Heed the man's words.
You show good instincts by reconsidering, and doing your research. While you're at it, back off
five grains, and put together 25 rounds in groups of 5 that increase in 0.5g increments. That way you can get a better feel for what your rifle likes.
I've a friend who found that his .257 Rbts shoots just DANDY at 20% under max. He loaded up about 100 rds of it, and never considered another load. Smart guy. Preserves the bore, gave good groups, and less smack (it was a featherweight rifle) to his wife and daughter, who hunted with it. Sure, he could've tried (quite unsuccessfully) to load his .257 Rbts up to act like a .25-'06, but WHY? He had a nice load that was more efficient with his powder. Interesting note-- when my wife went to hunt deer for the first time, it was with one of my buddy's reduced-load .257s that she used. (one shot at 95 yds seemed to do the job just fine, BTW).
Even with robust magnum rifles like my Sendero .300 Win Mag, I start off low and work up. What if I were to miss a superb load by going straight to "Max"? With modern centerfire rifles, getting that extra 100 fps isn't nearly as important as getting that extra .5 MOA, IMHO.
Good luck!
--L.P.