MontanaRifleman
Well-Known Member
I'm not a ballistics expert, but I'm not so sure that a bullet will increase in gyroscopic stability to be "stable enough" for terminal stability at long range.
CEB 140grn G10 MTH & 6.5 WSM-
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I'm not a ballistics expert, but I'm not so sure that a bullet will increase in gyroscopic stability to be "stable enough" for terminal stability at long range.
Broz
Well-Known Member
From what I remember on this, Joel said they were killing ok, but for some reason my memory is he was not all that impressed. Plus I believe he is still shooting SMK's today. I hope he drops in and corrects that if I am wrong. I will guess that at 1300 yards Joel's impact velocity would be some where in the neighborhood of 1900 fps.
Jeff
Jeff
MontanaRifleman
Well-Known Member
Jeff, if you check out the thread, Joel said "they were no better or no worse" than the SMK's.
I would guess that if he didn't see any advantage about the CEB's over the SMK's he would probably stick with the SMK's for cost reasons. I feel the same way. My current two bullet choices are Bergers and CEB's. Accuracy and terminal performance at long range will be the determining factor for a fianl choice. If the more costly bullet shows no advantage over the other, I'll pick the less costly.
I would guess that if he didn't see any advantage about the CEB's over the SMK's he would probably stick with the SMK's for cost reasons. I feel the same way. My current two bullet choices are Bergers and CEB's. Accuracy and terminal performance at long range will be the determining factor for a fianl choice. If the more costly bullet shows no advantage over the other, I'll pick the less costly.
bigngreen
Well-Known Member
I think that maybe putting this bullet into a media that would provide more hydraulic action in the tip may result in something different, pilling this bullet into a board may just turn it into a solid because of tip damage. With the cup and core bullets the bullets can break in half or collapse exposing softer material that will expand but with mono bullets we don't have any back up if that nose does not open which in my mind make the method of how expantion starts much more critical.
The impact velocity was calculated with a .306 G7 BC so it could be lower but not below 1800 fps for sure, many long rang bullets will open at that velocity and that is why I'm interested in the CEB, it has many characteristics of a long range bullet but it must open at that 1800 FPS mark or it is really only suitable for standard hunting ranges.
I think the 6.5 cal can be a hard size to get what you want, you have a narrow frontal area combined with a long straight bullet, even some of the more frangible bullets in other cals seem to hold together better in the 6.5, I would expect a 338 bullet to initiate expantion easier with the addition of a huge frontal are. When testing bullets it a bad assumption that one cal reacting in one way is an indicator that all of them will react the same, sometimes you need to tweak something because the forces on the bullet has change enough to need a design mod.
Hopefully no one takes my post as the bullet is scrap, it just needs to be modified or the test needs modified or maybe we just flat went beyond this particular bullets capability but shooting and reporting then hashing it out is the only means we make gains in knowledge.
The impact velocity was calculated with a .306 G7 BC so it could be lower but not below 1800 fps for sure, many long rang bullets will open at that velocity and that is why I'm interested in the CEB, it has many characteristics of a long range bullet but it must open at that 1800 FPS mark or it is really only suitable for standard hunting ranges.
I think the 6.5 cal can be a hard size to get what you want, you have a narrow frontal area combined with a long straight bullet, even some of the more frangible bullets in other cals seem to hold together better in the 6.5, I would expect a 338 bullet to initiate expantion easier with the addition of a huge frontal are. When testing bullets it a bad assumption that one cal reacting in one way is an indicator that all of them will react the same, sometimes you need to tweak something because the forces on the bullet has change enough to need a design mod.
Hopefully no one takes my post as the bullet is scrap, it just needs to be modified or the test needs modified or maybe we just flat went beyond this particular bullets capability but shooting and reporting then hashing it out is the only means we make gains in knowledge.
Outlaw6.0
Well-Known Member
BNG, I couldn't agree more. Knowledge is the key to driving this sport forward. I also agree that hydraulic action is a critical function with the CEB's. A test medium other than pine
really has my attention. If they fail, so be it but I would like to see the results.t
I can't comment on "stable enough", that depends too much on bullet design and the dynamic stability implications of the specific design, which can't be good in case of the CEB, since they are awfuly long. Thus center of gravity and center of pressure have to be quite a bit apart, which makes it easy to overturn them (a general issue with extremely long bullets, not particularly the CEB designs).
On the increase I can comment though. Since velocity of the bullets forward motion is the main source of disruption of the bullet tip's ability to maintain a course parallel to the bullets flight path and S(g) is an indicator of the latter ability, a decrease in velocity has to result in an increase in S(g), if everything else stays the same, right?
The bullets rotation is the bullet tip's main factor in maintaining a parallel course to the bullet's flight path, it dampens out the pitching and yawing motions induced by air resistance due to the bullet's (minimally) asymetric form and imperfect center of gravity. If the rotational velocity decreases proportionally slower than the bullets forward motion, S(g) has still to increase, right?
The rotational velocity does decrease slower because the resistance it meets is just the surface friction of the surrounding air, the bullets body does not have to displace air to keep rotating. The bullet's tip otherwise has to displace air, usualy that much, that the air can't be compressed and pushed to the sides directly in front of the tip anymore, but is accelerated itself and has to be pushed in the direction of the bullet's motion.
In "Bullets - Complete Edition" by Beat P. Kneubuehl PhD, it is stated on page 104 that the S(g) of the 147gr Nato FMJ bullet is 1.37 at the muzzle and 2.29 at 300m. A 67% increase in 300m. I hope these numbers are enough to show the magnitude of S(g) increase in flight. If you compare the hypothetical S(g) of a Nosler Accubond fired by a short range hunter at a white tail 150m in distance out of some factory rifle, to the hypothetical S(g) a marginally stable (S(g)>1<1.4) longrange bullet has at 900m, I guess it's plain that the latter's S(g) at impact has to be way higher than the Accubond's S(g) at impact.
The Accubond (or any other stable (S(g)~1.4 at muzzle) hunting bullet) will usually stay stable at these ranges when penetrating the target. If the ability to stay stable after impact into and during penetration of a target medium depended mainly on the projectiles (S(g) at impact, the long range bullet would have to stay stable inside the target medium, too.
So what I wanted to convey all along is, that the rifle's twist doesn't have a great impact on a bullet's specific terminal ballistic at long range since the bullet has already gone to sleep, as long the bullet is launched with an S(g) sufficient to keep it from keyholing at short range. At short range a S(g)>1.(4@the muzzle) is more important because you want the bullet to go to sleep as fast as possible to make sure it impacts point first without yawing and pitching alot, which could screw up the bullets terminal ballistic behaviour.
I hope this wish-wash is readable, makes sense and can give you a picture of my understanding of long range terminal ballistics. Please take into account that English isn't my native tounge.
MontanaRifleman
Well-Known Member
Your English is very good and thank you for your thoughtful reply. After your reply I did some searching.
There is no doubt in my mind the 140 gr bullet pictured by BnG was unstable. Stable bullets do not get bent into bananas. That said, my reasonig that the non-stabilization caused the bullet not to open was wrong. It is the other way around. The bullet not opening was the cause for the non-stabilization. Here is a video that does a good job of explaining.
So, in short, the spin or rotation of the bullet is insufficient to maintain stabilization in a denser medium than air. The expansion of the bullet and the dynamics resulting from expansion maintain the bullets stability.
Here's a good LRH thread discussing twist, spin and terminal velocity.
http://www.longrangehunting.com/forums/f19/bullet-spin-performance-36927/
here's a good QnA on the subject on the GS Bullets site,
GS CUSTOM BULLETS - Twist Rates and Bullet Length
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MontanaRifleman
Well-Known Member
Thanks, the video is great.
Tumbling and forming the banana shape we saw, happens quite often with the rigid models of military fmj. It can be a good means of decreasing sd to maximise energy output inside the target medium without having the bullet disintegrate (libtard interpretations of the hague convention &c). Problem is though, that you have very long narrow channels in most cases. The wound caverty occurs not until half or nearly all of the target is penetrated, especially with small framed game in the 100# area.
It would be nice to see some tests of the 140gr CEB in a more realistic test medium like ballistic gelatine or soaked newspaper. Maybe then we will see some expansion.
MontanaRifleman
Well-Known Member
Well, I finally got out and shot some 143 MTAC's out of the 8" twist 6.5 WSM. Didn't quite stabilize as you can see in the pic. 2 out of 5 did stabilize, but the ain't good enough
Rhian, I've got 45 left over if you want them, otherwise I'll ship them back to Cutting Edge. They are exactley the same dimensions as the 140 MTH's, just no HP drilled into them. They would probably make a good coyote or wolf bullet for good pelts. A wuff or two might run off a ways and not get found... oh well
This was pressure testing load development. Velocities were pretty good with RL33. Elevation was 4000', baro 5 miles away at Three Forks was 30.12 and temp was 23.
Rhian, I've got 45 left over if you want them, otherwise I'll ship them back to Cutting Edge. They are exactley the same dimensions as the 140 MTH's, just no HP drilled into them. They would probably make a good coyote or wolf bullet for good pelts. A wuff or two might run off a ways and not get found... oh well
This was pressure testing load development. Velocities were pretty good with RL33. Elevation was 4000', baro 5 miles away at Three Forks was 30.12 and temp was 23.
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bigngreen
Well-Known Member
Huh, that sucks they did not stabilize! I let my bro in law shoot up the last 140's I had loaded in the 6.5 SS today and they shot amazing, after this hunting season all I need is a range with them cause I know the bullet is landing where I'm dialed I'm very confident with this bullet as far as accuracy, terminal performance is what you'd expect from a copper bullet which I'm going to have to decide before next season if that is something I can live with!
Thanks for the bullet offer but I honestly would not have a need for them in there pointy form.
What stability factor were you at?
Thanks for the bullet offer but I honestly would not have a need for them in there pointy form.
What stability factor were you at?
MontanaRifleman
Well-Known Member
Using the Berger calc, it shows anywhere from 1.42 to 1.46, depending on velocity. It seems obvious that calc is not accurate for copper monometals. I'm guessing you are on the ragged edge of stability, being a little higher in elevation.
2 of mine stabilized and 3 didn't.
