Bullet keyhole / tumbling problem...BHW barrel???

[dvrod18]

I am by no means an expert, but the only time I have ever heard of someone having this problem was with a .22lr with excessive lead build up in the barrel. Esentially the bullet was running down a smooth bore due to the lead build up which did not allow the rifling to spin the bullet. Shorly out of the muzzle the bullets would start to tumble which caused the key hole results on target. Sounds like to me the problem in indeed the barrel.