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Author Topic: Serious Subsonic Cartridges  (Read 10816 times)

Nolo

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Serious Subsonic Cartridges
« on: January 23, 2009, 01:40:18 AM »
I've been giving a lot of thought to subsonic cartridges recently, especially the promising 9x39mm.
Basically, it seems to me that the subsonic rifle cartridges are a lot like regular pistol ball ammo in performance but with extended range and armor-penetrating capability.
I am wondering, basically, what can be done to make a subsonic cartridge as powerful as a rifle? Obviously if you measure just muzzle energy, you'd have to make the bullet massive, about 500 grains or so until you hit 5.56 NATO energies. So, that's probably not a good measurement.
Terminal ballistics are nebulous at best, but my general impression is that subsonic or low supersonic (>2000 fps) pistol ammo really can't approach rifle ammunition for effectiveness on human targets.
What can be done past the normal expanding bullet strategy to make subsonic rifle rounds more powerful?
I am basically just brainstorming the field. Having low-noise or noiseless service rifles would be impressive, and I want to check this avenue out.
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GeorgeHill

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Re: Serious Subsonic Cartridges
« Reply #1 on: January 23, 2009, 01:41:15 AM »
JD Jones beat you to it Nolo.  .300 Whisper.
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Re: Serious Subsonic Cartridges
« Reply #2 on: January 23, 2009, 05:17:14 AM »
Because your speed is limited to less than the speed of sound, the only way to get more energy is to increase the mass of the projectile.

Larger bores tend to be harder to supress, so the idea would be to have heavy projectiles out of something of moderate bore size.

Sounds a bit like a .300 Whisper to me.

Personally I have a little plan to purchase a bubbafied .303 Enfield cheaply (plentiful around these parts) and play around with subsonic loads and a can .... just for fits and giggles.
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Re: Serious Subsonic Cartridges
« Reply #3 on: January 23, 2009, 10:48:26 AM »
I guess you could abrogate the Hague Convention and go to the C. Anvil "XX Special" projectile, with high explosive charge AND dose of poison in case the blast and impact did not kill the opponent.

The BPCR crowd did some work with subsonics, holding the .45-70 down to 1000 fps.  They soon reverted to the traditional 1200fps because test trumped theory and they got better accuracy even with the Mach transition downrange.

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Re: Serious Subsonic Cartridges
« Reply #4 on: January 23, 2009, 11:17:39 AM »
Perhaps a smoothbore weapon?  Less drag = More Velocity.

Obvious issues with accuracy.  Other than that, I'll have to sleep on it.

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Re: Serious Subsonic Cartridges
« Reply #5 on: January 23, 2009, 11:28:46 AM »
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JD Jones beat you to it Nolo.  .300 Whisper.
What does the terminal effectiveness of .300 Whisper (which I am pretty familiar with) look like? I've never seen a study on it? What mechanics does it use to do damage to tissue, etc.?
AFAIK, 9x39mm is designed specifically to penetrate armor. I've heard that it "drops Chechens like a rock", but that's only anecdotes of anecdotes, so it can't be relied upon.
I am not saying .300 Whisper is the right answer, I am just wondering what its terminal ballistics look like.
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Nolo

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Re: Serious Subsonic Cartridges
« Reply #6 on: January 23, 2009, 11:29:24 AM »
Also, doesn't .300 Whisper use bullets designed for supersonic flight? Isn't that a problem?
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Re: Serious Subsonic Cartridges
« Reply #7 on: January 23, 2009, 11:37:19 AM »
Nope.  It's not a problem.  Accuracy is fantastic.  And the down range impact - it hits harder at long range than 5.56mm does.  Higher BC helps a lot.
Nolo - if you want to learn about Ballistics - JDJ is the Yoda.
The best thing about the .300 Whisper is that you can run it in your AR with just a different upper.  You can use your same mags.
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Nolo

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Re: Serious Subsonic Cartridges
« Reply #8 on: January 23, 2009, 11:43:46 AM »
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JD Jones beat you to it Nolo.  .300 Whisper.
I am not sure I enumerated it well in the OP: I am actually not proposing anything new. This is one of those "pick your brains" threads.  ;D :)
I also have no idea what the terminal effectiveness of any of these subsonic rounds is. If it's good (basically better than 5.56), I can choose a round from there (as there are several, as noted). If it's just like a .45 hardball, that's a design problem that I want to tackle.
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Nope.  It's not a problem.  Accuracy is fantastic.  And the down range impact - it hits harder at long range than 5.56mm does.  Higher BC helps a lot.
Nolo - if you want to learn about Ballistics - JDJ is the Yoda.
The best thing about the .300 Whisper is that you can run it in your AR with just a different upper.  You can use your same mags.
Well, accuracy wasn't what I was worried about necessarily. I don't know enough about fluid mechanics, but don't blunt-nosed teardrop shapes have the best BC when they're subsonic?
One of my secret desires is to own an ACR in .300 Whisper.

Mostly, I am worried about terminal ballistics. I know .300 Whisper has been used on hogs with a lot of success, but from what I understand those were mostly supersonic loads a lot like 7.62x39mm.

Like I say, I am not actually proposing anything here. I am trying to figure stuff out. Subsonics is new to me. Thanks for the input, all.
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GeorgeHill

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Re: Serious Subsonic Cartridges
« Reply #9 on: January 23, 2009, 11:55:48 AM »
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I don't know enough about fluid mechanics, but don't blunt-nosed teardrop shapes have the best BC when they're subsonic?
No.  BC is BC weather or not it's above or below the sound barrier.  Drag is Drag.  Blunt nosed bullets do have one advantage... which is why slippery pointy boat tails are not always the best choice.  Tissue disruption. That wider ogive when it hits - disrupts more tissue.  It's not a stabbing cut like a pointy bullet.  It's a blunt force trauma that penetrates. 
Look at the bow of a ship.  Say, a sleek sail boat.  It cuts the water with ease and glides through leaving a wake like an arrow-head.  That wake is the water being pushed away.  So the boat, with its sharp lines, loses less energy, so it needs less energy to move through the water.
Now look at the bow of an Ice Breaker or a Ferry.   Wide and blunt.  Look at the water piling up against the bow.  Look at the wakes.  These ships really have to push a lot of water out of the way.
Air behaves the same way.  Air is essentially, a thin fluid.  It moves the same.   Get a cigarette and blow some smoke.  And pass your hand through it flat and edged and look at how it behaves.   Go out to a lake and take a cannoe paddle.  Run it through the water the same way... flat and on edge and look at how the water moves.  The same. 
Now, as you know... tissue is like fluid too. 
Now with tissue you get other neat things.  Bone shards, tendons, blood, etc. 
The .300 Whisper doesn't depend on shock like the 556 does.  It uses good old fashioned penetration.  Momentum and large permanent wound channels.
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Re: Serious Subsonic Cartridges
« Reply #10 on: January 23, 2009, 12:03:56 PM »
Continuing.
The Whisper can be loaded higher or lower according to need.  And it works very well with a suppressor. 
When a bullet goes super sonic, the shock wave of the sound barrier expands off the very tip of the bullet - even a hair in front of it.
This is why you can shoot in the rain - the rain never touches the bullet.  Because of that shock wave.
As the bullet slows... the shock wave moves back along the length of the bullet till it reaches the rear.  Bullets with lower BC's can get de-stabilized by this and accuracy drops.  It's like hitting a speed bump.  Cleaner BC bullets can pass this without much influence and retain their accuracy.
You can see this easily in .308 where this happens between 800 and 900 yards depending on your load.
This transonic bump can be bigger than people think.
Chuck Yeager did it in a an aircraft that had a very clean BC. 
Others before him tried it in aircraft that had lesser BC - and those attempts resulted in the aircraft literally coming apart in mid air like they hit a brick wall.   In Cockpit footage, you can see the pilots getting shaken as they pass the sound barrier and then the plane smooths out all the sudden.  That was transonic flight and it happens in both directions going through it.
( I went to a private school and studied aerodynamics as coursework.  No, I'm not kidding.)
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Re: Serious Subsonic Cartridges
« Reply #11 on: January 23, 2009, 12:08:24 PM »
http://uk.youtube.com/watch?v=dke2i-xO1uo (The video's owner prevents external embedding)
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Re: Serious Subsonic Cartridges
« Reply #12 on: January 23, 2009, 12:33:11 PM »
Wow.  That was rather impressive and very informative.  All stuff I "kinda" knew, but never really put together.

And then there it is all neatly packaged.  Good stuff.  +1


-T.


EDIT:  And... now I want a .300 Whisper.  Damn it. 
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Re: Serious Subsonic Cartridges
« Reply #13 on: January 23, 2009, 12:42:08 PM »
Much appreciated, George. That was highly informative.
I noticed in a ballistic calculator that I used that the same bullet (.357 250-grain boattail, simulating 9x39mm) going subsonic (1040fps) loses 25% less energy at 500 (or was it 1000? I can't remember) yards over a supersonic (2000 fps) bullet.
This was surprising to me, but it seems to fit with your statement.
Again, thank you.

So now the question becomes, .300 Whisper? 9x39mm? .338 Spectre? Etc, etc.
Thanks for listening

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Re: Serious Subsonic Cartridges
« Reply #14 on: January 23, 2009, 12:43:44 PM »
In case you are wondering... Dangerous Game Bullets - those bullets that you want to kill RIGHT THERE DEAD kinda things - like charging Lions or Elephants.  Those all use rounded blunt bullets, not Spitzers.  There is a reason for that.  And now you know the reason those are all 200 yard or less guns.

You've now taken your first steps into a larger world. /Kenobi
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Re: Serious Subsonic Cartridges
« Reply #15 on: January 23, 2009, 12:57:30 PM »
Nolo - When you are looking at those balistic results... make sure that you factor in heavier bullet weights with the higher BC's.  Heavier means longer, and longer tends to mean higher BC.  But not always.  Such as my Beloved 7mm... which is almost always a higher BC than other calibers unless those other calibers go with very heavy bullets for caliber... ahem... anyways... Look at the Hornady 154 grain SST and compair that to the 162 grain BTSP.  The 154 has a higher BC, even if it is shorter... and the BTSP is pointy... but look the bullet over carefully.  Can you see where the drag is?
Now tell me.  How is the 154 SST slicker?  This is subtlety.  Look carefully.  The difference between the two in BC is slight.  But its there.
This might give it away...
Now look at the 162 A-Max' BC.
I do love that bullet.
But it's useless for hunting. 
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Re: Serious Subsonic Cartridges
« Reply #16 on: January 23, 2009, 01:05:13 PM »
Quote
Nolo - When you are looking at those balistic results... make sure that you factor in heavier bullet weights with the higher BC's.  Heavier means longer, and longer tends to mean higher BC.  But not always.  Such as my Beloved 7mm... which is almost always a higher BC than other calibers unless those other calibers go with very heavy bullets for caliber... ahem... anyways... Look at the Hornady 154 grain SST and compair that to the 162 grain BTSP.  The 154 has a higher BC, even if it is shorter... and the BTSP is pointy... but look the bullet over carefully.  Can you see where the drag is?
Now tell me.  How is the 154 SST slicker?  This is subtlety.  Look carefully.  The difference between the two in BC is slight.  But its there.
This might give it away...
Now look at the 162 A-Max' BC.
I do love that bullet.
But it's useless for hunting. 
I just used a calculator to figure out a certain BC and compare likes.
I wasn't actually designing anything, I was just doing a test.
If at all possible, I try to use real BCs of real bullets in my calculations.

As for the BTSP, is it the nose? Or the sort of corner it has between the ogive and the body?
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JesseL

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Re: Serious Subsonic Cartridges
« Reply #17 on: January 23, 2009, 01:14:19 PM »
Just for the convenience of those of us trying to see what George is talking about:

Hornady 154gr SST, BC .525:

Hornady 162gr BTSP BC .514:
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Re: Serious Subsonic Cartridges
« Reply #18 on: January 23, 2009, 01:21:20 PM »
The secant ogive is important.  Now loot at the positions of the cannelure.
The A-Max doesn't have one.

Disruption is just as important as the shape of the nose.

This is why the Air Force was playing with Bottle Shaped, or Wasp Shaped aircraft fusilages.  Not because of the stuff that they needed to fit under the skin - but how it moved through the air.   This is also why Howard Hughes had his speed planes with "Shaved" Rivets.  Less disruption, less drag.

Speed is Life.  Drag is too.   To retain that down range energy - you want as little drag as possible.  A higher BC.
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Re: Serious Subsonic Cartridges
« Reply #19 on: January 23, 2009, 03:14:26 PM »
Quote
The secant ogive is important.  Now loot at the positions of the cannelure.
The A-Max doesn't have one.

Disruption is just as important as the shape of the nose.

This is why the Air Force was playing with Bottle Shaped, or Wasp Shaped aircraft fusilages.  Not because of the stuff that they needed to fit under the skin - but how it moved through the air.   This is also why Howard Hughes had his speed planes with "Shaved" Rivets.  Less disruption, less drag.

Speed is Life.  Drag is too.   To retain that down range energy - you want as little drag as possible.  A higher BC.
I am assuming the bullet with the more forward cannelure has a higher BC because the cannelure gets caught in the shockwave and doesn't affect performance as much?
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Re: Serious Subsonic Cartridges
« Reply #20 on: January 23, 2009, 09:42:50 PM »
Nolo, you get an A+ in today's lesson.    :clap
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Re: Serious Subsonic Cartridges
« Reply #21 on: January 23, 2009, 10:21:29 PM »
Hahah, my dad has a Doctorate in Aeronautics and Astronautics. I pick up things sometimes.
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Re: Serious Subsonic Cartridges
« Reply #22 on: January 23, 2009, 10:43:12 PM »
The .458 SOCOM can be setup for subsonic operation with 500+ grain bullets, but if you really want quiet, the .338 Spectre is my choice.  The 300 grain SMK is extremely efficient at subsonic velocities and the case forming is no work at all compared to 300 Whisper.  

I've been working on an slightly extended .30 Mauser.  It should work really well in 5.45 magazines, but I haven't had a chance to do much with it.  Likewise I've looked at a .408 cartridge off of .45 Win Mag brass, but haven't gone beyond necking down some brass.  

I can imaging a .40 caliber version of this bullet coming out of a rebarreled .308 Siaga or SR25.

http://lehighbullets.com/proddetail.asp?prod=510%2D210

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Re: Serious Subsonic Cartridges
« Reply #23 on: January 23, 2009, 10:51:33 PM »
See, this page doesn't show any recovered bullets in subsonic ranges, suggesting that they don't perform well terminally under the sound barrier.

I like the idea of a silent rifle, but I don't want it to just put a .308, .338 or .356" hole in my enemy!
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Re: Serious Subsonic Cartridges
« Reply #24 on: January 23, 2009, 10:53:56 PM »
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I like the idea of a silent rifle, but I don't want it to just put a .308, .338 or .356" hole in my enemy!
   ???
That's what bullets do.  If you are wanting massive hydrostatic shock effect, you can only get that from high velocities.  That shock is a direct effect of how fast the moving bullet pushes fluid out of its way. 
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