Online calculators

[Merky1761]

How precise are those online speed calculators? I don't have a chrono yet and was curious so I put in my arrow numbers and I just don't believe it's right.

18" GT Devastator ( cut down)
110 gr brass insert
4 inch vanes
100 gr F.P
TOTAL WEIGHT- 385 grains
With these numbers archerycalculator.com is giving me 382 FPS..

Matrix 330..

[nchunterkw]

Your bow is rated at 330fps with a 350gr arrow.
A good way to estimate is to figure you lose 1 fps for every 5 grains above 350.
382gr-350gr = 32gr
32gr/5s = 6.4fps

330-6.4 = 323.6fps

Hope that helps

[xcaliber]

Matrix series denominator is close to 3. I would say close to 318 FPS, That model does perform a bit higher than rated by 2 - 5 FPS, so 321 is my final answer.

[Merky1761]

Thank you!

[Cossack]

You also have to take the brace weight of your bow into consideration. A bit longer string increases speed, albeit not to that extent.