not in the QL bullet list. Can you provide actual weight, bullet length & your COAL.

[BRDN]

I looked for the TL309-230-5R but it was not in the QL bullet list. Can you provide actual weight, bullet length & your COAL.

Yes, COAL..2.240. Actual bullet weight. 227 gr. Length….1.36

314041

[BRDN]

I looked for the TL309-230-5R but it was not in the QL bullet list. Can you provide actual weight, bullet length & your COAL.

Yes, COAL..2.240. Actual bullet weight. 227 gr.

314041

[P Flados]

The 230 seating depth came to 0.487" based on your inputs. The reduced case capacity made trailboss not work due to excess compression. Also note that the Clays load looks hotter than recommended for many guns.



Cartridge : .300 AAC Blackout (SAAMI)
Bullet : .309, 200, LEE TL 309-230
Cartridge O.A.L. L6: 2.240 inch = 56.90 mm
Barrel Length : 10.0 inch = 254.0 mm

C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

Powder type Filling/Loading Ratio Charge Charge Vel. Prop.Burnt P max P muzz B_Time
% Grains Gramm fps % psi psi ms
--------------------------------- -----------------------------------------------------------------
Hodgdon Clays 83.9 5.9 0.38 1020 100.0 55454 2417 1.018 !DANGEROUS LOAD-DO NOT USE!
Hodgdon TiteGroup 51.8 6.2 0.40 1020 100.0 49289 2454 1.045 ! Near Maximum !
Hodgdon HP38 51.1 6.3 0.41 1020 100.0 44740 2500 1.066
Alliant RED DOT 77.7 5.7 0.37 1020 100.0 48546 2511 1.050 ! Near Maximum !
Winchester 231 56.7 6.3 0.41 1020 100.0 43991 2513 1.071
Alliant GREEN DOT 72.2 5.9 0.38 1020 100.0 46172 2516 1.061
Accurate Nitro 100 71.4 5.5 0.35 1020 100.0 45864 2549 1.062
Accurate No.2 60.2 5.9 0.38 1020 100.0 38476 2573 1.100
Hodgdon Universal 63.2 6.0 0.39 1020 100.0 41702 2576 1.088
Winchester WAP 50.6 6.5 0.42 1020 100.0 35390 2681 1.125
Alliant UNIQUE 61.7 5.8 0.38 1020 100.0 36096 2686 1.126
Alliant BULLSEYE 55.0 5.4 0.35 1020 100.0 36469 2704 1.116

[BRDN]

Thanks again P Flados!!! This is extremely helpful!! I can’t thank you enough.
Don

[truckjohn]

I would be sorely tempted to roll some of those Bullseye and Unique loads. My only question is if it would cycle the action properly.

[Finster101]

I would be sorely tempted to roll some of those Bullseye and Unique loads. My only question is if it would cycle the action properly.

Which is why I use 1680.

[mehavey]

I'd suggest Norma 200, or RL-7 (close 2nd)
See https://castboolits.gunloads.com/showthread.php?387647-350-Legend-and-Cast-Boolits&p=4967562&viewfull=1#post4967562
(Similar challenge)

[1006]

I do not have a suppressor and shoot a 150 grain bullet from a 16inch 300BLK AR-loaded as a single shot. So far, I have found Red Dot to be the absolute quietest; Clays is the most accurate. I only test them to 50 yards.

Here are the loads that have worked for me:
314068

[BRDN]

Looking at the quick load data is fascinating! I never considered “MUZZLE PSI”. What’s even more interesting is that muzzle psi and chamber psi don’t necessarily correlate.
You folks have been a ton of help.!!
Thanks again,
Don

[Pmc]

In general for the quietest loads - Keep your velocity below .94 of the speed of sound, use the fastest burning powder you can. Also note the speed of sound can vary based on temperature, altitude and humidity. Shooting in Florida in the summer is different than Colorado in winter. Plan accordingly.

[BRDN]

So… now I need another mold. Between 150-180, no gas check (preferably)that will load in an ar300 blk. I have the Lee 150 fp but it won’t cycle with the flat nose.

Don

[Iowa Fox]

This is a great thread! Thanks to everyone for sharing their hard learned data, I can't imagine shooting without being a caster and reloader.

[P Flados]

So… now I need another mold. Between 150-180, no gas check (preferably)that will load in an ar300 blk. I have the Lee 150 fp but it won’t cycle with the flat nose.

Don

There are two Lee molds that are rather popular in the 300 BO. One is 155 gr one is 160 gr (I have the 160). They were originally intended for 7.62 x 39 and feed pretty good.

Both are gas check. I found that the AR platform seems to deserve a gas check for a "non-typical" reason. I have had several ARs get a lot of lead residue buildup in the bolt / bolt carrier when shooting plain base. I am convinced that as bullet passed the gas port, pressure was still high enough for "gas cutting" through my PC and into the lead underneath. This is probably caused or contributed to the very high flyer rate I got on many of my 300 BO cast bullet loads.

[BRDN]

That makes me feel better P Flados.. I ordered the 160 this afternoon. Kinda figured putting on GC wasn’t that big of a deal.

[BRDN]

Thought I would post this for future readers. I tried various powders from Clays to Reloader 7. The 10 inch barrel was just not quiet enough for me compared to the 16 inch carbine. But, the 16 inch carbine didn’t won’t to cycle. After some research I bought/installed another 16 inch barrel with a pistol length gas system. This combination has worked beautifully!! I followed the advice of the folks in this thread and settled on the A1680 powder. 8 grns with the Lee 228 boolit will cycle and lock. It’s very quiet at 750 fps. 9 grns/955 fps and 10 grns/1022 fps.
Thanks for everybody’s help .
Don