Calculating FPS

[CT.HNTR]

Is there a formula or rule of thumb to use when trying to calculate FPS for different arrow weights. So for instance if my Bulldog 440 shoots a 350 grain arrow at 440 feet per second how can I estimate how fast it should shoot a 390 grain arrow?

[janesy]

Is there a formula or rule of thumb to use when trying to calculate FPS for different arrow weights. So for instance if my Bulldog 440 shoots a 350 grain arrow at 440 feet per second how can I estimate how fast it should shoot a 390 grain arrow?

I have found 1 fps reduction for ever 2.5-3 grains added to the arrow. Typically you would drop 20fps by going up 50grains.

But it's not linear, so I would hazard a guess that you will drop 17-18 fps by going up 40grains off of 440 fps.

Regardless, I'm my play time with a assassin420, it loves 435-450grains and it rocks the target around at 40 yards.
Forget about speed and make that energy work for you, they work better with weight

[nchunterkw]

Yep, what Chris said above. The EXO series seem to drop 1fps for every 5 grains, the Matrix/Micros seem to drop 1fps for 2 - 3 grains. MANY MANY MANY on here will tell you from experience that a 400 - 450 grain arrow with a haevy front end will improve accuracy and perform very very well on deer, passing through in most situations.