In testing, I think you want something around .130 or smaller, in good/consistent wind conditions. So, you are getting close. Keep playing around, you can't rush the process of testing. Once you get around .130 or so, and this is for a 3-shot group (hopefully more of a round group and less of a Mickey-Mouse looking group), you're ready to compete.
I assume you are using a Berger bullet, since you mentioned 115 grains. That's a fine bullet - if you can get it to .130, you can be very competitive with it and win with it. If you can't get around .130 with that bullet, I'd try a different (custom) bullet before I'd try a different powder or primer. Too many folks shoot extremely well with LT30, it's a winning powder. If after testing a custom bullet and LT30 in your rifle, if it still won't hit .130 or so, then I'd break into VV130. And repeat all that testing...
This may or may not apply to you, but looking back at when I first started this game, I think I focused too much on thinking that this "magic" powder or primer or front rest or brand of case or rear rest was the key to winning. Now, I realize that what I really needed was practice time, and more experience/time in reading the flags. Actually, I still need more practice time and more time reading the flags.

Remember, the best shooters win most of the time. Your equipment and load have to be competitive, but you can't buy wins and you can't short-cut gaining experience. One of the best shooters (he wins a LOT) I regularly compete against, who has been shooting for many years, uses a leather rear bag that looks like my grandfather could have used it. Talk about old! But, this shooter knows his gear, knows his technique, and is a master at reading range conditions. That's the key right there.
Good luck and have fun!