I have been shooting a 243 for the past two years my load has been 45gr of n160 and an 87 grain hornady v max. I have fired about 2000 rounds and am now noticing my groups starting to open up alot i have never fired rapidly and have always cleaned the barrel after use.is 2000 rounds about all you can expext from a 243 factory barrel.Am looking into the 6 mm br and am wondering what sort of barrel life can be expexted from it.thanks alot.