300 grain and above can be marginally stable with 1/38 twist, no problem with 1/20, and there is no need to even try something like the 405 grain Beartooth, which is quite stable with the 1/20 twist.
Velocity begins to play a very important part of stability, which will limit how wide a range of velocities you can load the rifle to. Things must be pretty much balls to the walls with the heavier projectiles (300 to 355 grains).
Even if my original intention is to load a .444 at 2200 to 2300 fps with a 240 grain bullet, I prefer the option of having the ability to play with the heavier bullets.
If you're a fan of 1/38, that's fine, but you're leaving potential performance on the table.
