I don't know what the 130gr TSX will do from the 300 mag because i don't own or load for one but i do know that it's pure deer poison from my 30.06. I use to shoot the Hornady 130gr sp in my 30.06 with good results but was looking for a better constructed bullet in that weight range and the Barnes tsx seemed to fit the bill.It took someload developement to find the right combination but once i did it proved to be very accurate in my Rem 700. I shot 2 deer with it last year one at 288yds and the other at85yds. Both fell right there and there was no bullet recovery. The bulletmade a nice wound channelso i assume it mushroomed very well. I've tested these bullets in dirt backstops, stacks of wet phone books, and several other itemsand they do indeed retain almost all of their weight, or at least they do in those items if that means anything. When i was looking for load data i emailed barnes and they were very helpful and sent me some data so you may want to do the same.Mike
