I would much rather work with the medium burn rate powders, like H4895 or IMR4895 or maybe even 4198's on the faster rifle powder side. Yes - in the 6.5x54, they are slower when talking about cast bullets, but these are commonly known as medium burning powders.

Getting a slightly slower start of the bullet, rather than the fast punch of a low density load of the pistol powders, I think it a good idea. A slower building of pressure using these medium powders (4895's, 3031, 4198), and not having to use a filler is also a good thing.

Herculese powder 2400 and IMR or H4227 are VERY fast burning rifle powders (.22 Hornet and similar cases) but also very slow burning pistol powders, at the same time & are more commonly thought of as pistol powders - unless you shoot a Hornet, that is.

2400 was developed as THE Hornet powder as it was used to develop 2,400fps - back in the 1920/1930's in the .22Hornet.

They are both good at developing top-end loads in magnum handgun ctgs. like the .44 mag and .357 mag.