You are missing some pretty fundamental basics of reloading.
The OAL on the drawing from page 219, is the SAAMI max length. The 2.775" listed on the next page is the length actually tested at. If you aren't going to test the throat length of your specific rifle, you use the number which is specific to the bullet.
The length and shapes of the SMK and the A-Max, ARE NOT the same. So your distance to the lands will also not be the same. Because the construction, and the jacket material are different, the pressures will also be different.
Just because something weighs the same doesn't mean it is the same thing. Spend some time reading the loading information in the Lyman manual BEFORE you go to the load data, this is covered in that info...

You will also find that unless you have a specific reason to run max speed, the more accurate loads are generally near the lower end of the velocity range.