I put a dab of shoe goo in front of the hole... (idea derived from 0-ring).
On the 99. I have a 99f. The barrel is real thin. I have not shot it a lot at the range. It has less than 30 shots through it... (50 years) Mostly into deer, for which it is used. My m77 light weight Ruger walks like crazy after 2 shots, but is a terrific deer gun. My point is that I believe that thin barrels heat up quickly, and there goes range accuracy... until cool down.
I'm not a range guy, but the time I do spend there getting my deer rifles
sharp, has been greatly enhanced by those of you who shoot a lot and
share on this board!!! Thanks, Scotty