Hi Hicks and Groper, The twist rate factors and related issues you have described are true and well founded. That said, there is a factor that is not considered in these equations, the problem of bullet jump and bullet to bore alignment.
A 7mm RUM for example, has 400 thou jump with the VLD. After ignition, the bullet leaves the case and enters the slightly oversize freebore, travels through this void, then finally engages the rifling. In some instances, the projectile does not engage the rifling in a square, or atleast uniform manner, resulting in a degree of bullet deformation, as well as yaw. In such instances, the more twist rate is increased, the worse the yaw. I believe this is why Weatherby used a 1:10 twist for their 7mm cartridge for so many years.
In the example of the 7mm RUM given, increasing velocity will not increase stability, it will increase yaw. But increasing twist rate will also induce further yaw. What Remington engineers hope, when using the slow twist in the RUM, is that all the factors will work together to produce desirable accuracy. So, we arrive at a point where in this case, we should be atleast entertaining the idea that there was another flaw in the particular rifle in question.
The 7mm Remington Magnum is different again. The cartridge is designed with minimum freebore (unless it is custom throated) while most rifles have a generous magazine box, allowing the user to seat bullets close to the lands. Nevertheless, in high velocity cartridge loadings, any imperfections in the concentricity of the hand load (such as case neck uniformity), will potentially cause yaw. Increases in twist rate magnify the problem.
My original point was, which looking back, I believe I did a bad job of explaining and it was poorly qualified, is that in the 7mm remington magnum and similar or higher power cartridges, increases in twist rate do not always produce desirable outcomes and are not nearly as forgiving as say the 7mm08.
All too often, we blame poor accuracy on the wrong variable. Again using the 1:9 1/4 twist 7mm Rem Mag as an example, these rifles are pretty much bread and butter for my wife and I, we accurize these for clients regularly. Across the board, the 180gr VLD shoots well in these rifles, often around .3" sometimes around .5" which is excellent. Ok so lets say that I receive a Sendero rifle one day that shoots .75" with the VLD after tricking it up. Can I blame twist rate when all of the other rifles shot .3 to .5"? Ofcourse not.
The bottom line, atleast to me, is that as long as we don't understand some of these more subtle problems and instead (in this instance), adopt increased twist rates, we are only adding pressure to companies like Berger who ultimately, will have to continue to toughen up their bullets to counter problems we are creating.
Ok, I hope I have explained things in a useful way, perhaps help people see this particular issue from a different angle (or is it- oh crap, yet another variable! gun))
AZShooter, I would anticiapate that the new .338 VLD's will work well on game weighing 200lb and above. On lighter game, results may be dependent on whether the bullet strikes major muscles and bones. On rear lung shots, the results may be inconsistent and sometimes disappointing. Time will tell. I need to keep up with the play so I will do some testing in due course. A lot of people consider the .338 to be a large game only caliber and for these guys, a tougher jacket will be acceptable. If the bullets are tough, it will be a problem for the guys who simply enjoy the .338 and want to use it on everything.
