Piston weight difference

I had 7 pistons at x, and 1 piston and x-2g. I hit the inside of the pin with a Mig wire and built up the 2g there. The pins were floaters so EZ to slide out and weigh. I scrubbed the inside with a brush to make sure no slag was left in there. I took weight out of the pins in another case where I had 3 pistons that were >+5g out and there was not 5g in he piston to take out. Strange lot of pistons there.