Using Hornady 250 grain bullets in my 338WM, sako mod 75, I was getting 1" groups at 50 yards using IMR 4350. Just could not get it to shoot tighter! Changed to IMR 4831 using the same bullet, immediately the groups changed to one ragged hole groups.
So some bullets like some powders I guess!!!

More often I've notice more difference in group size based on bullet maker/type/weight when using generally recommended powders for whatever you are loading.

The notable exceptions to this in my rifles have been with switching to IMR 4064 in both 6.5X55 and 100 grn Nosler BT (1:9 twist) and 150 grn Nosler BT in .308 Win. From good to great!

Your mileage will of course vary; bottom line is its great to find combos that fit up a bug backside however it happens for you

Had a similar experience with my 284 Winchester.
I was using 4350 and got about 3/4" groups at 100 yards. Switched to RL-15, and cut the size of the groups in half.