100 grain bullets work fine on deer in the 25-06...

If you use 115-120 grain bullets in the 25-06, ballistics basically match 270/130 grain ballistics...

The 100 grainers in the 25-06 will shoot slightly flatter and kick slightly less than the 270/130, but as I said before, you are splitting hairs here..

Before someone jumps on me, I am aware that there are 100 grain bullets available for .270 also, BUT most of them are are designed for varmint hunting, whereas 100 grain .257 bullets are designed for deer sized game...