Not being funny- but I'm not so sure 10fps on a 600fps+ gun is indicating there was any gain specific to the hole- maybe you cleaned some crap off the hammer, or re-positioned the hammer spring or ...

Not saying this isn't valid- but on gains below 2% it strikes me that just about anything could do this, perhaps something completely unintentional. Now if you could do 10 simple things that add 10fps each...