Rather than explain my entire situation, I'll provide my question with a more general example. If it takes 5.0 oz of sucrose to achieve 3.0 vols, why is it not the case that 2.5oz = 1.5 vols Is it a logarithmic scale or something similar?
I believe it is because there is already some dissolved CO_2 in the beer after fermentation even before it is carbonated. That is why some priming calculators want you to input the temperature of your beer, because the amount of dissolved CO_2 depends upon temperature.
Ah. Therefore you cannot "double the recipe" because you'd be counting the dissolved c02 twice. That makes sense and makes me feel better. When I primed my fruit beer I added an extra 0.7oz of sucrose to my 4.5oz corn sugar to up the carbonation. I initially just used a reading for 5.2oz of sucrose as a conservative estimate. I later went back and did them separately and got 2.8vols (for 4.5oz) + 1.2vols (0.7oz) and got myself into a needless "bottle bomb" panic. Thanks