Could be but I'm running the same load as other guys and they are only getting 3200-3250 when I was getting 3400...
And I had two 300ultramags,but one produced 100fps more with the same load.However both rifles produced very similar velocity before showing any signs of excess pressure.One rifle may have had a slightly smaller chamber,so it simply made more pressure,and therefore more velocity, with the same load.Some individual barrels do produce more velocity than others at similar pressures,sometimes even supposedly identical barrels by the same manufacturer.