I will only now buy 5 cavity molds or larger# cavity molds from either NOE, Arsenal or Mihec, even the newest LEE 6 cavity molds are supper consistent IMHO. Their proven track record of uniform quality molds speaks for its self.
There is much knowledge available on PP w/ Black or smokeless powder in Cf rifles a simple search of this internet thing will keep you reading for days.
Here is a link to a good source of knowledge :
http://castboolits.gunloads.com/forumdisplay.php?62-Smokeless-Paper-Patching
I just went down to my shop and counted molds, LOL. I only have 19 molds that are, 5-6 or 8 cavity that I use regularly. I shoot my own cast in everything from, 22 K-hornet to 50BMG I have hunted exclusively with my own cast since 98. It has actually much longer than that with my 12 ga slugs, RBs and all forms of ML, Maxi, Minis, REALs. Many of my family and friends use my boolitz to harvest critters. If you shoot a lot, cast boolitz makes sense and is my way to have a tremendous amount of fun.
Long before Magnumeitus became a marketing tool of manufactures, animals were cleanly harvested with lead boolitz. I believe it wasn't until 1908 that the Gas Check was developed, the first bullet designed for it was the, Ideal 308284 a modified version of the 308282. The gas check shank was added to it. It was developed for the army to allow for a more cost effective 30-06 round for military to practice with out to 600 yards.
With todays machining capability on CNC machines, there is IMHO no reason to buy single or double cavity molds. I suppose if you only shoot 10 to 20 rounds a year.
Ken