Okay, since I'm leaning towards a 1:8 twist barrel, I'm thinking the Lee .309 200gr RN is good one to run for subs in place of the possibly-slightly-too-long .309 230gr 5R boattail.
Only problem is it's a gas check mold. I've never tried shooting a GC bullet without actually installing the GC, but I don't see any reason for a GC with these subs, especially powder coated. Seems like unless I want to go for another brand of mold (expensive), I have three options:
1) Go with the 230gr and hope it stabilizes in a 1:8 10.5" barrel
2) Go with the 200gr and shoot it without a gas check
3) Go with the 200gr and shoot it with gas checks
Any recommendations? I've heard of shooting GC bullets without actually putting a GC on first, but never tried it.
Edit:
Also looking into powder choice now. From what I can tell, it's down to about four or five good powders for running heavy subs, each with at least one major drawback:
1. IMR 4227. Leaning towards this one, although it's kind of expensive compared to other options. Ah well. Also has the advantage of apparently working quite well for supers, should I ever decide to play with those.
2. Accurate 1680. People seem to love it, but I also hear it's ridiculously dirty in a pistol length gas system (this would line up with Ian's experience)
3. Accurate 5744. Apparently meters like pencil leads.
4. Reloader #7. Burn rate is in the same neighborhood as the others, but I can only seem to find people talking about it in ARs with longer barrels.
5. CFE BLK. I can't get it locally.