[MikeG]

Yes - it will work just fine.

The expander plug in my set (also RCBS carbide) measures .426" in the 'straight' section, so this should give you a nice tight grip on the bullet, if you don't flare the case mouth any more than necessary.

The seater will work also, even though it should be flat all the way across for best results.  What you might see is a slight ring around the nose of the bullet, if the seater is not modified.  Doesn't hurt anything, really.

I'd personally file off around the edge of the seater plug, to make the bullet only contact the flat spot in the center (which is of course what I did).  I also prefer the Lyman "M" die for expanding case necks, as it leaves a little 'step' on the inside of the case mouth which helps start bullets straight.  But what you have should get you started OK.

Last advice - seat and crimp in two steps.  A little more work but well worth it, in my opinion.

 

[MikeG]

The lead bullets will be even 'tighter' due to their being 0.002" or so larger in diameter than jacketed.  May have to adjust the expander just slightly deeper OR put a light chamfer on the case mouth to keep from shaving lead from the sides of the bullet.

If you do it right, on the cast bullets you should be able to see where the grease grooves in the bullet are, underneath the case neck.  That's a tight neck!

I think that you'll like the 280's very much, it's a fine bullet for the .44 (my personal favorite of course...).