You brainiacs are right.A graph of kinetic energy on the y axis and arrow weight on the X axis looks like a parabola. There is an ideal arrow weight that maximizes the KE function. For my bow, thats around 12 grains per inch. If I go heavier than 12 gpi, kinetic energy starts to go down.

In addition, the momentum function also has a similar curve. However, it reaches its maximum value at a much heavier arrow weight than the KE curve does. For my bow, I thinkmaximum momentumwas around 16 grains per inch if I remember correctly. Beyond 16 gpi, the arrow velocity drops off very quickly so momentum actually starts to decrease with increasing arrow weight.

If you have On Target software, play around with different arrow weights going from 300 to 900 grains. Start a spreadsheet to calculate both KE and momentum for each arrow weight. Plot each function and notice that the optimum arrow weight for maximum KE is much lower than the optimal arrow weight for maximum momentum.