Heavier Arrow?

[bownutty]

I am shooting a 70lb bow and am wondering how much speed, approximately, I would loose by going to an approximately 48 grain increase in arrow weight? My 375 grain arrow now shoots at 285fps with 70lbs of K/E and am thinking about trying a 425 grain arrow and was wondering what the K/E would end up being with the speed decrease. I know this might seem a little petty, but I am just courious.

[ijimmy]

Hard to estimate but I would say arround 265 270 range for speed , and your ke will go up slightly , maybe 1 to 2 pounds .

[Arthur P]

Figure 3-5 fps in arrow speed for every 25 grains change in arrow weight. Your KE will definitely increase with an increase in arrow weight.

[JeffB]

depends alot on the bow & cam design.

BowTech's singles, and newer Mathews HP cams will lose/gain roughly 1FPS for about every 3 grains of weight from 5 grains per pound up until about the 6 grain per pound threshold, then the ratio gets closer to a 4-5 grains per FPS.

BowTech dual cams often have a 1 FPS per 2-3 grain weight ratio up until around 6 grains per pound.

The Hybrid cam bows (C.5, CPS & copies) I've owned seemed to be somewhat the opposite...not picking up as much speed as other designs with light arrows, and not losing as much with heavier arrows. they maintain a more steady ratio throughout the range of arrow weights.

There's no cut and dried formula these days as cam efficiencies and designs have changed alot since the old 1/5 ratio was brought up.

I would guess you would lose 7 or 8 FPS assuming a typical single cam bow.

[Paul L Mohr]

My mighty might is more like 1 fps for every 2 grns of arrow weight. It also may depend on your draw length, or the way you have your cam set up? These are with arrows from 300 to a bit over 400 grns.

Paul