Although there are a small group of bowhunters who use heavy (over 125 grains) heads, I would suspect that 90% or more are shooting 100 grain tips. The reason to shoot the heavy head would be to increase the FOC (front of center) balance of the arrow and to provide increased penetration.

What the vast majority of folks I know have discovered is that, for regular critters like deer, elk, and black bear; the 100 grain heads provide very adequate penetration and very good accuracy. Good balance between speed and penetration as well.

Arrows of the proper spine are going to shoot straighter than arrows that are either too soft or too stiff. And they will allow you to properlytune your bow, which is almost an excercise in futility with an improperly spined arrow.

Last spring, I got some Easton ST Axis shafts. With my 61 lb. Hoyt and 100 gr. heads, I got the 400 series shafts. They come 31" long. After pouring over the charts, I figured that cutting them to 29" would put the stiffness very close to ideal. I could have gone as short as 27.5" because the arrow rest is set back on the riser, but thatwould be just a tad on the stiff side. So cut to 29", I shot a group with some of the first arrows I fletched and compared the point of impact with some bare shafts not yet fletched. The hit exactly the same spot at 20 yards. This is, in my experience, the acid test for correct arrow spine. If the shafts were too soft, the bare shaft arrow would hit to the right of the fletched shafts. And too stiff of an arrow would cause the bare shafts to hit to the left of the fletched arrows.

With the shafts spined to perfection, getting field points and broadheads to shoot to the same point was relatively easy.