OKbow87, here's some things to consider.
When a crooked bullet's shot out of the case into the rifling, it will straighten up a little bit but not all the way. It's softer than the barrel so it's going to be a tiny bit deformed as it straightens up. So it'll be a tiny bit crooked going down the barrel. Crooked bullets don't hurt the barrel as they go through them. When it leaves the barrel, its slight imbalance makes it jump a tiny bit sideways due to centrifugal force and take a direction not quite perfectly aligned with the bore. These bullets leaving at slight angles to the bore fan out and make large groups at the target.
If the bullet's pretty straight when it leaves the case it'll get really straight as it enters the bore so it's not deformed and goes down the barrel very straight and leaves that way, too. It goes out the barrel very straight and a bunch of these straight bullets cluster at the target in a very small group. And that makes us very happy.
I don't think it's your RCBS dies that's the problem. Most often the cause of crooked bullet seating is related to the cases. If the neck wall thickness isn't the same all the way around, when the sized down case neck comes back down over the expander ball its inside centers on the expander ball and the uneven thickness lets it bend more to the thin side as the ball comes up through it. It helps if the fired case mouth is passed over a spinning bore brush to clean out the powder residue and smooth up the brass, too. Bullets tend to seat and align themselves with the case neck; if the neck's crooked after sizing the fired case, the bullet's going to be seated well aligned with the case neck so it'll be crooked to the case axis just like the neck is.
I suggest having the die's neck lapped out to about .003- to .002-inch smaller than a loaded round's smallest neck diameter. I'd start at .003-inch smaller then if the neck's are a bit tight, lap the die out a bit more to only .002-inch smaller. Any gunsmith worth his shoestrings should be able to do this. Then replace the 25 caliber expander ball with a 24 caliber one.
Or buy a full-lenght sizing using a bushing with the correct diameter. The Redding Type S Full-Length Bushing Die is available for the .257 Wby. Mag.; see it at:
Using your lapped out die or a full-length bushing die will make full-length sized cases have much straighter necks. One can see how crooked seated bullets are by laying the loaded round in a V-block then spinning it with your fingers while looking at the tip of the bullet. Use a magnifying glass to get a better view. An example of what's available commercially is shown at:
As the round's spun in the V-block, the bullet's tip will move about exactly like a poorly passed football. Its tip will enscribe a circle; the smaller that circle is the straighter the bullet's seated. If a dial indicator is mounted on the V-block and placed near the bullet's tip, the crookedness, or runout can be measured. The maximum runout acceptable for good accuracy is about .003-inch.