buckstix,
Since you are going to play with a lot of different rifles, it seems like it would be worthwhile for you to buy a lathe, if you don't already have one. If a 45-70 seating die( w/o stem) wouldn't work to get 450 cases to chamber, you could make a simple ring die to do it. You need one anyway for rims. I believe a lathe( and mill) is a requirement of life. Like doing what you want with your own rifle, you are entitled to decide for yourself whether you want a lathe or not.
Mike