That's about right. Most of all my loads compress the powder a touch. Except for the garand. It's loaded weak so you hear the powder bouncing around if you shake it. Here is another formula you can try for twist rate/bullet weight calc.
“military type bullet measuring .647" in length. The bullet diameter is .224", which divided into the length of .647" gives 2.89 calibers long. Dividing 2.89 into 150 yields a figure of 51.90 or an ideal twist rate of one turn in 51.90 calibers. Multiply 51.90 by the bullet diameter (.224") equals one turn in 11.63" for this particular bullet”