[lugerholsterrepair]

keyholing is caused when the bullet fails to achieve dynamic flight and that is usually a number of things collectively. Is there any bulge in the barrel? Run your finger along the shaft to detect even a bump you can't see..
Like Mark says..check the muzzle diameter with a 9mm bullet. Does every bullet keyhole or only some? 7 yards and something is seriously out of whack..have you shot any at say 100-200 feet to see if bullets are striking the dirt feet or yards off?
Have you looked at the witness marks to see if they are aligned? Is the barrel tightly screwed in?
The lands and grooves are there to provide twist to stabalize flight..there might just not be enough.