Twist rates and bullet weights

[Jim Watson]

Might be bigger than today's modern high power targets, but not bigger than today's Creedmoor style match targets. These modern versions of Creedmoor matches stress authenticity, and require targets to be the same sizes as were used in 1874 matches.

OK, I was just going by what Kenny Wasserburger said on the Shiloh board. He discussed BPCR LR shooting on the NRA 1000 yard High Power target. He said the 1876 75/75 overlaid on a decimal target would score 140/150.

Are your 1874 style targets the square bull design?

Me? The longest range I have shot BPCR Target is 600 yards, 500 metres on MS

 

[Varminterror]

I don't really understand why you continue to change this to compare modern rifles and cartridges

Because you brought up something absolutely irrelevant to the OP’s question and for some reason you find a need to continue to blather on and on about it… the 72 folks in the world still shooting BPCR care about it, nobody else really does, because it no longer bears importance to the continued evolution of long range shooting…

 

[DMW1116]

You're missing my point also. Since I wasn't asking about comparing old .45 and .44 Black powder cartridges to modern 6mm or .30 caliber cartridges. I was referring to identical cartridges used then, and now; not larger then to smaller now.

Ok what about the results of the more modern twist rates. Are the newer twist rates shooting better than the older ones?

 

[lysanderxiii]

Contextually, this statement is internally contradictory.

Married with Children theme song plays: “You can’t have one without the OTHer…”

When we pick a more aerodynamic bullet for a given cartridge, a given caliber, we’re almost inherently choosing both a heavier AND longer bullet, which also has a longer lever arm between CoP and CoG. For MOST shooters, they just recognize the choice as picking a heavier bullet, even though they are really choosing a more aerodynamic bullet…

We don’t have an infinite number of combinations of ogive profiles, boattail angles and lengths, and bearing surface lengths or material densities available on the market. We can see SOME deviations within this relationship, for example, changing bullet class from a lead core to a mono-metal, or flat base to boattail, and a few outliers like examining Service Rifle bullets with stubby ogives and low BC’s against non-SR bullets which have room for longer ogives, OR sticking a polymer tip out front which adds a lot of length but proportionately less weight - but typically, within the context of a given application and a given aerodynamic demand, we really don’t have that control. If we seek a more aerodynamic bullet, then we inevitably apply a heavier bullet for a given cartridge, and we’re generally accepting it will also be longer, and have a longer moment arm, and demand a faster twist to stabilize.

Maybe unwittingly, most shooters will see that choice not as picking better aerodynamics, but rather as picking a heavier bullet. Folks move from 243win with a slow twist to 6 creed with a faster twist because they “can shoot heavier bullets.” Why? Because they want “more aerodynamic bullets”, not really because they want “heavier bullets.”

Also not surprisingly, when we want even better aerodynamics and we remove the bound of using the same caliber, we again choose a heavier bullet by going up in caliber, which also means an even longer bullet, BUT acknowledging, this choice often does not require any faster spin rate because the proportionality for CoP vs. CoG can be (relatively) retained - again, because we can’t choose infinitely different bullet profiles or substrates.

But in general, “more aerodynamic” is coupled to an interdependency of “heavier” and “longer.”

And, that is why the APPROXIMATIONS, such as the Greenhill formula, work.

When you start to try and apply it to things like solid armor piercing versus HE shells, it starts to fall apart.

It is not contradictory. You are just limiting yourself to small caliber projectiles with very little variation in density (even lead core vs solid copper). Even with these, is you start to stray off in to odd-ball special purpose projectiles, say a tungsten penetrator core in an aluminum carrier, things go awry.