Originally Posted by Centaur 1

The 340 is the spine, you get that off of a chart that the manufacturers put out. The minimum amount of weight you should shoot is 5 grains per pound of draw weight, this is how they determine IBO speed. Most people agree that you should shoot an arrow that weighs 6 grains per pound. The absolute minimum weight arrow out of a 76# bow is 5 x 76= 380 grains. At this weight the bow would become pretty noisy so I believe also that 6 grains is a better starting point, 6 x 76 = 456 grain arrow. The ones that your using now weigh 10.4 x 30 = 312 grains. Then add 100 grains for the tip and about another 35 grains for inserts, nocks and fletchings for a total of about 447 grains. I'd stay right where you are and not go any lighter.