Looking at my first custom build.

I don't know how much more accurate your going to get over what you have. What are you expecting out of a custom? The hand of god to deliver the 30 cal bullets into a 22 caliber hole with no elevation or wind needed?
 
If those two rifles aren't getting it for you, you might consider bowling or golf as an alternate hobby.

How far out do you plan to shoot?
At how small a target?
Moving or stationary?
Shooting back or just sitting there?
 
What site has the "hand of God" accessory? I'll take 2, please. It's pouring rain, here, and I guess I'm suffering a touch of cabin fever. I was tossing around the idea, for a while, only because I have quite a few 308s, and I rarely shoot the 300. Figured it was a dumb question, so....
I don't know how much more accurate your going to get over what you have. What are you expecting out of a custom? The hand of god to deliver the 30 cal bullets into a 22 caliber hole with no elevation or wind needed?