As stated above, you're going to have to compress to fit the 70gr in but, regardless of the load weight, you need to compress. You'll find that your charge burns significantly cleaner and more consistantly. Since you're just starting out on Black Powder cartridges, I would suggest that you make a compression tool using a dowel rod and a piece of wood drilled to accept the dowel as a handle. Simply compress the powder using the dowel and try to get a uniform pressure of say 15 to 20 pounds. I'm not a fan of the compression plugs simply because I found it hard to get a uniform pressure. I took the $40 hit and bought a Montana Precision
that I can adjust.
A drop tube isn't a must, especially if you are not loading full loads. For instance a 45 Colt Gallery load that I use is 20gr 3f Goex or Swiss, a .060 veggie wad, compress with dowel, fill the brass to the top with cornmeal, then compress with compression die to correct depth, thumb seath a 150gr El Paso Pete Ultra Gamer
(EPP) and lightly crimp. If you wanted to you could also substitute a round ball instead of the EPP, but the EPP's are lubed and cheaper.
You will find quickly that "Historical" loads aren't necessarily going to give you the best results. I've managed to cram 40gr of 3f Swiss into a 45 Colt case and seat a 235gr RNFP and I can assure you, they will slap the snot out of your hand when they go off, not exactly comfortable to shoot.
Hopefully you will have fun with Black Powder Cartridge loading. I personally will put Black Powder in any cartridge I can get my hands on with the exception of auto's for what should be obvious reasons.
Black Powder Cartridge Loading Can...
Be Labor Intensive
Cause Filthy Dirty Brass that needs to be washed before it can be tumbled.
Take twice as long as Smokeless reloading.
Be difficult to find supplies for, (BP lubed bullets, powder)
Use more components than Smokeless loading
And puts one the biggest grins on my face as well as others when I fire them, that make it all worth it!!