In a thread on really heavy-for-case bullets in the 7.62x39 case, subsonic expressed a desire to discuss the subject of subsonic loads and shooting of subsonic loads. (With a "stage name" of subsonic, whoodathunkit? :) )

Personally, I doubt there is sufficient interest here at THL to support much of a 'discussion' on that topic. Nonetheless, I thought I'd start a new thread and open the discussion up for ANY topic that is "esoteric" or "wild-haired" if you will. I'll start the the discussion off focused on "subsonic" loads and shooting, but there's more to the subsonic topic than just shooting slow. I expect those 'other' elements of subsonic shooting will lead us down a variety of rabbit trails. Since I'm starting the thread, I'll state up front that it'll be OK to 'chase those rabbits'. Hopefully, some of our friends from the British Isles will chime in, as suppressors ("silencers") are encouraged in most european countries. (Something that REALLY chaps my rear regarding the US's legal attitude to supressors.)

So...

As most folks that shoot subsonic loads find out pretty quick, barrel twist rate becomes a very important consideration when selecting a projectile. Furthermore, bullet construction becomes a critical issue as well, not just for the hunter that wants a particular kind of terminal performance, but also the paper shooter that seeks a certain external (after internal and before terminal) performance.

Case selection is a BIG issue as well. If one wants to focus on shooting subsonic, it's best to start from scratch and build your firearm from the ground up with your eye consisitently on the subsonic issues. However, that is rarely the case for those that are curious and just starting out. Most want to 'test the water' first before they dive in.

A good place to start looking at what's available in supressed arms and ammo can be found here: http://www.sskindustries.com/index.htm

The best places I know of to start reading about subsonic loads is here: http://guns.connect.fi/gow/QA5.html

I would recommend wandering through both sites. I would recommend avoiding the balderdash that abounds at "tactical" and law enforcement sites.

As for me, I played around at both ends of the speed spectrum - subsonic, and really, really fast sabot'd bullets. In the end, as fundamentally a Hunter, I found both ends to be dis-satisfying in the amount of "fiddling" one had to do in the field. Fiddling around at the bench, I find very entertaining, but ultimately, if I can't Hunt with it, I lose interest in it. That said, I find the "slow" end more interesting than the "fast" end.

My serious efforts with subsonic projectiles used the 7.62x54R, the .308 Win., and the .22RF with the Aguila SSS (Sniper SubSonic). I have toyed with the 7mm BR-based .338 Whisper. Actually, I used a .308 Win case that I shaped into the Whisper. It ends up the same as the case based on the 7mm BR except for flash-hole and web dimensions. I am interested in the .338 Whisper on the .221 Rem Fireball case, but I don't have a rifle with the .223 head to fiddle with.

As you can see at SSK's site, some pretty amazing groups can be shot with the .338 Whisper and a 300 grain bullet. HOWEVER, it doesn't make a great big game cartridge, as the bullets necessary for good ballistics are very poor for terminal performance at low velocities.

And there's the rub.

I have found it practically impossible to fabricate a subsonic big game cartridge. I guess I haven't given up, ('cause subsonics are fun :) )but I have been pretty well thwarted at every turn so far explored. There just are no free lunches.

Don't misunderstand me.

One can definitely hunt big game with subsonic cartridges. However, ranges are on the long archery scale. (One of the biggest caribou I have ever taken I took with a bow at a measured 87 paces.) Given that, I prefer archery.

Subsonic, why don't you post some of the sites you have relied on for subsonic load development and education?

Paul

I'm no expert by any means, and haven't experimented with those kinds of loads enough to really say much on the matter, other than to say, for me, the trouble comes mostly from partially filled cases being sensative to powder orientation.
 
For example, that 10gr Trailboss load fills a .308 about half way. I think this is probably the best load for a .308 subsonic with standard cases (there are special reduced capacity cases that are way too expensive and short lived for me....). By tipping the case forward before firing(powder away from primer), velocity drops below 990fps. Tipping it back (powder against primer) gets me almost 1100fps.
 
Most of my info has come from googling and finding posts on suppressor websites. Hodgdon lists 2 loads on their website for .308 subsonic loads with 168gr SMKs using titegroup and clays.
 
Other than that, the website already posted and SSKs have been about it.
 
For supersonic, but still reduced loads, H4895 works with 60% of the max charge by weight in most rifle cases that have data listed for it (this is their "youth load" suggestion). Varget looks promising for that too, but I have not tried it or heard much about it other than on cast bullet sites.
 
I am pretty interested in finding out if a BTHP really flys better than a RN at subsonic speeds.

Quote[/SIZE]
I am pretty interested in finding out if a BTHP really flys better than a rn.

I'm afraid I'm not going to be much help on that one, as I have always looked down my nose at round-nosed bullets regardless of velocity, and therefore have never used them, even for subsonic loads.[/SIZE]


That said, of late I've been considering a pure cylinder in a couple of my big bored rifles. Once I came to grips psychologically with the fact that the range for subsonic hunting was going to be short, say 100 yds or so, aerodynamic characteristics became secondary, and nothing hit's "harder" than a truly flat nose. There's no flatter nose than that of a cylinder.


This brings up one of those rabbit trails that I referred to. One subsonic author I've recently read marveled at the fact that bullets that tumbled in flight still "magically" maintained their "accuracy". There's no "magic" to it whatsoever. The path a projectile takes is actually the path of it's Center of Mass (CoM). As a projectile tumbles, it tumbles around its CoM. It violates the laws of physics for the CoM to "move around" without an external force (like wind) acting on it. So... There's really no reason - other than psychological discomfort - to complain about key-holing in short-range, low velocity (subsonic), projectiles. In fact, it could be argued that a bullet hitting sideways hits "harder" that one that hits point-on. Especially if it's an FMJ or a sharp-pointed spitzer.


I was wrestling with this with the Aguila SSS in all of the .22s I shot it in (about 8 if I remember correctly). I know of NO .22 RF rifles that have factory twist rates of less than 1:16 (or more than that either). I simply couldn't stabilize that 60-grain SSS in a 1:16 barrel. However, many people reported that they could. It took me a while to reconcile what I was experienceing first-hand, and what was reported to me by reputable sources. My conclusion is that I shoot in significantly colder air than those that can stabilize that bullet in factory 1:16 barrels. The colder the air, the denser it is. The denser the air is, the higher the twist rate required to stabilize a given projectile.


Anyway, when I first started shooting the SSSs, I was getting complete key-holing at ranges as short as 10 yards. However, the precision wasn't bad. Considering that meant that those 60-grainers were hitting sideways, AND like a 'ton 'o bricks', I wrestled with living with the key-holing. I really couldn't "live" with it though. It 'bothered' me. So... I spent $150 (on sale) for a Volquartsen 1:10 barrel for my Ruger 10/22. It shoots like a house-afire and makes little .22 caliber holes in the paper. I 'feel' better now.


I took this rifle with the 1:10 barrel and the SSSs on my first Colorado elk hunt with Hunterbug, with the sole intent of shooting bunnies with it. And I did. That 60-grain .22 bullet, doing about 980 f/s from that barrel, absolutely WHACKS a sheet of half-inch plywood at 50 paces. Goes through it not like a hot knife through butter, but rather like a brick. I expected it to flatten the snowshoes and jackrabbits. It didn't. In fact, I have had much better performance from high velocity .22 rounds than I did with the SSS. The reason is that while it killed 'em sure enough, unless hit in the head, they ALWAYS wandered off a bit before dieing. Conversely, when hit with a high velocity .22 in the body, they seem to take it much "harder" :). It's not mysterious. The 60-grainer simply plows on through providing no shock-derived "anchor". Maybe if the SSS key-holed, it'd 'anchor' them. So... I have relegated the SSS to "large" small game like coyotes and foxes - even wolves maybe. It's a 'thumper' for sure, but in my opinion, it's just not the best bullet for small critters like rabbits and squirrels unless head-shots are the order-of-the-day.


It is my opinion that the wascally wabbits example is an excellent harbinger of what performance would be with subsonic projectiles on big game, unless hit in the head. And I really don't like chasing wounded animals... big or small. I'm thinking that maybe a cylinder would be a more effective "anchor". I make that speculation based on a theory I have about the "work" (in the physics sense) that a bullet does. You can read about that here: http://www.thehunterslife.com/forums/showthread.php?t=566



Paul

From what I have read and seen, if your meplat is small or rounded, you NEED velocity for terminal performance, conversely, if your meplat is large and flat..... velocity is less important.
 
I think a good choice would be a .452" WFN of 360gr or more.....

Quote from: subsonic;91543From what I have read and seen, if your meplat is small or rounded, you NEED velocity for terminal performance, conversely, if your meplat is large and flat..... velocity is less important. That seems a reasonable position to take.

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Quote from: subsonic;91543[/SIZE]

I think a good choice would be a .452" WFN of 360gr or more.....

I assume you mean for hunting.[/SIZE]

I've given the subsonic hunting projectile some considerable thought, and in the end, I keep coming back to the cylinder. Mind you, I haven't yet actually tried a cylinder, so theory and practice may not jibe. And of course a cylinder is a poor "nose" for auto or bolt feeding. I'll come back and address that issue.

Once one acknowledges that aerodynamic efficiency is not the most important factor when considering a subsonic hunting projectile, precision (most use the word "accuracy") becomes the driving factor.

Second to precision is terminal performance - some call this "lethality".

Giving up muzzle velocity for "quiet" renders the "long, pointy" projectile fundamentally unstable. This is because of the relationship between Center of Mass relative to Center of Form. In a long, pointy projectile, the CoM and the CoF are not coincident. In a projectile with pointy end in the direction of travel, the CoM is rearward of the CoF, and this is fundamentally unstable. To overcome this inherent instability, we spin the projectile. The slower the velocity, the faster the twist rate of the rifling must be in order to generate sufficient revolutions per unit time (usually revolutions per minute (RPMs)). In other words, a bullet of a specific design needs to spin at a certain speed in order to be gyroscopically stabilized. Velocity is NOT the issue EXCEPT that it, along with twist rate determines the projectile's rotation. For example...

Let's say that a barrel has a rifling twist rate of 1 rotation in 12 inches of barrel. Let's say the projectile in question needs a minimum rate of rotation of 180,000 revolutions per minute (RPMs). In order to reach that figure for the RPMs, the projectile will have to move down the bore of the barrel at a velocity of 3000 f/s.

MV = RPMs / ((inches per foot/twist rate in inches)*seconds per minute),

3000 = 180,000 / ((12/12) * 60)

Now lets say the twist rate was increased to 1:9. The minimum muzzle velocity necessary for gyroscopic stabilization would then go down to 2250 f/s.

2250 = 180,000 /((12/9) * 60)

The point is, RPMs needed for gyroscopic stability is the driving variable, not MV or twist rate, even though both are part of the calculation.

OK... Now, since we've sacrificed MV for "quiet", we've taken on some challenges with respect to (wrt) in-flight stability. The "long and pointy" projectile is a problem. If one "end" of a mathematical question is "bad", it's easy to go to the other "end" and see if that is any better. In our case, if "long and pointy" is "bad", then we should look at the opposite of "long and pointy", which is "short and not pointy". Discounting a cylinder with length less than one caliber, the shortest, and "not pointiest" projectile available in ANY caliber is the sphere. And voila', the CoM and the CoF are coincident in the sphere. Therfore, we can assume that the sphere is the most stabile projectile in flight. In fact, mathematically speaking, we can say that there is no need for rifling when shooting a sphere, because the mathematically calculated twist rate is infinity - or "smoothbore".

At this point, I'd bet some muzzle loaders are about to rear their heads and say whoa! Roundballs definitely shoot more precisely from rifled barrels. My response is: You're right, but... stablity, especially mathematical stability isn't necessarily associated with precision shooting. The fact is that the sphere IS gyroscopically stable whether it is "wobbling" around or not.

When a sphere is shot from a smoothbore, it rarely (I am told) produces as small a group (precision) as it does when shot from a rifled bore. The reason is that it acts like the 'knuckleball' of baseball. As it moves downrange, it moves left and right and up and down almost randomly. That movement is NOT a function of gyroscopic instability, it is a fuction of random air resistance at the leading edge of the sphere. It is akin to wind moving a "long, pointy" bullet around. Wind doesn't effect the gyroscopic stability of a "long pointy" bullet, but it does effect it's precision. Ditto for the sphere.

So... how do we lose the "knuckleball" effect without renewing the gyroscopic stability "issue"? We spin it. "Whaaat?" you say. "I thought we didn't need any rifling for gyroscopic stability in a sphere." Correct. However, spinning doesn't just provide gyroscopic stability. It also adds angular momentum to the object. In the case of the sphere, the angular momentum generated by spinning, helps it overcome the "knuckleball" effect. Nonetheless, the sphere is only the most gyroscopically stable projectile, not the "best" one.

Going back to the math, we move away from the "long pointy" end, and away from the "short and not pointy" (sphere) end, and pick the least of two evils (often referred to as the "optimum"). Unfortunately, mathematically speaking, there's a lot of ground between "long and pointy" and "short and not pointy".

Every time I look for the least of the two evils of "long and pointy" and "short and not pointy", I get to a cylinder. A short, "squatty" cylinder. Let's look at a cylinder focusing on CoM relative to CoF. When viewed laterally, the CoM of a cylinder will fall exactly on the center-line of a cylinder. Furthermore, it will fall exactly in the longitudinal center of the cylinder. That means that the CoM and the CoF will be coincident - just as it was for the sphere. That is "good" for gyroscopic stability.

What is bad for stability is the flat nose. The flat nose is worse than the forward part of round ball when it come to being effected by air movement. In other words, as the projectile moves down range, it will get pushed around because the air is not streaming evenly around the square nose. (No laminar flow.) However, if we spin the cylinder, then the angular momentum resists the force of the non-laminar flow around the nose. Up to a point, the greater the spin, the better the cylinder bucks the wind.

However, we can round the nose (and butt) of the cylinder somewhat and still keep the CoM and CoF coincident, and help the in-flight stability, (precision), dramatically. At least on paper. :)

So... I finally return to the point at hand, which is: What is the "best" hunting projectile shape for subsonic loads? In my opinion, a double ended truncated cone with rounded edges.


Actually, that's only sorta true. As a matter of fact, I have been working on some radical new bullet designs just for subsonic firearms use. (As well as some for really supersonic use too.)Unfortunately I cannot divulge their designs here. My business partners and I are in the patent process even as I write this, and they could (and would) truly have thier way with me legally, (as well as being seriously P.O.'d), if I divulged these proprietary designs.

So... The double-ended truncated cone, with about a 6-dgree draft on the angle of the cone, with rounded edges, is a pretty good place to start in my opinon. It should have a bearing surface of no more than 1 caliber and each truncated-cone-end should not be longer than half a caliber. (Trying to be a sphere without actually being one.) Such a bullet should hit like a "hammer", and give up as little as possible to gyroscopic stability constraints.


I'll be back with the numbers for taking a .308 caliber bore, and building the above kind of subsonic bullet.

Paul

OK... Here are some things to consider...

First the projectile. See below. It weighs about 115 grains if made of pure lead. It should have a BC of about .189.

Paul

Here's the trajectory...

Paul

And here are the theoretical stability numbers.

Paul

Here's what I note:

1) In the context of CoM and CoF postional relationship, this is pretty good. It would be difficult to make it want to swap ends or "wobble".

2) The trajectory is so-so - 24" low at 150 yds. I am pretty uncomfortable with any greater hold-over when hunting. And remember, that would be hold over the head, not the body. Meaning... it's easier to hold 24" over the heart than it is over the head because you have the back for reference when holding over the heart.

Also note the impact energy at 150 yds - ~200 ft-lbs. That's about the muzzle energy of the .22 caliber, 60-grain SSS. I wouldn't want to take on a moose (head shot) with anything less than that.

3) Stability-wise, this projectile should be very stable down to essentially any practical MV.

4) I would expect that it would be easy to get excellent precision from this projectile.

Paul

So we're talking about lead wadcutters here? On a different note, there is a lot to be gleaned from looking at the Black Powder Cartridge Rifle (BPCR)  end of the shooting sports. Even the 45-110s and 50-90s seldom exceed 1375 f/s. The speed of sound at sea level, standard humidity and 59 degree Fahrenheit is around 1150 f/s (metric equivalents to be provided later for our international brethren). The problem with some rounds (including .22 rimfires) is that they get buffeted by shockwave turbulence as they transition from supersonic to subsonic. Those 550-650 grain hunks that get thrown aren't as perturbed by virtue of their mass. You'll find that most .22 rimfire target loads are subsonic to avoid that transonic buffeting.

A very interesting link you'll want to check out is www.corbins.com. They make industrial precision bullet making equipment but there's a lot of interesting information there. http://www.corbins.com/subsonic.htm has a great article that might help with subsonic hunting loads.

Thanks for the mention of Corbin's place. I had forgotten that he posted a subsonic page.

The trans-sonic boundary "buffeting" is also why long-range (> 600 yds) target shooters strive to keep their bullets supersonic well past the target distance. Not always easy with the .308 Win case, a 180-grain+ bullet, and a 1000 yd target.

WRT the BPCR arms, I agree in large part. Still supersoninc is not subsonic. In other words, 1350 f/s is actually a long way from 1000 when considering sub vs. super sonic. (Most actual measurements of the sound barrier yield values closer to 1050 than 1150, and it's not a good idea to 'play around at the boundary if you are serious about preventing the supersonic "crack".) The 350 f/s difference is exacerbated by bullets with poor ballistic coefficients.

I'll run the diameter up to .510" and see what BC this bullet design yields.

Paul

Funny thing I've also been toying with the idea on subsonic loads based on the 6.5x52 Carcano round.

I too recognized most calibers and cartridge combination don't lend themselves very well because of standard barrel twists and excessive cartridge capacities.  However the 6.5 Carcano I have has a barrel twist somewhere about 8 the best I can measure and I have a cast bullet mould (the Cruise Missile) that drops a heavy flat-tipped bullet, 170 grains at .269 diameter and 1.280" long. One handicap for me is living at 5600 ft elevation so Mach 1 drops to approximately 1000 fps.

I've gotten these lead "spikes" to fly accurately over a reduced load of 9 to 10 grains of Unique but are well over Mach 1 with a noticible "crack".  To get down to less than 1000 fps I've calculated I'll need a load of 5.0 grains of Red Dot that fills the case to only 26%.  Trail Boss should be a better fill but I'll have to find that load by experimentation.

I plan to load up some of these "Cruise Missiles" with Red Dot and Trail Boss with Mag pistol primers and see if the Carcano barrel twist is enough to cut paper cleanly at 50 yds.  If they fly straight, then the next step would be to put the bullet's high sectional density to the test on penetration in some appropriate medium.

If resources weren't a restraint, I would think a 30 BR cartridge necked to 6.5mm, 30 and 338, loaded with heavy BT FMJs seated backwards, and mated to fast twist barrels would be the ticket to evaluate.  The 30BR case with its small primers strikes me to be better adapted to achieve powder burning at higher pressure and thus obtaining less variations in shot to shot velocities.

In my limited subsonic backyard safaris (potting pigeons) using CB 22 shorts, I've noticed the same effects as Gitano; they kill, but not instantly.

Nels

This is a good thread.
 
A couple of things I have noticed in reference to the "cylinder" projectile, not sure if this proves anything but;
 
I have been playing around with hard cast projectiles in my .308. They are 165gn, no gas check, powered by 18 gns AR2205. Not too sure of the velocity but they are supersonic.(1600fps?)
 
Anyway these projectiles have a large flat nose. When used on goats on chest and shoulder shots, the goats take a "whack", followed by a stumble and then they fall to the ground dead. The projectiles almost always exit so the energy developed at any given range is not fully used up in the chest cavity. Some of that energy is expended as the projectile hits the ground.
 
BUT, I have seen goats shot in the chest during culls with a .308 using mil. ammo, 144gn FMJ at approx. 2700fps. After the animal is hit it starts running flat out for 50 odd metres until it drops dead. Make no mistake, the FMJ projectiles do kill, but the behaviour of the animal after being hit is VERY different. Even though the FMJ has a much higher muzzle energy and any higher energy out to any given range.
 
I don't know why it is so but it is!
 
Any thoughts?

Nels,

The Carcano sounds like a good candidate for a subsonic cartridge. Based on the numbers you mention above - 170 grains, .269" diameter, and 1.28" long - the paper-whipping doesn't look good for that bullet at 1000 f/s at a twist of 1:8, though. See first two files below.

My BC calculator estimates the BC for that bullet between .48 and .5. Pretty good, so it should be an effective "hunter" out to 150 yds or so for head shots. The third image below is the trajectory table I came up with for that bullet shot at 5600 feet Above Sea Level and an estimated BC of .49.

Personally, I'd opt for the bullet design described above (I'll call it the "subsonic bullet" for this discussion), over the 170, just because of stability issues. Again as a personal matter, I'm not too fond of long bullets. To me, frontal area contributes more to "lethality" than weight/sectional density does, so if I've gotta stay with a given caliber, I don't care much how long it is. Precision and stability are my goals. This "attitude" was borne of breaking my sword trying to get long bullets (195-grain Barnes') to shoot in my 1:9.5 twist 7mm Rem Mag. No 'joy' there I can assure you.

As for reversed BTSP and BTHPs, I was never able to get them to shoot as straight (precisely) as in their normal orientation. That could easily be because I was trying to start them off just as fast reversed as I was with them normally oriented. However, my modest subsonic experiements didn't yield any different results, and terminal performance was "poor" because the beefed-up butt of the bullet didn't deform hardly at all - even at substantial supersonic (3000-ish f/s) MVs. Overall, they just didn't perform like I thought they would externally or terminally. It is largely due to the experience with reversed BT'd bullets that I decided to design my own projectiles - both for sub and super sonic flight.

22hornet -

Quotenot sure if this proves anything but;

May not "prove" anything, but it is certainly "another rock on the pile" for the "lethality" of blunt-nosed bullets. Your observations of the responses of game to FMJs are consistent with what I've seen as well.

QuoteAny thoughts?

My thoughts on this matter are summed up in the thread I started on "work". Put succinctly, blunt-nosed projectiles (and large-meplatted HPs) do more "work" on an animal than "pointy" ones do (especially FMJs) until the velocity of the pointy ones goes way up. The more work done, the faster the game animal loses its feet.[/SIZE][/FONT]

Paul

If you are trying to make a subsonic load work properly in a standard cartridge, say the 6.5 Carcano or .308 Win, and keeping with a standard twist rate for that cartrige, what is a better choice of projectile to use in order to make it fly straight and true. (No keyholing)A long pointy one or a short stubby one?