New here and always worked with reloading books for working up reloads. I recently came across several boxes of heavier than normal 125, 130, and 135 grain .257 spitzer bullets I would like to try in a .25-06. Would using the starting charge weight of the 120 grain bullets listed in every book out there and working up be ok? Or should I start lower?

I would use starting loads for the 125s, and drop a grain for the 130 and 135s, assuming your COL doesn't change from the factory manual. If you push the bullet up against the lands, all bets are off, and I would drop back about 10% just to be safe.

Good luck; I hope the twist in your rifle will handle the heavier projectiles...

Twist is 1:10 and if they don't work well I am out very little except some range time.