Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

The Bowtech Patriot Dually's IBO speed is 326-334 fps., but that's based on 70 lbs. pull. Is there any way to estimate the speed of this bow or any other bow for that matter with a 60 lbs. pull? I'm debating getting a speed bow (Dually, Supertec, etc.) in 50-60 lbs. pull and bottoming out the limb bolts and possibly shooting the bow at 60-62 bls. vs. getting a slower smoother drawing bow in 70 lbs. pull. Which would be faster? Is there some mathmatical formula for calculating bow speed at 60 lbs. based on advertised 70 lbs. IBO speed? Thanks.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

A 60 lb. bow is approx. 4-6 fps slower than a 70 lb. model. Of course this is using a 5 grain per pound arrow.

Regards, Pat

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

And if you're talking same arrow weight, knock off about 15 fps or so...

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

That's a great question, I wish they'd supply that # along with the amo speed.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

My 03 Patriot Dually's BC shows 319 with a 300 gr arrow at 61#, 29". It went 288 with a 375 gr arrow at 57#.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

Using a 300 gr arrow... what would be the speed difference between a 60# model w/ the limbs bottomed out.. vs a 70# model w/ the limbs backed down to the same weight as the 60#er?

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

I was using 28" carbon force 100's and shot 292fps at 60# with my 04 dually.

nubo

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

Thanks for the response. Sorry I didn't clarify my question. I was talking about using the same 350 gr. arrow weight in the 60 lbs. model.

Is this statement true: You generally loose or gain about 2 fps. for every pound of weight that it decreased or increased?

I wish that archery manufacturers would supply arrow speeds based on the same 350 gr. arrow at 60 lbs. I know that this would be above the 5gr./lbs. limit that is put on IBO, but how many people really shoot there bow at 5gr./lbs.. Any arrow that I've ever looked up on an arrow chart would be way over 5gr./lbs. if it's spined correctly for the poundage. Show me a 350 gr. arrow that will be the correct spine for a 70 lbs. bow at 30 inch length of pull.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

My opinion remains that IBO speed is overdone and overrated. Most manufacturers do not adhere to strict standards when testing a bow to list their IBO speed. Although the advertised fastest bows most times are the fastest bows.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

Wolf, I agree. How about a chart with draw weight on one side and arrow weight on another the intersecting line would be the speed as shipped.

Only problem is deciding on a "average" draw length. I vote 29.5":D

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

wolf,

I just saw a 2004 Pat DC down at the local shop. It was a 29 inch draw-60 lb model that had a birth certificate speed of 313 fps with a 300 grain arrow. Going by the general rule of a loss of 1 fps for every 5 grains of arrow weight added that would put the speed at about 303 fps with a 350 grain arrow...give or take a fps or two.

Yes, but it varies depending on how efficient any given bow is with different arrow weights. Some bows are more efficient with heavier weight arrows..some with lighter ones. I generally use 1.75 fps instead of 2 fps as it has been a more accurate number for me and my setups in the past.

Ken,

I would guess something of at least 3-4 fps. Again, it varies depending on the model and the design of the bow.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

Cougar Mag, I agree completely IBO speed is very overdone. There isn't an arrow that exists, that I know of, that would be correctly spined for a 70 lbs. pull, 30" LOP, that would weigh 5gr./lbs.. I think it would be difficult to shoot a 5gr./lbs. arrow through a 70 lbs. bow at 30" LOP because it would be very underspined and wouldn't tune properly.

DaveC, (same DaveC as on Texasbowhunter.com), if so howdy fellow TBH'r. I agree with you as well that's a good idea for a speed chart. So that everyone regardless of lbs. of pull could know the speed of there particular bow. It would be much more informative for everyone than only listing one particular unrealistic setup.

It's really sad that all bow companies feel the necessity to stretch the truth (lie) to the public in order to sell there product and that the sport as a whole uses a standard of measure (IBO) to compare themselves against each other that's very unrealistic. Does an arrow exist that would be spined right at 70 lbs., 30" LOP, and 5gr./lbs.? Also why don't companies show AMO speeds anymore? Is it because we the public might see through the smoke and mirrors of marketing. Sorry if I'm venting again... I'd just like to see all archery companies use the truth in there advertising and the industry use a standard of measure to compare themselves that would be realistic, unlike IBO.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

There are several carbon arrows out there that spine correctly for 70# w/ a 30" draw that would weight 350gr...

figure a:
shaft 8gpi x 30" = 240gr
3" feathers = 9gr
nock = 13gr
75gr glue in point = 75gr
glue = 5gr (prolly less)

Total= 342gr

Arrows that weight about 8gr per inch that I found in Lancasters:
Carbon Express
CX300 8.0
CXL350 8.0
LineJammer 8.2 (.2 over)

Black Hawk
Vapor 23speed 7.5

Gold Tip
5575 8.2 (.2 over)
then there's the new ultralights.. not sure on the weight though

PSE
Carbon Force Comp Pro 300 7.8
Carbon Force Extreme 7.8
Carbon Force Dominator 8.1 (.1 over)

Carbon Tech
Cheetah 7.5
Hippo 8.3 (.3 over)

Easton
Light Speed 340 8.04
Redline 360 8.31
ACC 2-71 8.04
ACC 2-71 7.38

That's not counting any new arrows that came out this year.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

KBacon, I'm not saying that it's not possible to make a 350 gr. arrow that's 30 inches, it's just not very realistic. Most archers that I've seen shoot 4 inch vanes instead of 3 inch feathers, they also have an aluminum adapter that the field point or broadhead screws into and generally use 100 or 125 gr. broadheads/field points. I just think that using an arrow that's 400-425 gr. is more realistic.:)

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

My 30" GoldTip 5575s weight about 400 gr w/ insert, 100gr point, and 3 4" feathers.

A 4" feather weighs maybe 1gr more than a 3". And 4" vanes average between 8-10gr per.

It's not that unrealistic... it's very common. I was mainly referring to 3D type arrow where glue in points are common place. I won't be hunting w/ an arrow that light.. For hunting I'll prolly be using a 400-450gr arrow.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

wolf6151, yep= it's me!!

I wonder if there has ever been a pole done on how much the average hunting arrow weighs. A 350 grain hunting arrow seems kinda light to me.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

Dave, since you asked I'll tell ya. My hunting arrows weight 320 grains, shot at 60lbs, 27" draw. I shoot the same weight arrow for 3D--aluminum 2212's with 50gr target tips.

RE: Estimating arrow speed with 60 lbs. bow based on IBO speed.
 

IBO = 70 pounds @ 30" @ 5 grains per inch....PERIOD.
Everything else is AMO. There is no such thing as an IBO rating on a 60 pound bow.

Smoke N Mirrors, Smoke N Mirrors.

:sign0018:

does this seem like a rough esstimate of arrow speed? :eek2:

253/450=.562 fps/gr.

450gr. - 314gr. = 136gr.

136X.562=76.432

76.432 fps +253 fps = increase in speed when switching from 450gr.
arrow to 314gr. Arrow.

Chronograph data (253 fps with 450gr. arrow) from Mathews Monster TM. 56 pound draw weight

You can get an estimate from the Archery Calculator, here's a link. Hope it helps!

http://www.backcountrybowhunting.com/articles/calc/

If you want to talk about average draw length then it's closer to 28" and not 29.5".

Answering the OP's question about whether to shoot a speed bow at 60# or smooth cam at 70#? I've done a few tests of my own on this, although not scientifically. Just using a chrono, and with bows set to my draw length, but both shooting the same arrow. I can't shoot 70# so I'll just tell my experience.

Bow #1--Martin Moab--smooth cam bow set to 27" draw (measured) and 49#.

Bow #2--Martin FireCat--hard cam bow set to 27" draw (measured) and 42#.

Both bows shot a given arrow at the same speed. These are almost identical bows except for the cams. The FireCat shot the same arrow at the same speed although drawing 7# less weight. That difference made that harder cam seem a lot smoother. The arrow weighed 275gr.

I know this doesn't come near the 60# or 70# scenerio, but it should give some approximation of what to expect. Me? I'll take the lower draw weight every time.

thanks i'll give that a try

Some rules I go by
 

Every bow is slower than a 30/06. Live with it.

Measure speed by yourself by shooting practice. Get the drop-off of shots every ten yards. Get it for one bow, unless you like getting ten different bows, for your pocketbook.

Practice and get as pin-point accurate as you can. Speed won't help, if you can't hit the broadside of a barn.