225415- .22 hornet update

[mainiac]

You folk might remember my ramblings about this subject,last fall before ol-man winter set in. Well i got out today and shot somemore. Refining my loads,i found multiple 1 inch groups @ 90 yards (You have to shoot whereever you can this time of year!) 9 grs of h4227, 11.2grs of imr4198,and 11.3 grs of H4198sc, are all inch group loads! Guess what? they all go between 2373,and 2400 f.p.s. It seems that r.p.ms are at play here! Dont think it is barrell harmonics,because the gun is a stevens 322,with the stupid barrell band, couldnt float the barrell if i wanted! Anyway, i bet when i try other loads again, and strive for 2400 f.p.s., ill be smilin!

[Bass Ackward]

You folk might remember my ramblings about this subject,last fall before ol-man winter set in. Well i got out today and shot somemore. Refining my loads,i found multiple 1 inch groups @ 90 yards (You have to shoot whereever you can this time of year!) 9 grs of h4227, 11.2grs of imr4198,and 11.3 grs of H4198sc, are all inch group loads! Guess what? they all go between 2373,and 2400 f.p.s. It seems that r.p.ms are at play here! Dont think it is barrell harmonics,because the gun is a stevens 322,with the stupid barrell band, couldnt float the barrell if i wanted! Anyway, i bet when i try other loads again, and strive for 2400 f.p.s., ill be smilin!


Change your lube or change your bullet hardness either way and see what happens. If it's RPMs, then it will make no difference.

[mainiac]

Bass, why is it that i find this old gun to be my most shot castgun? I paid about a hundred bucks 15 years ago or so for it, it has the cheapest junk 4x bushnell scope you can imagine,and a homegrown scope mount that i cobbled together,and tig welded.You mention changing lubes and hardness.......... MAN, theres so many variables,that it is doubtful that i could try everything in the rest of my lifetime. Id like to get away from this thing,thank-you very much! But, the more I play with it,i cant leave it alone. I guess the first time i shot cast in it,with straight lino,and couldnt shoot 15 inch groups@ 50 yards,i should have known that id be spending some time with this beast. As to the r.p.m. thing, the bore is .2234,and has a 16 inch twist. Tight and very slow for this 48 gr bullet.Under 1700 f.p.s., and the boolets tumble. My benchrest guns are similar, just barely stabilized,so you can pour the coal to them,and dont they shoot this way!

[DonH]

mainiac;

When I get my Hornet going I will be pleased to get those groups (appr. m.o.a.). The bit of work I have done so far with small .22 CFs and cast has not been that good. Also, never sell those old ugly Stevens 322s/Savage 340s short. Benchrest rifles they aren't but they have always seemed to defy a few iron-clad rules about what it takes to shoot straight. A brother had the Savage in .222 once and it too with a cheap 4X scope was a m.o.a. rifle.
As for your loads, lubes, etc, experiment if you like but don't throw away the recipe you are using - you know, if it ain't broke....?

[Bass Ackward]

You mention changing lubes and hardness.......... MAN, theres so many variables,that it is doubtful that i could try everything in the rest of my lifetime. Id like to get away from this thing,thank-you very much! But, the more I play with it,i cant leave it alone.


You have the disease. Now your hooked. Yaz just gots to know. :grin:

You are in the only caliber that ever beat me into submission. One group .250, then an hour later 1 1/2". I could never get it to settle down until I got up to the Mashburn Bee case. Then temperature sensitivity of the powder was minimized enough because of the larger case capacity, I could hold consistent groups. Drove me crazy for a couple of decades.

Your results mirror mine. As we gain time, we get time to think. So I will try again.

You can drive a bullet too slow to stabilize. This is a very common problem with cast in handguns, even with their faster twist rates, which is why the Keith bullet does so well with weight on the back to make it easier to stabilize at lower velocities. But even this design will destabilize eventually. My 14 twist Whelen won't hold 2" below 1900 fps.

It's velocity that stabilizes at a certain center of pressure according to NASA. And the worse balanced a bullet is, the more velocity you need TO stabilize it. A bullet can be molded perfectly and still be outta balance unless you drive it at the right velocity. Bullet balance can come from design. But it can be improved or worsened by the center of pressure which constantly changes based on design and the level of deformity.

If you want to shoot a balanced bullet technique, then it will do well up until that bullet becomes too unbalanced. That doesn't mean it didn't deform, just that it deformed uniformly and your velocity was sufficient to stabilize it. That "pressure level" that it took to get you to that velocity level can be elongated and tweaked. But, in the end, you will lose accuracy when either you go so slow in burn rate that ignition consistency fails, OR you do not have enough velocity to stabilize that deformed bullet at that level.

RPM theorists stop right there. If you have the case capacity and throat dimensions to maintain alignment and can take that bullet on up in pressure until you reach the required velocity level, and your barrel has a harmonic node at that point, then the higher velocity will stabilize a deformed bullet again assuming that it deforms consistently. I find harmonics to be the real limiter here as each barrel is different. Just depends if you want to explore what you have.

Which technique will produce the best accuracy? It depends on how your barrel harmonics are at that node. Harmonics does play way less of a part at what are normally thought of as cast velocities, so "easiest accuracy" occurs .... down there. That's why I find that harder bullets shoot better in rifles. Less obturation, less vibration, less harmonics. So while the common logic is to go harder to go faster, it isn't always the case if it's too hard to deform uniformly with the case capacity you have to work with. So I shoot hard slow and softer fast.

Some guys claim good accuracy with Hornets to the 2800 fps level. But that has to be pushing the pressure limit of that cartridge. Since I failed with this caliber, I am in no position to comment. :grin:

[hornetguy]

I've shot this boolit once or twice in my K-Hornet with fair results at 100yds. IIRC, about 2-3" groups. I think I was at about 2000fps. Before I could do more playing, I got sidetracked on several other projects.
My rifle is pretty much MOA with jacketed.

[trooperdan]

Do you guys know of a boolit that will stablize below 1200fps in the Hornet? Yeah, I know, buy a .22 LR! I'm looking for a good "back-yard" plinking load.

[felix]

Dan, for that 16 twist you don't want any wind friction. The point cannot be any blunter (in effect) than the normal LR boolit. A sharp truncated cone might be a winner, for example. Keep in mind that weight is your friend, and length is your enemy. This means bismuth instead of antimony for hardening. German pellets would be your casting source. ... felix

[Larry Gibson]

"RPM theorists stop right there. If you have the case capacity and throat dimensions to maintain alignment and can take that bullet on up in pressure until you reach the required velocity level, and your barrel has a harmonic node at that point, then the higher velocity will stabilize a deformed bullet again assuming that it deforms consistently. I find harmonics to be the real limiter here as each barrel is different. Just depends if you want to explore what you have."

Not quite right. Inaccuracy of an unbalanced bullet caused by RPM has absolutely nothing to do with the required velocity for stabilization. Increasing velocity alone will not allow a bullet in flight that has a center of gravity that is not coincidental to the center of form to fly straight. Increasing speed increases the RPM and increases the inaccuracy. It's pretty much that simple.

Most all .22 Hornets have 1-16" or perhaps 1-14" twists. You simply HAVE to push a 50-55 gr bullet fast with those twists to stabilize a bullet of that wieight, no real secret there. With a 16" twist the RPM at 2800 fps is 126,315 which is just inside the RPM threshold and good accuracy with a cast bullet is very feasable. With a 14" twist the RPM is 144,827 which is probably outside the RPM threshold and accuracy may not be good at that high a velocity. However, given a very good cast bullet of correct alloy and well fitted to the throat and a slow powder powder is used (hard to do in a Hornet eh?) then good accuracy is also feasable. Very good accuracy can easily be attained with either twist in the 2400 fps range.

Once the bullet in flight is stablized by an appropriate velocity and rotation it is the unbalances in the bullet that are adversly affected by increased RPM (especially well into or past the RPM threshold) causing inaccuracy. Increasing the velocity past that will not bring accuracy back. Accuracy will only worsen.

Larry Gibson

[45 2.1]

[quote=Larry Gibson;271742 Not quite right. Larry Gibson[/quote]

For that matter, you aren't either. Assumptions are only that until proven otherwise and your interpretation of RPM theory is material dependent. Bass is farther along than you on this, perhaps you might listen closer to some of the things he has said.

[Bullshop]

I may not be remembering correctly but seem to remember about the Bator being designed to be stable at sunsonic velocity from a 1/16" twist.
I do know for sure it works good from my single six 22 Cooper. The Cooper single six is capable of about 1500 fps at full throtle, the same loads going 2000 from a sealed breach. From the single six I shoot them mostly without gas checks with lighter loads at about 900 fps. Assuming the single six as having a 1/16" twist and for iron sighted hand gun range they are working good for me. The federal bulk 22 lr ammo fired from a 5" revolver clocked at 900 fps, for a comparison.
BIC/BS

[felix]

Dan, then the Bator 22 should shoot fine indeed! ... felix

[Yance]

I may not be remembering correctly but seem to remember about the Bator being designed to be stable at sunsonic velocity from a 1/16" twist.

The Bator may be "stable" at low velocities, (makes round holes in paper), but the holes were too far apart out of my 21" Contender. I had to drop back to lyman's 225438 and 2.7 gr W-231 with a WSR primer to approach 1" @ 50 yards. Squirrel huntin' accurate...if the squirrels would cooperate.<G>

TD, give the little Lyman a try.

[mainiac]

Also, as an added tidbit, I have got my very smallest groups,(sub m.o.a.) with lilgun powder,,,,, BUT, i also get extreme fliers with this powder. The 4 shot groups out of 5, might be a .450, but a flyer will open it to 2-2.5 inches. This happens all to often with lilgun, so i am trying to avoid it. Also,this powder gives huge velocity variations,(150 f.p.s. or so). Dont know if this is the culprit, shooting groups and also the chronograph, sometimes the fliers have a normal velocity.Maybe i need to try a primer experiment,with this powder. Lilgun behaves in the same way with every gun that i have shot it in,not just the hornet.

[Bass Ackward]

[QUOTE=Larry Gibson;271742Not quite right. Inaccuracy of an unbalanced bullet caused by RPM has absolutely nothing to do with the required velocity for stabilization. Increasing velocity alone will not allow a bullet in flight that has a center of gravity that is not coincidental to the center of form to fly straight. Increasing speed increases the RPM and increases the inaccuracy. It's pretty much that simple. Larry Gibson[/QUOTE]


Larry,

Let's look at some of this weekends trials.

I have a nose heavy bullet that weights 225 grains in 44 caliber (my design for rifles) that I haven't been able to stabilize at 200 yards in a handgun. I have been trying this bullet for four years at every clip along the velocity chain. Darn thing will just shoot one hole groups at 25 yards but starts to tip at @ 75 and then just goes haywire for three foot groups or worse at 200. To include this weekends trials, this particular load was going 1050 fps doing 37,000 rpm. (20 twist Redhawk) (It's a really poor balance design for low velocity)

Just by coincidence, my rifle load uses that same bullet at 2000 fps. This works out to 37,000 RPM (38 twist rifle) 200 yards with that will just have nice little round holes and some semblance of groups. (5")

37,000 = 37,000. So is it just that simple?

[stocker]

mainiac: I'm following this with considerable interest. This fall I acquired a Sedgely Springfield in 22 hornet. Unfortunately I have yet to start on a stock for it as I was able to get the metal only. Not sure if I'll have time this winter or not as I am up to my ears in checkering jobs.
I'd like to know what primer you are using? An older Ross Seyfried article touted small pistol as giving best results in his experience with Hornets.

[Bass Ackward]

Also, as an added tidbit, I have got my very smallest groups,(sub m.o.a.) with lilgun powder,,,,, BUT, i also get extreme fliers with this powder. The 4 shot groups out of 5, might be a .450, but a flyer will open it to 2-2.5 inches. This happens all to often with lilgun, so i am trying to avoid it. Also,this powder gives huge velocity variations,(150 f.p.s. or so). Dont know if this is the culprit, shooting groups and also the chronograph, sometimes the fliers have a normal velocity.Maybe i need to try a primer experiment,with this powder. Lilgun behaves in the same way with every gun that i have shot it in,not just the hornet.



Same for me. (357 & 44)

I figure that is because it is basically it acts like a non linear powder in the same case. So any slight change in ignition, say because of powder position, and it can cause weird stuff to happen.

[crowbeaner]

You might want to try some 2400 as well. I'm waiting for spring to start load development with my 222 and the 225415. Don't sell those ol Savages short; they shoot as well as anything with the right fodder. A friend has one in 222 and it sort of surprises even me once in awhile. I use Hornady checks exclusively, and seat the check before sizing with the seater insert. If you need a heavier bullet you might look at the RCBS 55 grain. It's my next acquisition in 22 caliber.

[mainiac]

mainiac: I'm following this with considerable interest. This fall I acquired a Sedgely Springfield in 22 hornet. Unfortunately I have yet to start on a stock for it as I was able to get the metal only. Not sure if I'll have time this winter or not as I am up to my ears in checkering jobs.
I'd like to know what primer you are using? An older Ross Seyfried article touted small pistol as giving best results in his experience with Hornets.

When i first started shooting this gun,a farted around and finally found that the sierra 45 gr hornet bullet would shoot m.o.a or a little larger. I then found that the .223 sierra shoots better than the .224, and finally i read where small pistol primers were more accurate in the hornet, and that is for-sure fact with this gun!! I use cci-500 in it exclusively now. Shooting the green box bullets with cci 500 primers, and h-4227 powder, this old gun would easily shoot half-inch groups@ 100! Now i shoot nothing but cast in it, and continue to be amazed how the cast boolit can either shot well,or be a total migraine!!!

[Larry Gibson]

For that matter, you aren't either. Assumptions are only that until proven otherwise and your interpretation of RPM theory is material dependent. Bass is farther along than you on this, perhaps you might listen closer to some of the things he has said.

Matter of opinion. I pay a lot of attention to a lot of things Bass says. How about you offering some proof that RPM does not effect the accuracy of bullets in flight?

Larry Gibson

[stocker]

mainiac: thank you for that. Could save me a lot of time and effort.

[45 2.1]

Matter of opinion.
Yep, everyones seems to have one of those, good or bad.

I pay a lot of attention to a lot of things Bass says.
That hardly shows.

How about you offering some proof that RPM does not effect the accuracy of bullets in flight? Broad subject and you didn't say boolits either. Lots of examples of guns, big and small, that don't have rifling to spin the bullet.

[Larry Gibson]

Larry,

Let's look at some of this weekends trials.

I have a nose heavy bullet that weights 225 grains in 44 caliber (my design for rifles) that I haven't been able to stabilize at 200 yards in a handgun. I have been trying this bullet for four years at every clip along the velocity chain. Darn thing will just shoot one hole groups at 25 yards but starts to tip at @ 75 and then just goes haywire for three foot groups or worse at 200. To include this weekends trials, this particular load was going 1050 fps doing 37,000 rpm. (20 twist Redhawk) (It's a really poor balance design for low velocity)

Just by coincidence, my rifle load uses that same bullet at 2000 fps. This works out to 37,000 RPM (38 twist rifle) 200 yards with that will just have nice little round holes and some semblance of groups. (5")

37,000 = 37,000. So is it just that simple?


Bass

That's apples and oranges and you know it.

Let's talk apples; A bullet does require an initial amount of spin (rpm) to stabilize whether out of the revolver or the rifle. That translates into a minimal velocity to remain stable. Obviously in the revolver (1050 fps) the bullet is stable at 25 yards but the velocity drops below the required velocity for stability at 75 yards. With the rifle's muzzle velocity of 2000 fps the remaining velocity at 200 yards is still above the minimal velocity required to keep the bullet stable, thus it is still accurate. If you drop the velocity of the rifle load down at some point it will exhibit the exact same accuracy at 25 yards and inaccuracy at 75 yards. It will have the required velocity to stabilize the bullet at 25 yards but not at 75 yards. The required velocity will be different than with the revolver because of the rifles slower twist but the result will be the same.

Now let's talk oranges; The RPM threshold has nothing to do with the initial velocity required for stabilization of a specific bullet in a specific twist. The RPM threshold has to do with that area of RPM where the unbalancing defects (center of spin is not coincidental with center of form) are spinning enough to cause increasing inaccuracy. This iswhen the RPM causes increased yaw and pitch in the unbalaced bullet in flight. This causes the inaccuracy. It's that simple.

Larry Gibson

[Bass Ackward]

Bass

That's apples and oranges and you know it.

You wrote, "Increasing velocity alone will not allow a bullet in flight that has a center of gravity that is not coincidental to the center of form to fly straight."

Larry Gibson


Larry,

This was your statement above. I simply sited an example where RPMs were exactly the same and only velocity was different so we would be talking apples to apples.

And in that particular case velocity did stabilize an unbalanced design or form. Unbalanced defined by a poor ballistic design. So I don't think it's as cut and dried as you think.

There are two forms of center that I specifically look at. Yaw is affected by load and bullet design. Ballistic coefficient of that bullet determines how fast it goes to sleep. The better ballistic coefficient something has, the wider the load selection can be for this bullet. Rpms has very little if nothing to do with that type of inaccuracy. In fact, slower velocity can calm a poor BC slug (wide meplat) that is yawing.

Prove it to yourself. Drive down the road at 55 MPH and stick your hand out the window with palm up to indicate a wide meplat. Then angle your hand as if in yaw and feel the force. Then put your hand in the form of a knife edge and repeat. How much force do you feel now? Slow down to 35 and repeat both again. Then ask yourself why cast are easier to achieve accuracy at low velocities?

Rotation of a bullet around it's axis is strictly an RPM issue. What happens to a bullet as far as compression means little from an RPM standpoint if it is uniform and doesn't affect the balance (much) around it's axis. Uniformity comes from pressure in the mold. The mold in this case is your bore. If your bullet is of a uniform density (no air pockets) compression and alignment was straight when it entered, balance should be uniform and even more to the rear now making it easier to stabilize. But in that same mold that barrel is whipping that bullet from side to side as it procedes down that pipe giving it momentum in what ever direction it is traveling. That force is unbalancing and rebalancing that slug as it goes. This is way over simplified just to show how hard a perfect axis is to achieve and why low velocity is the easiest way to shoot cast. But also how harmonics comes into play. And why freefloating isn't best for HV cast as it is one omre variable to be controlled.

That's where the changing center of pressure comes in. C of P is much more difficult for me to understand. C of P is affected by velocity for stability of flight whether an object is rotating or not. (key point) This is what allows something that is nose heavy or back heavy to stabilize. Center of pressure changes (moves) under acceleration and deceleration (as in game) which is what affects stability in game after a bullet is truly mangled and unbalanced. From what I understand, (very complex subject) if the center of pressure is correct for the form, then true balance around the center of axis can be countered. (why rockets fly) OR .... when you reach the correct velocity, you can stabilize something that is unbalanced. Or why a bullet eventually destabilizes at some range.

So .... velocity can counter rotational deformity to a point. This is why breech seating (straight line seating for cast) is ultimately the most accurate form of shooting cast. It achieves as close to perfect rotation around the axis. This removes velocity more from the equation and lower velocity accuracy, which is less affected by ballistic coefficient, is the most accurate way to shoot cast.

Look, in our imperfect alignment style of bullet jumping and slamming, are able to achieve fairly good accuracy being outta balance around the axis as we are. But we have one more chance to correct that. And that is in the mold .... of the bore. And don't kid yourself, you are outta balance rotating around that axis all the time. But somehow you strive to counter that by either less yaw at the beginning or the correct velocity for the new form. So, if I haven't lost you, you can make the right (correct) hardness to achieve the correct bullet form (deformation) for the C of P to work at a harmonic node for your barrel, you can stabilize and have accuracy. Obviously, BC makes this much easier to achieve as it minimizes yaw effect.

Why do supersonic aircraft have pointed noses? What velocity range is ballistic coefficient most critical? Now .... why is cast accuracy easier to achieve at (lower) cast velocities? Still think it's RPMs? :grin:

And .... simple this isn't.

[Larry Gibson]

Bass

You're confusing yourself. The rotational spin (RPM) required for initial stabilization of the bullet is actually quite low but is still dependant on the velocity compared to the twist. Stability of the bullet is not a requirement for accuracy. Bullet stability merely means that it flies point forward. All bullets exibit some degree of yaw and pitch. It is how well we control these along with the consistancy of the load that determines accuracy. Many, many times we can have very stable bullets but an inaccurate load. The RPM threshold is that area of RPM where the inconsistancies and imbalences of the cast bullet are accentuated by the increased RPM of increased velocity and then inaccuracy results. The bullet has already been stable and accurate. The RPM threshold has to do with when the bullet loses that accuracy not stability. Initial stabilization of the bullet has to do with the RPM threshold. A bullet must have sufficient velocity and rotational spin to stabilize and BECOME accurate. Apples and oranges.

I'll further answer some of your last post;

This was your statement above. I simply sited an example where RPMs were exactly the same and only velocity was different so we would be talking apples to apples.

As stated it was the remaining velocity that was the difference between your loads. The rifle load was still going fast enough at 200 yards to remain stable. That was the only difference. Neither load had even approched the RPM threshold so there was no effect from that what so ever.

And in that particular case velocity did stabilize an unbalanced design or form. Unbalanced defined by a poor ballistic design. So I don't think it's as cut and dried as you think.

Quite cut and dried, it has been known for a long time that with a heavy for twist bullet a higher velocity is required to stabilize it. Again, common ballistic information dealing with the initial stabilization of the bullet and nothing to do with the RPM threshold.

There are two forms of center that I specifically look at. Yaw is affected by load and bullet design. Ballistic coefficient of that bullet determines how fast it goes to sleep. The better ballistic coefficient something has, the wider the load selection can be for this bullet. Rpms has very little if nothing to do with that type of inaccuracy. In fact, slower velocity can calm a poor BC slug (wide meplat) that is yawing.

Yaw is effected by far more than "load and bullet design". I've read a lot theories as to why bullets go to sleep and this is the first where BC has been the reason, can you cite your reference so I may read it? Again you are discussing requirements for initial stabilization of the bullet. It has nothing to do with a cast bullet passing through 125,140,000 RPM and MAINTAING accuracy. Let me say that again; the RPM threshold has to do with an ALREADY STABLE AND ACCURATE cast bullet maintaing accuracy beyond 125-140,000 RPM.

Prove it to yourself. Drive down the road at 55 MPH and stick your hand out the window with palm up to indicate a wide meplat. Then angle your hand as if in yaw and feel the force. Then put your hand in the form of a knife edge and repeat. How much force do you feel now? Slow down to 35 and repeat both again. Then ask yourself why cast are easier to achieve accuracy at low velocities?

What does that have to do with cast bullets at or above 125-140,000 RPM? Instead of trying to think of all sorts of obtuse reasons why not and going off on tangents why don't you stick to the point and pay attention to how RPM affects the flight of a cast bullet as it passes through the RPM threshold.

Rotation of a bullet around it's axis is strictly an RPM issue. What happens to a bullet as far as compression means little from an RPM standpoint if it is uniform and doesn't affect the balance (much) around it's axis. Uniformity comes from pressure in the mold. The mold in this case is your bore. If your bullet is of a uniform density (no air pockets) compression and alignment was straight when it entered, balance should be uniform and even more to the rear now making it easier to stabilize. But in that same mold that barrel is whipping that bullet from side to side as it procedes down that pipe giving it momentum in what ever direction it is traveling. That force is unbalancing and rebalancing that slug as it goes. This is way over simplified just to show how hard a perfect axis is to achieve and why low velocity is the easiest way to shoot cast. But also how harmonics comes into play.

Yes that was very much "over simplified" but is exactly why low velocity is the easiest way to shoot cast bullets accurately. The reason is because at low velocity cast bullets stay at or under the RPM threshold. Accuracy is less when we cross a point of the threshold. That is the point Bass and you have just said so. Perhaps you should realise what you are saying.

That's where the changing center of pressure comes in. C of P is much more difficult for me to understand. C of P is affected by velocity for stability of flight whether an object is rotating or not. (key point)

Come on Bass, bullets that do not rotate (spin) are not stable and the design or location of your C of P has nothing to do with it. No spin, no stability.

This is what allows something that is nose heavy or back heavy to stabilize. Center of pressure changes (moves) under acceleration and deceleration (as in game) which is what affects stability in game after a bullet is truly mangled and unbalanced. From what I understand, (very complex subject) if the center of pressure is correct for the form, then true balance around the center of axis can be countered. (why rockets fly) OR .... when you reach the correct velocity, you can stabilize something that is unbalanced. Or why a bullet eventually destabilizes at some range.

No argument there, bullets require a correct velocity given their design and the rate of twist (spin) to stabilize.

So .... velocity can counter rotational deformity to a point. This is why breech seating (straight line seating for cast) is ultimately the most accurate form of shooting cast. It achieves as close to perfect rotation around the axis. This removes velocity more from the equation and lower velocity accuracy, which is less affected by ballistic coefficient, is the most accurate way to shoot cast.

Again correct, breech seating cast bullets is a very good way to try to align the center of form with the center of spin. The closer those two coincide the more accurate a correct bullet (for twist) will be. However Bass, answer me this; how many shooters that breech seat cast bullets shoot them at or above the RPM threshold? Answer is none. So again I have to ask what this has to do with the point here?

Look, in our imperfect alignment style of bullet jumping and slamming, are able to achieve fairly good accuracy being outta balance around the axis as we are. But we have one more chance to correct that. And that is in the mold .... of the bore. And don't kid yourself, you are outta balance rotating around that axis all the time. But somehow you strive to counter that by either less yaw at the beginning or the correct velocity for the new form. So, if I haven't lost you, you can make the right (correct) hardness to achieve the correct bullet form (deformation) for the C of P to work at a harmonic node for your barrel, you can stabilize and have accuracy. Obviously, BC makes this much easier to achieve as it minimizes yaw effect.

Sorry but I'm not sure of your point here. Yes all cast bullets are "rotating around that axis all the time" as you say. That is why at some point in the RPM threshold that imbalance is accentuated by the increased rotational spin of RPM and accuracy decreases. By increasing alloy hardness, using a slower burning powder and having the perfect fit to the leade and bore you can maintain a reasonable degree of accuracy above the threshold but accuracy with that bullet will still be best below or at the RPM threshold. It is just a matter of how much less accuracy one is willing to accept for higher velocity. Point is; accuracy with any cast bullet will be below or at the RPM threshold.

Why do supersonic aircraft have pointed noses?

Supersonic aircraft do not rotate to maintain stability in flight. So what the heck does RPM of bullets in flight have to do with that? You are way off on another tangent.

What velocity range is ballistic coefficient most critical? Now .... why is cast accuracy easier to achieve at (lower) cast velocities?

Cast bullet accuracy is easier to achieve at lower velocities because there is less acceration forces which causes less deforming obturation to unbalance the bullet in flight. Also lower velocity means less RPM to accentuate those imbalances and cause inaccuracy.


Still think it's RPMs? :grin:

Yes I do. Not sure why you are grinning unless you are finally realizing it too.

And .... simple this isn't.

No it is not simple but the fact that there is a RPM threshold with cast bullets is. That is why the cast bullet bench resters use very slow twists. They also use many of the other techniques we've discussed but they know that to shoot cast bullets accuratel at high velocity then they must keep RPMs down. They do that by using slow twists and lighter cast bullets at just fit the neck and leade of the bore. A few are right at the upper end of the RPM threshold but none are beyond it by any means. The RPM threshold is also why you still get better accuracy with you LBT bullet at or below the RPM threshold than you do above it. Granted that bullet does pretty well above the threshold but the point is that LBT bullet still shoots better at or below the RPM threshold just like any other cast bullet. The RPM threshold is real.

Larry Gibson

[Bass Ackward]

Larry,

All you have to do is that one little test I told you. Just run the experiment and think about what you see with your own eyes. Same exact thing happens to a bullet as it hits air. Run it as many times as you need to.

Hints:

1. Your hand position is the BC answer you seek. Wide meplat is palm up, knife edge is spitzer.

2. When you move them up or down, the amount and speed of the movement at both speeds in each position, is the yaw answer you ask for proof of.

3. The results of both of those steps along with the comparrison of the force that moved your hand at the two speeds will show you why cast accuracy is best at the lowest possible velocity that you can stabilize that bullet.

That's external ballistics. No six figure RPM or scary four digit velocity numbers to complicate the issue. It is what it is. And as you like to say, "It really is that simple."

[Larry Gibson]

Bass

I was running that experiment 55 years ago when I was a little kid. However that comparison is pretty much "over the top". It has nothing to do with what we are talking about. Ponder me this; I have 150 gr Speer RN and 170 gr Hornady FN bullets. How come they shoot just as well at 2800 fps as they do at 1500 fps (reduced loads) In the same .308 and '06? Oh that 's jacketed bullets and they are different huh? Well how about a cast bFN bullet out of my Siamese Mauser that shoots just as well at 2100 fps than it does at 1050 fps? Not enough? OK how about 358156 that shoots just as well at 2000 fps as it does at 800 fps out of my .35 Remington? Or 313631 (GC SWC) that shoots just as well at 1800 fps than it does at 800 fps? Your ascertation that RN or FN bullets shoot more accurately at lower velocity has no merit.

All of the above cast bullet loads are below the RPM threshold BTW. The best cast bullet accuracy IS NOT "at the lowest possible velocity that you can stabilize that bullet". You must alos have a consistant load. With many cast bullet/powder combinations you must reach consistant ignition for accuracy also. In many, many instances this is above the velocity required for stabilization of the bullet. That is a fact and you know it. Sometimes with some bullet/powder combinations (light bullet/slow powder) consistant ignition will not happen until the velocity is above the RPM threshold and the bullet/powder combination will not be accurate.

Now then, I shall do as you say and run your experiement this very morning (even though it is cold here in NC). It will not show me anything relevant to this topic but I will do it be cause You have asked. That is the same as I have consistantly done when ask me to try something. How about you do just one of the things I've aked of you? Take your .30 cal LBT and load up 5 shot test groups that will run from 1600 fps to 2600 fps in say 50 - 100 fps increments and test them in that 10" twist '06 of yours. I'll trust that you will shoot your best with each group. Chronograph each test load. We will then see at what velocity, i.e. RPM, that bullet is most accurate. Can you do that?

Larry Gibson