kique,
The LRX has a somewhat higher ballistic coefficient than the equivalent TTSX. The 168 TTSX has a listed BC of .470 and the 180 .484, while the 175 LRX is llisted at .508. The LRX is also designed to expand more reliably at longer ranges.
The E-Tip was designed with a wider, deeper cavity under the tip from the get-go, the reason it tends to expand a little wider than the TTSX. When Nosler was developing them, I handloaded some protoype 180 .30's in the .300 Winchester and took them to Africa, field-testing the bullets on a variety of animals, among them several springbok (a little smaller than pronghorns) at around 400 yards. They expanded fine at that range on those small animals, but I've never used them at 500-600. Nosler lists the BC of the 168 at .503 and 180 at .523, and says they'll expand down to 1800 fps.
