So this may sound stupid, I've never had a key hole problem. How do I know which barrels are prone to issues. Mine has a #8 stamped on it near the receiver.
The ones with Ser #s begining with Y see to be fine. But ultimitly if yours is not keyholing then that is proof in itself.
Mine starts with a Y serial number and it keyholes com bloc ammo. Wolf of various weights does not keyhole. I have heard from other people with Y serial numbers that also keyhole. I think it is kind of hit and miss with the newer ones. My friend got one and it does not keyhole.