You didn't respond to dddoo7's post but he was spot-on. Your bullet
will be more stable if it's loaded backwards, ogive in, base out. Or at least more
nearly stable. Whether that will be stable
enough, I couldn't tell you. And at SS velocities, it probably also will have better terminal effects flying base-first.
The 'standard' rate of twist for the 300 AAC/Blackout/Whisper is 1:8, so I'd expect a spot of bother from any .30 caliber bullet shot through a 1:11 (but that doesn't mean it can't be made to work). The 300 AAC needs a tighter twist because subsonics are harder to stabilize.
From "Applied Ballistics for Long Range Shooting", Bryan Litz, ISBN-13: 978-0615452562
This represents the relationships of the key players, Center of Gravity (CG) and Center of Aerodynamic Pressure (CP), in a streamlined, pointy-nosed bullet. Two things to note. First, the CP is in front of the CG. This is why the bullet is un-stable to begin with. And second, the CG is
way back in the thick end of the bullet.
Every moving object that travels with its CP forward of its CG has negative static stability (= is unstable). It's why rear-engined cars (Chevy Corvair & Porsche 911) have notoriously tricky handling. It's why you put fins on a rocket or fletchings on an arrow, why they put tails on kites and why a 4th of July bottle rocket is stable in flight with nothing any more hi-tech than a skinny stick trailing behind it. All examples of devices that do nothing more than create a little extra drag aft of the CG, producing positive static stability in the doing.
We see the same principle demonstrated in the design of a "diabolo"-style airgun pellet, which has as much mass as possible crammed up near the nose, putting CG as near as possible to the tip, and a wide, flared skirt to add drag at the back.
Which is why pellets are stable, even when fired from a smooth-bore "b.b. gun." Yes, they are more accurate when fired through a rifled barrel, but accuracy is a completely different subject from stability. Similarly,
arrows are more accurate if the fletchings have a bit of "helical" to cause them to spin in flight, but they still are perfectly stable with no helical.
A bullet flying with its CP ahead of its CG (as is its norm) has the same problem as an arrow that has been shot fletchings first. It is unstable and wants very much to turn around. In the bullet's case, what is required to prevent it doing so is the
conservation of angular momentum, or what is commonly referred to as "gyroscopic force." Spin.
A number of properties affect how fast a bullet has to be spun to make it stable. The one that is relevant to this conversation also is the one that changes constantly through the flight of the bullet, the distance between the CP and the CG: the CP-CG moment arm. Like the CG is the point around which all the gravitational forces are balanced, the CP is the point around which all aerodynamic forces are balanced. Except gravity is a constant, so the CG always is in the same spot. CP, OTOH, is the result of the pressures from the air flowing around the bullet, so CP moves any time there is a change to the airflow.
The longer that moment arm is, the CP-CG moment arm, the more pronounced the object's stability (or instability) will be. So in a pointy bullet, the further apart those two points are, the more unstable it is and the harder it has to be spun.
As this chart shows, the supersonic shockwave creates a several fold increase in aerodynamic drag. But it doesn't only affect the bullet at its tip, it also occurs down its flanks. And the fact of adding drag down the sides causes the CP to move away from the nose and nearer to the CG. Which shortens the CP-CG moment arm. Which makes the bullet less un-stable and easier to stabilize.
All of which goes to why a bullet designed for supersonic flight becomes harder to stabilize when it loses the supersonic shockwave. And why any pointy-nosed bullet is easier to stabilize when you shoot it ass-end first.
So dddoo7 wasn't pulling your chain. Your 168-gr Speers
will come closer to being stable if you shoot them backwards. And a subsonic bullet has no "hydrostatic shock" to enhance terminal effects, but it will cause tissue to have to move more violently to get out of the bullet's way if it impacts blunt end first. So you'll probably get better terminal effects in the bargain.
