Me thinks if you had a dollar for every mule deer killed with a .243 you'd be a happy guy! BT have been improved and they are being used on quite a few hunting shows to demonstrate their lethality. For muleys I think an accubond, partition or any other premium bullet would be a little better but it's just insurance, core lokt's have killed thousands of them. My wife has shot a lot of muleys with a .243 out to 350 yards and we haven't had any issues with the caliber or the fact it works. But throw it out there in a hunting camp and sit back and watch the debate. It's a cartridge that will do the job with proper shot placement but on marginal shots there are cartridges better designed for the job.