One gun 2 hpa tanks

[Bababing]

Hi All,

I have an unleashed mtw which came with a tank they are pretty small so I thought I would get another one a Lippmann one its just a little bit bigger but fits on the gun all and well, the thing I have found tho is the gun is shooting a bit more it shoots 290fps with the tank it comes with and the new Lippmann is shooting over 310fps / 1.4j, is this normal or do I have to reset the reg each time I swap the tanks over?

thanks for your time.