best powder for cast v jacket. Why not same

[nelsonted1]

This is a very basic question, I've known that since I was a grasshopper (or weevil). By that I mean, like, why? I can't even qualify the question. I know what not to use but I have no clue as for why.

Ted

[winelover]

For handguns cartridges I use 2400 for both cast and jacketed with equal results!

Winelover

[theperfessor]

In a lot of pistol rounds the powders are the same for both, although there will probably be a slight difference in charge weight. In some older, non-magnum rifle rounds the powders are the same for both also.

In larger capacity rifle cartridges, generally cast bullets are shot at lower velocities than jacketed and therefore you need less oomph and have to deal with the unfilled case volume in some way - such as switching to a bulkier powder and/or using inert filler materials. There is also the question of pressure rise time and bullet deformation from the pressure impact and stripping of a cast bullet at the rifling, something of little or no concern with most jacketed slugs.

[Maven]

Ted, As you know, CB's and jacketed bullets can't be driven to the same velocity and pressure levels and still maintain pinpoint, or rather, m.o.a. accuracy. Thus, to get optimum results with a jacketed bullet requires a powder with different characteristics and in different amounts than one used with CB's. However, there is some overlap so that IMR 3031 and IMR 4064, for example, can be used with either projectile in the .30-06, albeit with different charges. Milsurp IMR 7383 and WC 860 can also be used with both types of bullets, so can black powder for that matter.

[1Shirt]

Like Mavin says, there are overlaps in both handgun and rifle, but the big difference (to me at least is case vol). Small pistol vol compared to larger vol in rifle cases. He used 4064 and 3031 in O6 brass and I agree. The second vol of the Lee Reloading manual has a section on just this specific subject with rifle powders (so called) and cast loads. Note also that powder like 4759 depending on which rifle ctg. has both multi jacketed and cast capacity. I use it for both in 375-H&H for practice loads with good results.
Good luck.
1Shirt!

[lwknight]

Some powders just work best at high pressure loads and powders that work good at lower pressure loads tend to get more radical at higher pressures.
in a perfect scenario , the powder would ignite and apply X pressure to the bullet and increase in burn rate to maintain the same pressure as the bullet accelerates for the entire length of the barrel to gain maximun velocity and accuracy.
It sounds great in theory but, in real life we have to work a balance to get the best than we can for given case capacity , bullet weight, bullet sectional density , gun pressure tolerance , bullet pressure tolerance , gunpowder reactivity to different pressures and burn rates.
Pistols are more simple than rifles so more powder choices overlap.

[MT Gianni]

The short answer is you can slap or even spank a jacketed bullet but a cast needs to be pushed.