# speeding up my bow!?!



## sawtoothscream (Apr 19, 2008)

lower arrow weight
take everything off string and limbs but peep and d loop
add draw weight
add speed nocks
much sure its in perfect tune

sounds very slow for your specs on a 320 ibo bow. ran it through a archery calculater (was dead on wheni ran both my bows specs through it) and it says you should be around 280fps with that set up


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## easton shooter (Oct 14, 2010)

I shoot a 400 gr arrow and 100 gr tips. The only other set up ill shoot is 340's


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## nuts&bolts (Mar 25, 2005)

easton shooter said:


> I shoot a 400 gr arrow and 100 gr tips. The only other set up ill shoot is 340's


Try another chrono.

Martin Cheetah at 70 lbs of draw weight, and a 28.5-inch draw length...and assumed your letoff percentage = 80 percent.

should be getting about 302 fps.

You didn't mention your arrow specs..

so...

I assume Easton ACC 3-60 aluminum/carbon shaft...these are 340 spine rating (stiffness)
raw carbon tube length = 28.5-inches long

assumed Blazer vanes

assumed 100 grain broadheads

The total arrow weight = 399.3 grains...practically 400 grains of total arrow weight.

The IBO speed rating for the 2009 Martin Cheetah = 315-320 fps


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## easton shooter (Oct 14, 2010)

im shooting an easton st epic carbon arrow 400 gr and at 29 in with a 28.5 in draw and it wont shoot no dang faster. 
100gr broadheads
b;azer vanes


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## nuts&bolts (Mar 25, 2005)

easton shooter said:


> im shooting an easton st epic carbon arrow 400 gr and at 29 in with a 28.5 in draw and it wont shoot no dang faster.
> 100gr broadheads
> b;azer vanes


Do you mean the Easton Epic 400 "spine" arrow?

If so,
then this arrow is not stiff enough for your bow.

You should be shooting the Easton Epic 340 arrow.

Have you measured the Axle to Axle length on your bow?
It should be 30-inches exactly.

Brace height should be 7-1/4-inches.

Try shooting any 340 spine rating arrow,
and see if you get a different chrono reading.


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## easton shooter (Oct 14, 2010)

thats what i was shootin before and they were the easton axis though with a 340 spine.. the archery shop iv been going to told me i should be shootin the 400 with a 28.5 draw at 70 pounds


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## nuts&bolts (Mar 25, 2005)

easton shooter said:


> thats what i was shootin before and they were the easton axis though with a 340 spine.. the archery shop iv been going to told me i should be shootin the 400 with a 28.5 draw at 70 pounds


Shoot whatever stiffness arrow gives YOU the best group sizes at the distances you shoot most often.


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## easton shooter (Oct 14, 2010)

im shootin up to 95 yards so im gonna need to shoot a few diff arrows


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## easton shooter (Oct 14, 2010)

a 400 spine arrow should shoot faster than a 340 right??


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## Rob D (Dec 26, 2009)

easton shooter said:


> a 400 spine arrow should shoot faster than a 340 right??


 400 spine is lighter then a 340. so yes, it should be faster. 

You should get the arrow spine correct before worrying about speed.


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## SonnyThomas (Sep 10, 2006)

I'm with nuts&bolts as for the speed. Reasonably tuned and a 380 to 400 grain arrow should be pumping more the 247 fps. I'd try a different chronograph.
Guessing and probably real close and if 315 to 320 fps is factory IBO, then approx. 277 fps. < Close to what sawtoothscream has.

Here's some approx. rules for calculating speed; Use factory given IBO speed.
2 fps / 1 # of Draw Weight ------------------------- 70 pounds is straight IBO, no adjustment
10 fps / 1" of Draw Length ------------------------- Subtract 15 feet per second
1 fps / 3 grains of arrow weight -------------------- Subtract 16.666 feet per second (IBO arrow is 350 grs)
1 fps / 3 grains of weight on the string ------------- Subtract approx. 7 to 9 feet per second (loop and peep)


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## easton shooter (Oct 14, 2010)

400 spine arrow is the right arrow i should be shootin and if its the cronograph thats wrong ill feel so much better


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## Bigbamaboy65 (Oct 12, 2010)

how are you shootin 95 yards if your arrow is only goin 247 fps?


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## bfisher (Nov 30, 2002)

Ummmm, if I'm not too old to remember I think I remember that recurve FITA bows shoot 90 meters (approx 99 yards) with arrows doing less than 200 fps. This has been going on for decades so 247 should make it easy.


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## m_baker_12 (May 13, 2010)

I think he means how is he shooting 90 yards out of it with a set of sights on the bow. He should run out of pin room before 90 yards if it is shooting that slow.


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## bfisher (Nov 30, 2002)

Thanks. I hadn't thought of it in those terms. Even so, it also would depend on what sight being used with enough travel to shoot 90 yards. That's probably stretching it pretty far for any multipin sight.


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## completepassthru (Feb 3, 2008)

I will tell you that almost every single Martin bow i have ever seen would not shoot anywhere near their ibo speeds.


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## camp-toner-ty (Dec 3, 2010)

if you have a peep sight with the rubber get rid of it and get like a g5 meta and if you use a wiscker biscut that will slow you down


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