Anyone shoot 600 yds with their boolits?

[TD1886]

What makes you think the rotation slows that much? The only thing that would affect the rotation would be air friction against the rotation, dropping velocity would not have any affect on the rpm..

Oh my where to begin. Here's the formula for finding RPM. It's the velocity times the constant of 720 divided by the twist. Let's take a 308 shooting whatever bullet at 2800 fps and the barrel has a 12 twist. Multiplied by the constant of 720 gives you 2,016,000. Now divide that by the twist of 12 and you get 168,000 rpm. Now let's say that same bullet slows down to 2000 fps at some distance way out there, again figure the rpm with the formula given and you will see that the RPM is now 120,000 RPM. RPM has to have the velocity in the formula. What did you think that the muzzle RPM is going to stay at that figure, give or take a little for air friction? Well it doesn't.

[dverna]

Oh my where to begin. Here's the formula for finding RPM. It's the velocity times the constant of 720 divided by the twist. Let's take a 308 shooting whatever bullet at 2800 fps and the barrel has a 12 twist. Multiplied by the constant of 720 gives you 2,016,000. Now divide that by the twist of 12 and you get 168,000 rpm. Now let's say that same bullet slows down to 2000 fps at some distance way out there, again figure the rpm with the formula given and you will see that the RPM is now 120,000 RPM. RPM has to have the velocity in the formula. What did you think that the muzzle RPM is going to stay at that figure, give or take a little for air friction? Well it doesn't.

I don't believe it works that way. I do not have time now to research it, but I suspect others will be chiming in.

[TurnipEaterDown]

Yoy.

The formula for rotational speed based on bullet speed and twist only works for when the bullet travel is constrained by the rifling, and since change in linear velocity and rotational velocity is exceptionally small just after release, it works for muzzle condition as well.

The linear velocity (speed) of the bullet at any point in time is affected by frontal drag.
The rotational velocity is affected by the resistance of the bullet in a boundary layer of air surrounding the bullet. Very different than frontal drag.
The spin rate imparted at the end of the rifling, being required to stabilize the bullet (it is not fin stabilized like a arrow / missle) is what maintains stability THROUGHOUT flight.
This is well documented.

If rotational velocity slowed in a direct linear manner with the linear forward velocity ("speed") of the bullet, accurate long range shooting w/ common projectiles would be nearly impossible. It is Very easy to change a bullet from an unstable condition to stable, with a twist rate change of just 10% -- look at 100 gr ish 6mm VLDs. Not stable in 1:10, stable in 1:9 in common cartridges 3100 fps or so.
Is the conjecture seriously that these bullets become unstable when they lose 10% of forward velocity? Hardly. Low drag bullets Have to remain stable at long ranges, where they have lost Significant forward velocity. Long range precise shooting is their 'reason to be'.

How fast would a person need to twist a 50 BMG with something like a 750 A Max / 800 Barnes to make accurate hits at 2800 yds, if this conjecture were true? It's easy to find the residual velocity in those conditions. Accurately placed hits have been made at these distances with that and comparable cartridges.

It is even hard to find guidance on how many yards it takes for a bullet to lose stability in flight given a set of muzzle conditions -- this should give pause for thought. It is rarely a concern to most people.


Bullets do Not lose rotational velocity at the same rate as linear velocity.
Completely different drag forces at work here.

[TD1886]

Yoy.

The formula for rotational speed based on bullet speed and twist only works for when the bullet travel is constrained by the rifling, and since change in linear velocity and rotational velocity is exceptionally small just after release, it works for muzzle condition as well.

The linear velocity (speed) of the bullet at any point in time is affected by frontal drag.
The rotational velocity is affected by the resistance of the bullet in a boundary layer of air surrounding the bullet. Very different than frontal drag.
The spin rate imparted at the end of the rifling, being required to stabilize the bullet (it is not fin stabilized like a arrow / missle) is what maintains stability THROUGHOUT flight.
This is well documented.

If rotational velocity slowed in a direct linear manner with the linear forward velocity ("speed") of the bullet, accurate long range shooting w/ common projectiles would be nearly impossible. It is Very easy to change a bullet from an unstable condition to stable, with a twist rate change of just 10% -- look at 100 gr ish 6mm VLDs. Not stable in 1:10, stable in 1:9 in common cartridges 3100 fps or so.
Is the conjecture seriously that these bullets become unstable when they lose 10% of forward velocity? Hardly. Low drag bullets Have to remain stable at long ranges, where they have lost Significant forward velocity. Long range precise shooting is their 'reason to be'.

How fast would a person need to twist a 50 BMG with something like a 750 A Max / 800 Barnes to make accurate hits at 2800 yds, if this conjecture were true? It's easy to find the residual velocity in those conditions. Accurately placed hits have been made at these distances with that and comparable cartridges.

It is even hard to find guidance on how many yards it takes for a bullet to lose stability in flight given a set of muzzle conditions -- this should give pause for thought. It is rarely a concern to most people.


Bullets do Not lose rotational velocity at the same rate as linear velocity.
Completely different drag forces at work here.

I'll agree with you a lot of what you said. I never said that rotational velocity was lost at the same rate. I said it does get lost though.

What in your opinion causes a bullet to become unstabilized? Is it a big decrease in velocity, or is a big decrease with velocity and also rotational velocity? Add gravity. I have a good video to show you all if a friend of mine sends it to me.

[TurnipEaterDown]

... Now let's say that same bullet slows down to 2000 fps at some distance way out there, again figure the rpm with the formula given and you will see that the RPM is now 120,000 RPM. ....

Plain reading, I took this statement to mean that rotational velocity could be computed based on speed of bullet at a point in flight, and that is what I had disagreed with and sought to correct.

What causes a bullet to destabilize?
There are a number of factors.

Forces on the bullet will be non uniform upon Exit from the muzzle shot to shot -- usual clues about this are poor precision capability (aka bad groups).
Uniformity of these forces (or lack of) can be exacerbated by muzzle condition, bullet mass center concentricity w/ geometric center, diameter of bullet base versus muzzle exit ID, etc.
These forces can affect the general stability of the bullet (yaw), and might lead to stability issues, but generally would be more prone to flight path predictability issues unless really bad things were happening. (aka just "bad groups", and not usually a "hey, where did that one go?")
Make these factors really extreme by getting a cast bullet to size a bit off axis, or use ones that have notable voiding or bases not perpendicular to geometric form, and profound lack of stability is nearly assured (the "hey, where did that go", or keyholes in target paper).

With "good" bullets, stability I think often gets challenged as a bullet crosses the sound barrier.
Good LR target bullets (I am thinking about jacketed) seek to have a form that minimizes buffeting effect (uneven force distribution, of a chaotic manner) when a bullet crosses the speed of sound -- dropping below sonic. That, AND / OR the manufacturer Tells You where (given a muzzle velocity) the bullet will no longer stay sonic. (Can be computed with BC & MV.) No accident they tell you this for a factory load, as in sniping. Crossing the sound barrier is rough on flight path control.
I don't know how many cast bullets really take this into effect. I suspect few. I suspect that a notable exception to this is the "good" (i.e. competative) BP Cartridge bullets that are shot at 1000 yds. They start fairly slow. I would believe that they must cross sonic well before the target. Yet they shoot well. The good ones must minimize flight path disruption crossing the sound barrier.
A good indicator to look for on this is: The load shoots well at 50 yd, 100 yd, 150 yd, X yd, with (nearly) linear group size expansion, and then, next yardage mark the group size opens up in relationship to distance. If that is seen, good bet that bullet path has been disrupted, and not just that the shooter had bad habits that show up at long range.
If you ever see this, use a BC calculator for the bullet (some makers might provide), measure MV, and calculate where the bullet goes sub sonic. Likely will be telling.
(BTW: BCs calculated on form are often off. Also, measured may be different from even a good maker published number -- Barnes X bullets used to have optimistic published numbers. Third, if a person calculates the true BC of a projectile shot from a firearm they will likely find it varies shot to shot, and that the same bullet shot from different guns may show a marked difference -- say maybe up to 10%, which is an indication of poor stability (or excess yaw) at the muzzle for ones computing lower than others or very much lower like that 10%.)

Also, just what is stability?
A bullet can precess and still be stable. Precession, as noted, is a yawing of the bullet motion axis along the flight path while in flight.
In fact, to some degree, all bullets precess in flight.
Stability should not be looked at as a bullet purely spinning about its own geometric axis, aligned precisely with the axis of the flight path (technically what many would think of is really the the instantaneous tangent to the flight path). Bullets just don't act like that.

A good quick read on some of this is in the A-Square manual: "Any Shot You Want", pages 117-127, where bullet penetration is discussed.
Bullet rotation keeps the bullet stable while penetrating an object as well.

Distinctly, on page 118 it states: "The bullet retains the vast majority of its rotational velocity throughout its flight."

A final note:
Marginally stabilized bullets (just enough rifling twist) are poor penetrators.
"Over twisted" guns (a significantly higher rate of twist than necessary for flight stability) produce better penetration in game. Why? As the bullet expands its frontal area it requires more spin to remain stable than an undistorted form (Corrected / expanded: initial spin must be high enough that Sufficient spin rate is Maintained to keep the bullet stable during expansion, as conservation of momentum dictates that rotational Velocity will Slow as the bullet expands). It can NOT speed up (edited / expanded, the bullet can not gain rotational momentum), the forces are long gone to do that. It must be spinning fast enough that it Can expand and Still be stable. This would be "over stabilized" for pure flight in air.

A thing I remember being told (older V'Nam era gents w/ knowledge might confirm): Early M16s were provided for combat use w/ twist & bullet weight/form that produced a somewhat "threshold stability" of the bullet in flight, with the Express Intent to have the bullet Destabilize once in the target body, to create a larger wound channel. FMJs don't really expand, a bullet badly yawing or tumbling causes a bigger hole. At least I was told the designers did this.
Must not have worked out too well, I was also told this wasn't kept up too long. Perhaps the twist was increased, pretty sure the bullets were redesigned. Likely both.

[TD1886]

Plain reading, I took this statement to mean that rotational velocity could be computed based on speed of bullet at a point in flight, and that is what I had disagreed with and sought to correct.

What causes a bullet to destabilize?
There are a number of factors.

Forces on the bullet will be non uniform upon Exit from the muzzle shot to shot -- usual clues about this are poor precision capability (aka bad groups).
Uniformity of these forces (or lack of) can be exacerbated by muzzle condition, bullet mass center concentricity w/ geometric center, diameter of bullet base versus muzzle exit ID, etc.
These forces can affect the general stability of the bullet (yaw), and might lead to stability issues, but generally would be more prone to flight path predictability issues unless really bad things were happening. (aka just "bad groups", and not usually a "hey, where did that one go?")
Make these factors really extreme by getting a cast bullet to size a bit off axis, or use ones that have notable voiding or bases not perpendicular to geometric form, and profound lack of stability is nearly assured (the "hey, where did that go", or keyholes in target paper).

With "good" bullets, stability I think often gets challenged as a bullet crosses the sound barrier.
Good LR target bullets (I am thinking about jacketed) seek to have a form that minimizes buffeting effect (uneven force distribution, of a chaotic manner) when a bullet crosses the speed of sound -- dropping below sonic. That, AND / OR the manufacturer Tells You where (given a muzzle velocity) the bullet will no longer stay sonic. (Can be computed with BC & MV.) No accident they tell you this for a factory load, as in sniping. Crossing the sound barrier is rough on flight path control.
I don't know how many cast bullets really take this into effect. I suspect few. I suspect that a notable exception to this is the "good" (i.e. competative) BP Cartridge bullets that are shot at 1000 yds. They start fairly slow. I would believe that they must cross sonic well before the target. Yet they shoot well. The good ones must minimize flight path disruption crossing the sound barrier.
A good indicator to look for on this is: The load shoots well at 50 yd, 100 yd, 150 yd, X yd, with (nearly) linear group size expansion, and then, next yardage mark the group size opens up in relationship to distance. If that is seen, good bet that bullet path has been disrupted, and not just that the shooter had bad habits that show up at long range.
If you ever see this, use a BC calculator for the bullet (some makers might provide), measure MV, and calculate where the bullet goes sub sonic. Likely will be telling.
(BTW: BCs calculated on form are often off. Also, measured may be different from even a good maker published number -- Barnes X bullets used to have optimistic published numbers. Third, if a person calculates the true BC of a projectile shot from a firearm they will likely find it varies shot to shot, and that the same bullet shot from different guns may show a marked difference -- say maybe up to 10%, which is an indication of poor stability (or excess yaw) at the muzzle for ones computing lower than others or very much lower like that 10%.)

Also, just what is stability?
A bullet can precess and still be stable. Precession, as noted, is a yawing of the bullet motion axis along the flight path while in flight.
In fact, to some degree, all bullets precess in flight.
Stability should not be looked at as a bullet purely spinning about its own geometric axis, aligned precisely with the axis of the flight path (technically what many would think of is really the the instantaneous tangent to the flight path). Bullets just don't act like that.

A good quick read on some of this is in the A-Square manual: "Any Shot You Want", pages 117-127, where bullet penetration is discussed.
Bullet rotation keeps the bullet stable while penetrating an object as well.

Distinctly, on page 118 it states: "The bullet retains the vast majority of its rotational velocity throughout its flight."

A final note:
Marginally stabilized bullets (just enough rifling twist) are poor penetrators.
"Over twisted" guns (a significantly higher rate of twist than necessary for flight stability) produce better penetration in game. Why? As the bullet expands its frontal area it requires more spin to remain stable than an undistorted form (Corrected / expanded: initial spin must be high enough that Sufficient spin rate is Maintained to keep the bullet stable during expansion, as conservation of momentum dictates that rotational Velocity will Slow as the bullet expands). It can NOT speed up (edited / expanded, the bullet can not gain rotational momentum), the forces are long gone to do that. It must be spinning fast enough that it Can expand and Still be stable. This would be "over stabilized" for pure flight in air.

A thing I remember being told (older V'Nam era gents w/ knowledge might confirm): Early M16s were provided for combat use w/ twist & bullet weight/form that produced a somewhat "threshold stability" of the bullet in flight, with the Express Intent to have the bullet Destabilize once in the target body, to create a larger wound channel. FMJs don't really expand, a bullet badly yawing or tumbling causes a bigger hole. At least I was told the designers did this.
Must not have worked out too well, I was also told this wasn't kept up too long. Perhaps the twist was increased, pretty sure the bullets were redesigned. Likely both.

Interesting. I want to talk about that twist on the M16's. When I got my first AR-15 I got one with a 7 twist. I shot all kinds of game and varmints with it. When I first reloaded for it I was using the surplus 55 grain FMJ's Nam issue. Well I figured these are okay for just plinking, but not hunting. I was wrong. They exploded varmints like that has C4 in them. Praire dogs were totally obliterated. Groundhogs torn in two pieces, etc. I was hunting praire dogs one day and ran into a fellow hunting too and he had 22-250. We shot them together. Then he asked me what the hell bullet are you shooting. I asked why and he said your bullet is tearing them up far worse then my bullets. I showed the FMJ's and he was shocked. He was shooting soft points, 55 grains if I remember. I told him that I was told by Sierra it was 7 twist spining them up so fast that when they hit anything they blew up. Years after that I was having a discussion on AR15.COM which Navy Forensics doctor. I tolk him I think the 7 twist increases bullet damage to tissue. He totally disagreed and went on to say that was part of his job and he examined many many wounds and did not see that from the 7 twist. You got energy put into the bullet both my forward velocity and rotational velocity. The rotational velocity on a .224 bullet fired from a 7 twist is quite high! Who to believe.

[TurnipEaterDown]

Hard to say why your FMJs we acting the way you describe out of a 1:7 twist barrel.
I know nothing of the bullet you were shooting.

In general, military FMJs are not thin enough of a jacket to create a problem w/ rotational integrity due to centrifugal force issues when spun faster, nor have the rifling cut the jacket so bad it is weakened. So, if it retains it's form, higher than designed spin rate just makes it more stable as it slows in a body.
But again, I don't know anything about that bullet. Perhaps it did have a thin jacket. Folks at ammunition companies know more about ammunition than I.

When a thin jacket bullet is weakened by the rifling form cutting into it, and it is spun too fast, it simply unravels in air or when it first gets disturbed hitting something. Very common experience w/ Hornady 22 SX bullets in high twist 22s. They tear apart in mid air -- not enough jacket strength to contain the hoop stress produced by firing, and "poof" -- grey cloud somewhere down range. The often cited example is shooting those in a 1:7 223/5.56.
If any bullet is spun at the limit of its integrity, when it touches/hits something, it is going to rapidly expand/tear itself apart.

Heck, my 1:9 22-250 did that with some 52 grain flat base Bruno bullets I tried. New barrel it worked for a little while, and I got tiny groups. Within a couple weeks they all went "poof" about 20 yds out, the box was 1/2 gone, so I gave the rest away and spent my time w/ 68, 69 & 75 gr boat tails that I put it together for. Many years later, and hundreds of rounds more, the 68, 69 and 75s all shoot little groups.

I was told at one time that one design of military small arm projectile played with center of gravity to make it destabilize more easily in a body. Whether that was some other 5.56 round, I don't know / remember.

All this is "old" science. I imagine that every country that ascribed to the "dum dum bullet" agreement in treaty coming out of WWI that forbid the use of expanding bullets in military small arms / anti-personnel figured out ways around expansion to increase wounding.

Really, from what I was taught, it's really best to not kill the enemy when shot. Just wound them horribly, and decapacitate. Civilized combatants will then expend resources on field medical care. Sucks up more personnel. Or, so goes the theory. Suppose it doesn't work too well in any regard w/ some folks our US military engages these days anyway. They don't seem too civilized to me.

Lots of things are going on when a bullet hits a body.
Don't really know the explanation for your experience.

[TD1886]

Hard to say why your FMJs we acting the way you describe out of a 1:7 twist barrel.
I know nothing of the bullet you were shooting.

In general, military FMJs are not thin enough of a jacket to create a problem w/ rotational integrity due to centrifugal force issues when spun faster, nor have the rifling cut the jacket so bad it is weakened. So, if it retains it's form, higher than designed spin rate just makes it more stable as it slows in a body.
But again, I don't know anything about that bullet. Perhaps it did have a thin jacket. Folks at ammunition companies know more about ammunition than I.

When a thin jacket bullet is weakened by the rifling form cutting into it, and it is spun too fast, it simply unravels in air or when it first gets disturbed hitting something. Very common experience w/ Hornady 22 SX bullets in high twist 22s. They tear apart in mid air -- not enough jacket strength to contain the hoop stress produced by firing, and "poof" -- grey cloud somewhere down range. The often cited example is shooting those in a 1:7 223/5.56.
If any bullet is spun at the limit of its integrity, when it touches/hits something, it is going to rapidly expand/tear itself apart.

Heck, my 1:9 22-250 did that with some 52 grain flat base Bruno bullets I tried. New barrel it worked for a little while, and I got tiny groups. Within a couple weeks they all went "poof" about 20 yds out, the box was 1/2 gone, so I gave the rest away and spent my time w/ 68, 69 & 75 gr boat tails that I put it together for. Many years later, and hundreds of rounds more, the 68, 69 and 75s all shoot little groups.

I was told at one time that one design of military small arm projectile played with center of gravity to make it destabilize more easily in a body. Whether that was some other 5.56 round, I don't know / remember.

All this is "old" science. I imagine that every country that ascribed to the "dum dum bullet" agreement in treaty coming out of WWI that forbid the use of expanding bullets in military small arms / anti-personnel figured out ways around expansion to increase wounding.

Really, from what I was taught, it's really best to not kill the enemy when shot. Just wound them horribly, and decapacitate. Civilized combatants will then expend resources on field medical care. Sucks up more personnel. Or, so goes the theory. Suppose it doesn't work too well in any regard w/ some folks our US military engages these days anyway. They don't seem too civilized to me.

Lots of things are going on when a bullet hits a body.
Don't really know the explanation for your experience.

Hell there even was a story going around in Nam about smooth bore barrels on M16's. IF IF it were true you would never find documentation on you.

Okay I got the bullet spinning on ice for you. You'll see it close up about 3/4 the way throught. I'd totally amazing. All you others watch it too, I promise you it's something to see.

[mace2364]

Perhaps I can shed a little light on the M16 rifling twist rate.

The first AR15s(before they were officially M16s), had a 1/14 twist. This was chosen simply because that was the commonly accepted twist rate for .22 caliber centerfires of the day(think .222, etc), and because that’s what the barrel makers did. Winchester actually made barrels for Armalite/Colt for the first military AR15s (called model 601s, if you’re interested)Those rifles were sent to Vietnam in what amounted to field testing in the early 60’s. They figured out that in certain conditions the 55gr FMJBT bullet (also a brand new design) was not being stabilized by the 1/14 twist rate. In a chunk of the areas of the conflict where it was being used, this was the case but it didn’t cause a problem because the contact distances with the enemy were so close. And there are detailed combat reports of the crazy terminal effects of these unstabilized bullets. That’s where those old rumors of “tumbling bullets”came from. But important to note, this was only the first several thousand rifles(I think the number was 8500) and this was ALL in the advisor era, pre-1965. The guy I knew who was involved, was there in 1962, and was an advisor to the Vietnamese Paratroops. Regrettably he is deceased now.

At any rate, with the next models that came out, they went to a 1/12 twist. This corrected the stabilization issue. All military rifles produced after the Colt/Armalite 601 would’ve had this twist rate. Commercial Colts are another matter, and beyond the scope of this discussion. To be sure, some of these older rifles did remain is service(the Air Force is notorious for this), but simple production numbers of this older model show that there just weren’t THAT many of them out there, relatively speaking. This 1/12 twist rate would be the standard all the way into the mid-80’s with the M16A2, and NATO standardizing 5.56mm.

If you’re interested-all of this information and a whole lot more is available in a book-I believe it was called “The Black Rifle” or something like that. There are also piles of military documents on this topic. If you happen to look at those and see the name “Garland Wright”, that was my friend.

Anyway, with the M16A2 came the 1/7 twist rate. This was done to stabilize the M855 ball, and the even longer M856 tracer. Both of these bullets are rather long for their weight and caliber, because they both use materials lighter than lead in a portion of their construction. Twist rate pertaining to bullet length rather than weight. This 1/7 twist rate is still in usage with issued weapons as far as I know(I can personally account for it up to 2010). And contrary to internet nonsense, you can indeed shoot 55gr ammo through a 1/7 barrel just fine-having done it out to distance many times.

Kinda funny how that old gun shop tale of tumbling bullets hangs on after this many years, having only involved a few thousand rifles 50+ years ago.

[TD1886]

Perhaps I can shed a little light on the M16 rifling twist rate.

The first AR15s(before they were officially M16s), had a 1/14 twist. This was chosen simply because that was the commonly accepted twist rate for .22 caliber centerfires of the day(think .222, etc), and because that’s what the barrel makers did. Winchester actually made barrels for Armalite/Colt for the first military AR15s (called model 601s, if you’re interested)Those rifles were sent to Vietnam in what amounted to field testing in the early 60’s. They figured out that in certain conditions the 55gr FMJBT bullet (also a brand new design) was not being stabilized by the 1/14 twist rate. In a chunk of the areas of the conflict where it was being used, this was the case but it didn’t cause a problem because the contact distances with the enemy were so close. And there are detailed combat reports of the crazy terminal effects of these unstabilized bullets. That’s where those old rumors of “tumbling bullets”came from. But important to note, this was only the first several thousand rifles(I think the number was 8500) and this was ALL in the advisor era, pre-1965. The guy I knew who was involved, was there in 1962, and was an advisor to the Vietnamese Paratroops. Regrettably he is deceased now.

At any rate, with the next models that came out, they went to a 1/12 twist. This corrected the stabilization issue. All military rifles produced after the Colt/Armalite 601 would’ve had this twist rate. Commercial Colts are another matter, and beyond the scope of this discussion. To be sure, some of these older rifles did remain is service(the Air Force is notorious for this), but simple production numbers of this older model show that there just weren’t THAT many of them out there, relatively speaking. This 1/12 twist rate would be the standard all the way into the mid-80’s with the M16A2, and NATO standardizing 5.56mm.

If you’re interested-all of this information and a whole lot more is available in a book-I believe it was called “The Black Rifle” or something like that. There are also piles of military documents on this topic. If you happen to look at those and see the name “Garland Wright”, that was my friend.

Anyway, with the M16A2 came the 1/7 twist rate. This was done to stabilize the M855 ball, and the even longer M856 tracer. Both of these bullets are rather long for their weight and caliber, because they both use materials lighter than lead in a portion of their construction. Twist rate pertaining to bullet length rather than weight. This 1/7 twist rate is still in usage with issued weapons as far as I know(I can personally account for it up to 2010). And contrary to internet nonsense, you can indeed shoot 55gr ammo through a 1/7 barrel just fine-having done it out to distance many times.

Kinda funny how that old gun shop tale of tumbling bullets hangs on after this many years, having only involved a few thousand rifles 50+ years ago.

Thanks for the report. I do have that "Black Rifle" book among others. It's a pretty decent book.

As a test one time I pulled some 22 magnum 40 grain hollowpoints and loaded over my standard 55 grain .224 bullets. I was getting rattled by others that my 7 twist would destroy those rimfire bullets. Well it didn't and they all shot fine. Now the truth, no I didn't shoot them out to 100 yards. I shot them all close. My rifle also shot 22 LR's decent with the conversion kit. Good enough to take squirrels with close shot. I made sure I used the largest diameter bullets and at that time they were PMC.

I have a few industry friends that say the M16 might have been a tad better if they used the 222 Remington case. The theory is that the shorter case, and longer neck, would keep the bullets out of the powder capacity and have no problem with longer bullets. You have to admit the 222 and 223 are very close in ballistics and if the military made the new 222 Rem case round as hot as the 5.56 NATO rounds on it would have worked. As we know they "say" that the 223 Remington Magnum was suppose to be the M16 round. I wonder how much that would have changed things? For one we would have longer magazine well and the crazy way they have made about ever conceivable wildcat for the AR15, it would have given them more room.

[TurnipEaterDown]

Perhaps I can shed a little light on the M16 rifling twist rate.
....
Kinda funny how that old gun shop tale of tumbling bullets hangs on after this many years, having only involved a few thousand rifles 50+ years ago.

Appreciative Thanks.
I don't much have an attraction to most of the AR platform, so this helps my knowledge base on the 5.56 history.

As you also allude to, the "over twisted" conversation also has longer legs than it should.
Light/short bullets for a given twist can shoot great out of a good rifle -- though they do tend to go "nose up" at very long range, thus degrading BC and creating a less optimal impact angle for terminal ballistics. I think the reason my Bruno 52s began to "poof" was the throat likely roughened up a bit in my 22-250 after development on multiple loads.

[TD1886]

Appreciative Thanks.
I don't much have an attraction to most of the AR platform, so this helps my knowledge base on the 5.56 history.

As you also allude to, the "over twisted" conversation also has longer legs than it should.
Light/short bullets for a given twist can shoot great out of a good rifle -- though they do tend to go "nose up" at very long range, thus degrading BC and creating a less optimal impact angle for terminal ballistics. I think the reason my Bruno 52s began to "poof" was the throat likely roughened up a bit in my 22-250 after development on multiple loads.

You just aren't whistling Dixie about over twist having longer legs then it should. I agree 1000%. I'm tickled to death and these hot calibers in 6mm, 6.5mm, and 7mm have exceptionally fast twists and are working out very well with terriffic accuracy. SURE fast twist is hard on cast bullets, just about anyone here knows that.

[supersniper]

With the right alloy... copper added and heat treated.... cast boolits can be pushed as fast as jacketed in slower twists and nearly jacketed speeds in faster twist barrels. There is an RPM speed limit for your particular alloy.

[405grain]

"Starting at the muzzle at 2200 fps my Mauser spins the bullet at 171 K. At 600 yards that rpm has decayed to 97K. That's a huge drop."

It doesn't work that way. Any bullet, even a full wadcutter, when traveling at supersonic speed will be traveling in a low pressure region (close to a vacuum) because it is behind the shock wave. Like a top spinning in a vacuum the rotational speed of a bullet will slow very very little during it's flight so long as it remains supersonic. The higher the ballistic coefficient a bullet has the longer it's time of flight will be before it enters the transonic zone. When a bullet decelerates from supersonic to subsonic the shock wave will collapse on the bullet and it will begin experiencing atmospheric surface drag. Many aerodynamic factors may influence bullet stability once it has transitioned through the transonic zone. If your bullet has a high enough BC to remain supersonic beyond 600 yards its rotational speed will still be more than 99% of what it was at the muzzle.

Another it doesn't work that way is the misconception that spin rate plays any part on a bullet's destabilization when striking a flesh and bone target. The instability of full metal jacket spitzer bullets is caused by their rapid deceleration. The aerodynamic shape of a spitzer bullet requires that the bulk of the mass of the bullet is in the bullet's base. Where a soft nosed spitzer bullet will deform upon impact, a full metal jacket bullet, for the most part, will not. Since the base of the bullet has the most mass, and hence the most inertia, the front of the bullet will tend to decelerate more quickly than the base, and this will cause the bullet to tumble. Because the bullet is traveling at high velocity, and the cross section of the target (in military applications: some unlucky guy) is usually only a few inches thick, the bulk of the actual bullet tumbling occurs after it has passed through the target.

Last thing: not to nit pick, but the 30-06 was not designed for a 200 grain bullet. In 1903 the Army adopted the 30-03 cartridge. The 30-03 had a long neck (like the 30-40 Krag), and was designed to use the same bullet as the Krag. Then, in 1905 Germany introduced the high velocity spitzer bullet, whose lethality was caused by hydraulic shock instead of penetration. The United States modified the case neck dimensions on the 30-03 cartridge to accommodate a shorter and lighter pointed bullet. This new cartridge was called the 30-06. Because many thousands of model 1903 rifles had already been issued for the 30-03, they were recalled, then the barrels were set back and rechambered for the new 30-06.