I am certainly no expert on where the CG is located in the various bullets that are commercialy available. I'll make a stab at it and hopefull ALF or someone more knowledgable than me will correct me where I am wrong in the following answer to your question.

Intuitively though, if a bullet has more bullet mass to the rear of it's center point (on the longitudinal axis) then it will be tail heavy. If the opposite is true then it will be nose heavy thus closer to dart shape. If we drop a tail heavy bullet then we would expect it to fall tail first and the opposite if nose heavy.

I don't know if bullet manufacturers look at where he CGs of their bullets are or whether they consider it in bullet design.

It would be an interesting experiment to locate the CG for various designs. Looking at the pic you posted of the Barnes Banded FP solid and with the assumption that the density of the metal in the bullet is uniform, then two factors will push the CG towards the rear of the center line of the bullet. The first is the taper of bullet from it's flat point to it's maximum diameter. The second would be the amount of mass in the bands at the rear of the bullet. This would be additive as this is the portion of the bullet with the greatest diameter. If the bullet was designed with driving bands instead of wide bands then there would be less mass in the maximum diameter portion of the bullet and the CG would be moved forward. How much the CG would be moved, I don't know.

465H&H

When I was in the middle of my rudimentary penetration tests a few years back, I tried manipulating the CG of the old style Barnes RN monos (500gr .458).

Before modifying any bullets, I tried to measure the ratio of nose to base weight by bridging the bullet first with the nose on a sensitive scale and base on a knife edge as near the base as I could manage and then reversing the bullet. This was not easy to do but it did manage yeild repeatability and sensitivity to modifications. For the unmodified Barnes, my records indicate that the nose contains approximately 49% of the mass in front of center of form and the base 51% for a ratio of .961. This percentage ratio taken over the oal of 1.535" of the bullet put the CG at 0.782" rearward of the nose (or 0.753" forward of the base).

These results may well be outside the tolerance of my measurement technique so I tried five individual modifications with two methods. For the first modification, I cut grooves around the barrel groove diameter portion of two bullets with the grooves large enough per my mass per volume removed calculations to move the CG forward of CF. I also center drilled the base of three slugs as the grooves removed a significant portion of the bearing surface.

Bullet "A" had 3/16"x.250" deep basal cavity which removed 1.00 gram and brought the nose/base ratio to .979 (per measurement)
Bullet "B" had 3/16"x.350" deep basal cavity which removed 1.42 grams and brought the nose/base ratio to .990 (per measurement)
Bullet "C" had 3/16"x.550" deep basal cavity which removed 2.24 grams and brought the nose/base ratio to .993 (per measurement)

Bullet "D" had three grooves .100"long x .020" deep turned off base, each groove .100" apart: nose/base ratio .977 (per measurement)
Bullet "E" had same as "D" but grooves were .040" deep. . . . . . . . . . . . . . . . . . . : nose/base ratio .994 (per measurement)

Upon firing, what I discovered was:

All of the bullets with the basal cavities exited my 24"x24" recording footprint within 3' depth of penetration and exibited wild precessing the whole way. Bullets "B" and "C" caused EXCESSIVE PRESSURE!!! This was unexpected but obvious upon reflection. The bullets must have been upsetting like Minie' balls and increasing bore friction. However, I do not know why they did not penetrate any straighter than an unmodified slug.

As for the grooved bullets, bullet "D" penetrated off course so badly that it did not print at 2' depth, even within a 24" square! Bullet "E" faired a little better but was fully sideways as evident by keyhole in plywood recording slat at 2' and was recovered in recording slat at 4', imbedded sideways. There is no good rifling engravement on the recovered bullet and I've subsequently learned the bore of that rifle is oversized so this test result was also fraught with other problems.

So, what did I learn from my CG vs. CF tests? Don't drill holes in the base as they can cause very sticky bolt lift and attendent indicators of overpressure and bullets require a certain minimum of rifling purchase. In my penetration tests of solids (which included velocities, nose profiles, bullet construction, and weight distribution, the single decisive factor that gave dependable straight line penetration in saltwater was a flat nose.

/

Several posts have stated the bullets tumble when they slow down enough to lose stability. Is there any way to measure or to predict when this destabilization occurs? It seems to me that if it occurs in the last two or three inches of penetration then it's importance may be minimal. If destabilization and the resultant tumbling occurs right after entry then it could be a severe problem.

465H&H

/

ALF

Can you give us some examples for nondeforming solids?

465H&H

/

I just measured some Woodleigh soilds that I have on hand to determine the CG. I balanced the bulets on a knife edge and marked the balance point by pressing down on the bullet and slightly scoring the bullet jacket. Not easy to do but the results were usefully repeatable. Results:

Woodleigh 500 grain, .474 dia. solid.

Total length = 1.330
Dist. of CG to base = .610
Dist. of CG to nose = .720
The CG was 4.1% of the total bullet length behind the mid-point of the length.

Woodleigh 480 grain, .468 dia solid

Total length = 1.319
Dist. of CG to base = .610
Dist. of CG to nose = .710
The CG was 3.7% of the total bullet length behind the mid-point of the length.

Woodleigh 550 grain. .458 solid

Total length = 1.502
Dist. of CG to base = .836
Dist. of CG to nose = .710
The CG was 2.7% of the total bullet length forward of the mid-point of the length.

465H&H

/

Yaw, After having read all the posts,why am I no less confused than when I made that first statement??

Do they yaw at 10 yards or not? and if so were the old timers right in that it changed the true course of the bullet?

Join the club Ray. Still, IF they indeed yaw, are they still tracking straight while in air, and if so or no how do they get back on zero as some have reported them being more accurate at 200 than 100.

As for big game, the 1 or 2 degrees mentioned would surely be negated or worsened by the "angle of attack" on hiting certain surfaces of the animal?
And, so what's the choice? does anyone usually sneak up to 10yards of DG, and then should they then sneak back a bit. Or outrun a charge until gaining by at least 25yards.?
Just let'em have it I reckon.

Pondoro Taylor had many close-range encounters with the old fashioned FMJ round-nosed bullets. I guess for elephant in the jesse he used mostly his favourite 465 NE.

Warrior

quote:

Originally posted by Warrior:
Pondoro Taylor had many close-range encounters with the old fashioned FMJ round-nosed bullets. I guess for elephant in the jesse he used mostly his favourite 465 NE.

Warrior

He killed most of his elephants with a 450 NE No2. Still, he prefered H&H rifles for their generally lower weight.

JPK

JPK,

Sure. The point I was getting at was actually that the round-nosed FMJ bullets were the only ones available to him. He shot thousands and my guess is since he was a poacher he shot most at close range, and he was successful most of the time - that makes me wonder who serious yawing really is. He did say though that he likes the bullet of the 465 NE better with its parralel sides than those that taper more.

Warrior

quote:

Originally posted by boom stick:
jim, you speak "jesse jackson" quite well...

quote:

Originally posted by Warrior:
JPK,

He did say though that he likes the bullet of the 465 NE better with its parralel sides than those that taper more.
Warrior

Yes, and those of the 450NE's and almost all other NE cartridges. as well. The bullets he did not favor were those for the 470, which had a more pointed profile and were not as hemishereical as the others. He found that they had a greater tendency to curve while penetrating.

Maybe it was, as 465H&H has noted, that the pointier 470 bullets had their center of gravity too far back.

For more success with hemisherical round nose solids look to Ron Thomson and Richard Harland, two Zim cull hunters who had near 10,000 elephants between them using the 458wm and hemisherical Winchester solids.

JPK

Too bad Mickey1 cannot further participate in this thread that he started because he was banned from AR.

quote:

Originally posted by 500grains:
Too bad Mickey1 cannot further participate in this thread that he started because he was banned from AR.

That is a crying shame.
Mickey added a lot around here.
What did he do to deserve that?

Yea, what the heck did he do to get banned?

Why waste so much time on something 'of negligible consequence'?

quote:

Data from ballistics studies 10, 13, 14) show quite clearly that:

* Bullets fired from a properly designed rifle yaw no more than a few degrees in flight, regardless of velocity.
* In their path through tissue, all nondeforming pointed bullets, and some round-nosed ones, yaw to 180 degrees, ending their path traveling base forward (Figs 3 and 5).

Thus bullet yaw in tissue, an important consideration, has been confused with bullet yaw in flight, which is, in most cases, of negligible consequence.

Read what M L Fackler has to say about it.

quote:

Originally posted by Jagter:
Why waste so much time on something 'of negligible consequence'?

That's why Mickey1 got banned.