It's easy to find out how thick the jackets are on various Ballistic Tips, using at least a couple of methods. One is to put the bullet sideways in a vise and then file it down until the core shows. The other is to dump one in a pot of melted lead. In a few seconds, you can fish the empty jacket out and weigh it.
I haven't done either with the 6.5 120, but did recover one from an animal, a pronghorn doe. Muzzle velocity was 3100 fps, and the doe was quartering toward me at 250 yards. The bullet was found under the hide at the front edge of the hindquarter on the opposite side, retaining 59.4% of its weight.
