GS Custom makes a big deal out of bullet stability factor. And I believe they are a leader in bullet design for long range and other applications. For instance they are building some of the longest bullets made, 5-7 caliber, like the 414 grain 375 caliber. GS recommends: SF > 1.6 for dangerous game bullets at close range, SF > 1.4 for normal hunting up to 500 yds, and SF between 1.1 and 1.5 for long range. The later is so that the bullet will nose over at long range. So if we spin our bullets as needed for long range accuracy, they may not be stable enough if they hit a heavy animal. My thinking is that this probably isn't as important for a bullet that expands fairly easily like the 300 SMK but could come into play on a bullet like the 265 TTSX, both 338 caliber. What do you think? Why don't the other bullet makers give this info? Do I need to be concerned if I load a 150 TTSX in my 7mm 10 twist? I would just be guessing on the SF for the later.