I have a Bartlein on a target rig I think is going to have to be sent back. Shoots lights out for a bout 30 rounds then accuracy goes and start to get vertical. Powder fouls horribly with several different powders. All manufacuters can make a dud every now and then.
In what way is powder fouling the barrel manufacturer's fault? I could see it being their problem with copper fouling, bore finish has a large effect on that. What is the cartridge and how fast are you shooting?
