Keyholing is normally a sign of a shot-out barrel.
Could you ask the seller to take it back on the basis that it doesn't do what it is meant to do,namely shoot properly?
Next time, I could suggest: either ask to try it at the range before buying, or ask to see a 100 meter target which the rifle has shot.
The fixes for this problem are either flat based bullets [virtually unobtainable] or cast over-sized bullets [for dedicated reloaders].
Sorry about this.
Rob