The 'last' generation of BT's could be driven too fast to be effective. I was pushing 140 grainers out of my 7mmMag pretty hot and during one particular doe season, shot several does and only recovered one. I contacted Nosler and was told that this was a noted problem and they were fixing it. I later received 200 'new generation' BT's in the mail from Nosler to try. They have proven to be very effective.