My plan is to make the 100 yard target above my line of sight to see my 300 yard aiming point and catch the groups on paper at 100. I will be impacting about 4-6 inches high at 100 with a 300 yard zero. I may even plan to impact higher at 300 to get more room on the 100 yard target. I'll try to shoot next week.

Yes, the 230 Berger is much longer than the 208 A-max. At the speeds I'm looking at (2400-2450 fps in a 308 Win), it shows a 1.05 stability factor. That's not enough. (Plus, this bullet is twice as expensive as the 208!!) With the 208, I'm looking at a stability factor of 1.27, which should be ok. 1.4 or greater is for sure stability, and the 1.3 area will also work, but is getting away from the 1.4 area. I don't like to go less than 1.3. My 208 out of my 300WM is a 1.35 at 2950 fps, which I've taken out to 1780 yards, and works well. The 1.27 should be ok. I think it's just right for this test.

That's the way I was thinking it could be done. It will be interesting to see the results.

Just out of curiosity why the 208 vs 178 if it seems you are having challenges stabilizing it?

I think the lack of stability, or right on the edge of stability is what exhibits this issue the best. Plus, I've already seen this issue with the 208 in a 308 before.

The way I read everything is that the bullet is the best stabilized leaving the barrel. So it's either stable or not.

A 178 out of a .308 Win will print small at 100 as well as 300.

The wobble on a top is caused by off axis torque (OAT), which is the same thing that causes a frisbee (one of my other hobbies is disc sports) to wobble when released. OAT is defined as unbalanced force applied in a direction other than the axis of travel.

To explain further -- imagine if you were dropping a top rather than spinning it on the table -- the axis of travel is vertical and any force on that axis will not cause wobble. Unbalanced force along the X or Y axes will result in wobble.

How could this happen in a firearm? My first thought is barrel harmonics causing unbalanced force on the bullet (as it is riding the wave it's being pushed up/down/side to side) in a direction perpendicular to the direction of flight. poorly cut/crowned barrels will do the same by allowing gas to exit on one side of the bullet before the other.

(edit to add details past here)

Further -- just as a top and a disc will quickly lose that wobble if they have enough spin, the gyroscopic inertia of a bullet will self correct and remove the wobble during its flight. That straightening/correcting force is not "free" however, and necessarily slows down the rotation of the spinning object as force is exerted.

I went to the range yesterday to get started on this project. My first load with the 208 A-max out of my 308 was a little hot. So I need to pull some bullets and reload them. I'll try it again in the next few days.