How much does weight effect speed?

Just wondering, how much does the weight you crank your bow to effect the speed of your arrow? Right now my bow is set at around 65lbs but can be cranked up to 70lbs, how much speed does the 5lb difference give you?
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BIG R
There are many varibles depending on ,what type of bow ,what arrows and weight.
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swbuckmaster
this formula works for pretty much every bow i have worked on

you can typically see 10 fps for 1" draw
3 fps per lb of draw weight
and 1 fps per 3 grains of arrow weight

So you should see about 15 fps for your set up!
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