meck1776 said:
Have you shot them at longer distances? I test shot a real GR, not just the practice head. They were fine at 30 yds but at 40 they had dipped a few inches low and left for me.
Yes I have tested em at longer distances... out to 50 yards with the broadhead and never had a problem. Honestly I'd never shoot a deer at that distance, but I'm very thorough about testing all my equipment... so I always push the limits when I'm testing.
I'm shooting my Grim Reaper RazorTip broadheads on Black Eagle Executioner arrows. My FOC (Front Of Center) is 18.18%. A lot of archers are (actually most) are between 10-15% FOC with broadheads on their arrows and 8-11% with a field tip. I like a higher FOC cause it's better for long distance and better penetration.
The basic definition of FOC is the percent difference between the physical midpoint of the arrow and the center of gravity (balance point) of the arrow as compared to the total length.
When an arrow is shot, the fletchings immediately begin working to correct the flight of the arrow. Any little imperfection in the initial launch of the arrow, either from shooting off hand, imperfect release, improperly tuned crossbow, arrow not loaded correcly, crossbow not cocked evenly etc. will cause the arrow to flex as it leaves the crossbow and/or come out crooked. The job of the fletchings is to correct this imperfect flight by straightening the arrow as air flows over the fletchings during flight.
In order for the fletchings to correct the flight of the arrow, they must move the arrow into a straighter flight path by rotating the shaft about the center of pressure. The center of pressure is the point along the shaft where the aerodynamic forces are balanced. Just like with a weather vane, the fletchings on the back of the arrow provide more surface area on which the air can act upon the arrow.
Fletchings are best able to steer the arrow when the center of pressure is farther behind the center of gravity. This is more easily done the longer the distance from the fletchings to the center of gravity. Therefore the farther the center of gravity is from the back of the arrow, the easier it is for the fletchings to correct the arrow flight.
If the center of gravity and center of pressure are too close together, or worse if the center of gravity is behind the center of pressure, the arrow will become unstable. To witness this, take an arrow or a dart and try to throw it backwards! What happens?
For penetration purposes, the opposite phenomenon occurs. A larger FOC will prevent and arrow from flexing as much when coming into contact with the intended target. Hunters will want a higher FOC so that as the broadhead enters the the game, the distance from the front of the arrow to the center of gravity is lower, making it more difficult for the arrow to flex or deflect. Any flex or deflection of the shaft upon entry means that energy is being lost somewhere other than directly along the center of the shaft, lessening the overall penetration.
A larger FOC is necessary for shooting long distances where crosswinds tend to have a large effect on arrow flight. The same applies to shooting broadheads because the larger surface area of a broadhead is more greatly affected by launch imperfections as well as crosswinds. Broadheads effectively move the center of pressure closer to the point and tend to steer an arrow which can often have a negative affect that the fletchings must overcome.
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