For a 30.06, is the 1 in 10 twist barrel the standard?

The reason I ask is I'm having one heckuva time getting my (new to me) '06 to tighten up the grouping. I just started using IMR 4350 & that helped quite a bit.
For a 150gr Nosler BT I have tried IMR 3031, 4064 & 4895.
For a 165 NBT - same powders. The 165gr shoots about 1.5" at 100yds. The 150gr NBT went from looking like a buckshot pattern to around 2" at 100 yds.

Other info - Brass is good, WLR primers, tried different seating depths, bolt face is OK, lugs are lapped, don't see anything bent, re-torqued the action a few times (synth stock), all the usual stuff.

I'm considering trying Hornady SST's. Maybe the rifle just doesn't like Nosler?

One other tid bit - I used a box of Unknown 150's and they shot within 1" at 100yds but, they were blemished & on sale at Midway & I have no idea what they were. All I remember was the tan colored plastic tip. I think I recall somone telling me they were Rem Accu Tips (I think) & that only happened one time out of a box of 100.

This has been a 3 month long endevour & I'm at the end of the line. I don't think it's me since I use the Lead-Sled when testing bullets / powder combos. The only constant I've had to work with is it won't tighten up less than 1". My other '06 puts this one to shame.

I wondered why that guy was in such a hurry to sell it to me...