Hw do i FIND MY FPS
 

I have a Browning Rage with a 28in draw and and 75#draw how do i know how fast im shooting with out a crono?

RE: Hw do i FIND MY FPS
 

Ok, its not easy but this is what ya have to do. Set up a target the size of a VW bug, then get in your truck and drive 100 yards down range. 100 yards =300ft and that is what you will be shooting around, now shoot and count 1 mississsippi, 2 mississsippi. If it takes 1 second to get there then you are shooting 300 ft per second.

I am not serious, I have no idea how to do it with out a crono. [:-]

RE: Hw do i FIND MY FPS
 

[8D] i can help you with this i know it. you need to weight you're arrows with you're feild tip or broadhead on it. then you need get a cronograh and see how fast the bow shoots the arrow. then you call a good bow shop and ask for the formula for kinetic energy. just be sure to writ this formula dow and keep it in a safe place. i do this with my arrows all the time. but you need to know the speed/weight of the arrow. good luck

RE: Hw do i FIND MY FPS
 

Simple with the following generalizations. Start with the IBO speed for your bow. I believe it to be around 295 fps.

Subtract 10 fps for every inch of draw length you are below the 30 inch "test standard". In your case that means a loss of speed of about 20 fps.

Next subtract approximately 1 fps for every 3-4 grains of arrow weight you are above the IBO "test standard" arrow weight of 350 grains. (a 460 grain arrow would cost you about 27-34 fps)

Next add or subtract approximately 1.75 fps for every pound of draw weigth you are eitherover or under, respectively, the IBO "test standard" weight of 70 pounds. In your case that means you gain approximately 8-9 fps.

Lastly, subtract approximately 4-5 fps for every string accessory you have installed on the bow...peep sight, string silencers, string loop, etc...

Then take all of those numbers and subtract/add them to your IBO speed rating to determine a fair estimate as to your speed.

RE: Hw do i FIND MY FPS
 

:Dok here we go again! this is how youfigure out the kinetic energy of you're arrow. first you need to know the speed of the arrow. then you have to know the weight. here is the formula for figureing out the kinetic energy of you're bow&arrow.MULTIPLY SPEED X SPEED XWEIGHT DIVIDED BY 450240. HERE IS AN EXAMPLE 260FPS X 260FPS X415ARROW WEIGHT EQUALS 62.30 FT LBS OF KINETIC ENERGY OF THAT ARROW. HOPE THIS HELPS ALSO THIS WILL HELP YOU IN PICKING OUT THE BROADHEAD TO SHOOT ALSO. IT IS RECOMMENDED THAT 65FT LBS OF KINETIC ENERGY BE USED ON MECHANICAL BROAD HEADS OR HIGHER THAN 65FT LBS.GOOD LUCK. JIM

RE: Hw do i FIND MY FPS
 

[&:]

RE: Hw do i FIND MY FPS
 

This chart works out pretty darn close. The only thing is you have to beable to shoot pretty good groups. The tighter your groups the better you can measure. Plus, you have to be dead nuts on sighted in to begin with. Anyway,,.... it does work. Use the bottom chart(the red one)where I've realigned them for easier reading. Shoot at a target from 20 yards away with your 20 yard pin. Have your spot near the top of the target because you have to allow room for the next group to fall low. Make sure you're on. Back up to 30 yards and shoot the same spot with your 20 yard pin AGAINMeasure the distance between the center of the two groups. Read from the chart to see your speed. For example: If you get a drop of 13 inches your speed is 258. The 60/30 foot chart(20 years/10 yards) chart is for really slow bows, like trad stuff.

DISTANCE= 90ft and 60ft (30yrds and 20yrds)

INCHES= 8 9 10 11 12 13 14 15 16 17 18 19
FPS=322 310 294 280 268 258 248 240 232 225 219 213

DISTANCE=60ft and 30ft (20yrds and10yrds)

INCHES= 5 6 7 8 9 10 11 12 13 14 15 16
FPS= 322 294 272 255 240 228 217 208 200 192 186 180


Drop in trajectory between 60 and 90 feet (20-30 yards)

Speed Drop


322 8
310 9
294 10
280 11
268 12
258 13
248 14
240 15
232 16
225 17

RE: Hw do i FIND MY FPS
 

If you use PABowhntr's calculations you will come up with a speed as if you were shooting through a crono.

Now I believe if you use davidmill's calculation's you will get the downrange speed which will be a lower number.

Your bow will be shooting the same speed but is quicker coming off the bow and slows as friction slows it down range.

For setting the speed on my Savage QCRanger I need to have the more exact down range speed . which is about 30 fps slower than the crono.
So if you want to brag about your speed use PA's numbers , if you want reality use David's:)

RE: Hw do i FIND MY FPS
 

:D...Nice. ;)

RE: Hw do i FIND MY FPS
 

David, at 30 yards, my bow drops around 18inches. It's a slug with my arrow weight and small draw and low poundage.