Yes machine the barrel to the same dimensions "just check power" afterwards --i have found bottle pressure is a must with these guns i fill mine to around 170-but no more than190 bar i top it up after about 40-50 shots that way i no its going shoot right ---its strange that you say it was shooting ok before a scope change? i give the barrel on mine a clean when the accuracy go's off --i also fitted a tri rail to give extra scope head height that made a big difference