You want top accuracy or speed? You don't all ways get both at the same time.If it really is a slow barrel I'd drop down to a 120 nbt try slot of different loads with RL-19 & 22 then burn the barrel off it shooting it a lot. 1st maybe try another chronograph and bump your powder charge after assuring the chrono is ok. Rebarreling is the most expensive option but it isn't the only option. The slow velocity your getting will still kill every deer you can intelligently take a shot at. MB
