I ran Cast Performance Bullet Co. and in the early 90s we did a LOT of testing, not only of our bullets but also of every other bullet we could. It was very interesting and fun as well.
"Cup-and-Core" bullets are all made from 2 components, the jacket, made from materiel called "strip" and the lead core alloy.
Strip was made by Kennecott and Alcoa and could be ordered in various alloys of gilding metal (Copper/Zink alloy) and rolled onto a spool as a long strip (hummmm wonder why they call it that
The lead cores are made from alloyed metal too with lead and tin being the 2 metals used in all, and some having a small % of Antimony also.
Strip is used for certain bullets at certain thicknesses. As an example, Hornady used to use the same strip for bullets from the 130 gr 270 to the 225 grain 338. (if my memory is correct)
So you can see that all would have the same thickness of jacket at the shank, but the .277 would have a thicker jacket in comparison to it's diameter. If that strip was .022" (as an example only) you would have a total shank diameter of .044" in jacket and .233" in lead. So the jacket will comprise close to 15% of the thickness of the bullet shank. But step up to a .338 you still have only .044" of jacket and the other .294" is lead. that means the 338 bullet would have a shank thickness of jacket to lead of about 12% jacket and 88% lead. So jacket thickness should be increased to get thicker as the bullets get larger in diameter, but it can't be done for every bullet and every weight of bullet, as the cost of the tooling would be prohibitive. Every bullet would have to be made on a dedicated set of cupping dies for every diameter and every different weight to be perfect. None of us could afford the bullets if any company did that because of the cost of tooling.
So they take averages. Most generally, Hornady did well in it's averages in their old Inner-Lock line. Not all, but most I have tried were good enough and some are very good. The ones I have seen that were sub-standard to my way of thinking were in fact the 338s they make, because their jackets were too thin for the diameter of the bullets and that causes them to break up badly and not penetrate well.
The thinner the strip, the easier it is to make the jackets accurate and even. But the thicker the jacket the more force is needed to form it, and the more likely "memory" of the metal is to cause slight differences in the cups.
The ideal cup and core big game bullet has a jacket of 25% to 30% of it's diameter at the 3/4 point up it's shank, and going down to the base. From that 3/4 point, (from base to 3/4 ways up the shank) it should taper evenly in thickness to the tip with the jacket being only .004 to .007" at the tip
That's the ideal, but it doesn't exist in industry for the reasons above.
In effect a 243 bullet should have a jacket at the shank of ..031 to .040
A 257 should have .032 to .043
A 264 should have a shank jacket thickness of .033 to .044
A 277 should have a shank jacket thickness of .035 to .046
A 284 should have a shank jacket thickness of .035 to .047
A 308 Should have a shank jacket thickness of between .038 and .051
And so on and so on.....and the reason for the different thicknesses is the proposed striking velocity of the bullets. so faster round should be thicker then a slower round and so on and so on. All of which taper to a thickness of thin paper at the nose and thicken to that point 3/4 up the shank of the bullet to full thickness.
Now if you think....just imagine how many different dies and tapering swedes there would have to be in a bullet makers factory to do this and get it all the that theoretical ideal.
It is not going to happen in industry as we have it today.
I think the old Remington Core-Lokt, Winchester Power Points and many of the Hornady Inner-Lock bullets are about as good as we have seen in the past, and going up to today, for cup and core bullets. Only a custom shop can make the "ideal" bullets and the cost would be higher than most of us could pay. If a bullet is good enough to work, kill well, even if it's not ideal, no one is going to pay a super high price for something better that doesn't offer some real world advantage. If Speer and Sierra would simply double their strip thickness on their hunting bullets it would help them a lot, but bullet companies don't really want to know what we'd like. They only want to know what we'll accept and pay for. They advertise accuracy as the mecca of bullet n design and it's not for any bullet but varmint and target bullets, but the average American shooter has accepted this marketing ploy.
For me, I'll take a good hunting bullet that expands and doesn't loose more then about 45% of it's weight that holds 1.25 MOA every time over a bullet that sheds 70-85% of it's weight even if that bullet shoots one hole. I have never shot at an animal or man ever that was smaller than 1.25 MOA. I want 1/3 to 1/8 MOA for target bullets and varmint bullets but for big game I want good performance, and about anything under 1.5 MOA is just fine.
OK....rabbit trail followed --------------- no rabbit here...
