I think you'll really like the RL15.
It's my "go too" powder for the .30/30.
I used to prefer the BLC2/Win748 until I tried the RL15.
I've found that the max loads are easily tolerated by my Marlin.
I get 2,400fps from the 150gr Rem Corlokts with 36.0gr, and near 1.5moa groups. Penetration is not quite up to that of the 170gr however. I also get 2,300fps from 34.0gr under the 170gr Corlokts and occasional under 1moa (3-shot groups @ 100yds).
I've also found that 37.0gr is wonderful with the 130gr Speer FN, and 36.0g under the 125gr Sierra JHP (my #2 favorite jacketed bullet in the .30/30.)
The performance of the 170gr Corlokt (many other bullets in 150-170gr in .30/30 have dissapointed me!) has made me a believer and is the only jacketed bullet I'll buy in the future.
I also find that 32.0gr of Rl15 is superlative under the Lee .311-150FNGC for ~2,200fps. (I size these to .311" for my micro-groove barrel).
If I couldn't get the RL15, I'd use the 748. I pulled some Winchester 150gr HP factory loads. It had what I believe to be 35.7gr of Win748. They chrono'd 2,275fps which is very close to what I've seen with my reloads. The books recommend a max of 37.0gr. for 150gr bullets, although I've gone as high as 37.5gr for ~2,300fps from a 20" bbl. (the manuals give velocities from 24"bbls).
My .308 really likes the RL15 too, as well as my .338/06, and 7mm08.