mainehunt

I'm shooting Carbon Force 300 arrows with 100 grain heads. My bow is tuned well, and shooting great. With these 100 grain points, my FOC is something right around 7%.

Just for the heck of it I tried some 75 grain heads to see how they would shoot. They actually grouped better! I mean a lot better. I was getting inch and a half groups with the 100's, (3 arrows) with the 75 grain heads, The 3 arrows were all touching on several groups.

How do I explain this?

AllenRead

It's probably due to spine.

Your bow is tuned for an arrow with a stiffer dynamic spine. This may be intentional or accidental.

ewolf

Ditto what Allen said. Put the 100 grain points back on the arrows and turn the poundage down on the bow. It should also improve accuracy. What does your bareshaft tell you?

mainehunt

I only fired a bare shaft a few times, and it wasn't one of my own arrows and was also a different spine.

I guess I'm going to try some 75 grain broadheads and see how they fly.

According to the chart for Carbon Force arrows, the spine is OK for my arrow length and poundage, BUT it is at the top-end of the scale.

Another question......my arrows are overhanging my rest by about an inch and a half. Should I trim these shorter to stiffen the spine?

Straightarrow

I find most carbon arrows under spined according to the charts. Those are really wild guesses anyway. It depends on other factors like the cam type, draw length and brace height. Shoot the bare shaft arrow while adjusting poundage and you should be able to figure out the best draw weight to shoot your current set-up at. Err on the stiff side if possible.

Snood Slapper

I totally agree. Especially after spending so much money to find that out.