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Hi everyone. Have been enjoying my Onza very much, however I am disappointed with the speed I'm getting. The IBO of the bow is closer to 310fps according to Archers Advantage and OT2. I have it at exactly 70#, 27.5" draw and it is shooting a 557gr arrow at 233 fps, 480gr arrow at 255 fps and a 385gr arrow at 285fps. The bow is perfectly timed. What can be wrong with it??? Any info will be appreciated. Thanks.
I'd say nothing is wrong with it... you have a short draw on a fast bow, just like me. I also shoot a 385 grain arrow and get the same speeds out my Onza. I clocked a 356 grain arrow at 298. If 27.5 is your true draw (apex of string to riser grip) then it means you have a 29.25 AMO draw:
29.25" draw = .75" short of Ibo = -3 fps
dloop/peep = -10 fps
385 gr arrow is 35 grains higher than Ibo = -28 fps
Assuming you have string silencers, say at least 5 gr each = 8 fps
330 to 340 Ibo bow (call it 335) - 49 fps = 286 fps
Remember, the shorter your draw, the heavier your arrow, and the more things you have on your string all combined give you loss of speed. Hope that helps!
Hi. Thanks for the great reply. It helps and it all adds up. But why is my Maxxis 31 at least 10fps faster with all the arrows than my Onza? The Maxxis is rated at only 321fps IBO. Does Hoyt and Martin have different draw lengths when rating IBO/ATA speeds?Quote:
Originally Posted by wscywabbit
try add another speed nock above or below the factory ones I have found that adding one brings up the speed on my firecat 6 fps
What makes you say Hoyt and Martin use different draw lengths to find IBO ratings? ATA has set a standard of 70#, 30" draw, and a 350gr arrow. That is the standard all manufacturers use. Anything other than that is not IBO ratings. Manufacturers may list speeds at whatever specs they choose, but they won't be according to IBO specs and are therefore not a true IBO speed.Quote:
Originally Posted by deserthuntr
My Onza III gets IBO easily. 28.25 draw @ 70# 386 gr. arrow@ 302 fps. String loop, peep, and whiskers on string. I do tie my whiskers on between the speed nocks and the cams though. According to my chrono, that negates the weight, and sometimes speeds the bow up a few fps.
I don't have any experience with the onza but that sounds really fast.
My onza at 62 pounds and a 29 inch draw throws my 378 grain fatboys at about 286-289
IBO and ATA are not the same anymore. IBO can be up to 82# as long as the arrow stays 5 grains per pound, and if I'm not mistaken the draw can go up to 31". If the Onza meets IBO, then why is my Maxxis so much faster when it is rated only 321fps ATA? Is Martin IBO ratings or ATA? (ATA is still 70#, 30" draw with a 350gr arrow)Quote:
Originally Posted by bfisher
An explanation of IBO and AMO from archeryexchange.com, with my highlighting:Quote:
Originally Posted by deserthuntr
"A.M.O.(Archery Manufacturing Organization) and I.B.O. (International Bowhunters Association) both have a method for testing arrow speed from bows and although they are different both can be used to compare equipment for relative speed.
Both of the speed testing standards use a constant drawlength, arrow weight and bow weight to test bowspeed. These are the way the two differ.
A.M.O.
Under this standard the bow being tested will have a maximum pull weight of 60lbs. The arrow will have a grain weight of 540(9 grains of arrow weight per pound of bow weight). The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.
I.B.O.
Under this standard the bow being tested will have a maximum pull weight of 70lbs. The arrow will have a grain weight of 350(5 grains of arrow weight per pound of bow weight). The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.
What is important about these two speed ratings is that they are only to be used to compare bows speed tested under the same standard. They should NOT be used to tell you what you will personally shoot for speed. For example lets take an average archer……Bill Bowshooter……..Bill has a 29 inch draw length shoots his bow at 65 lbs and shoots a 455 grain aluminum arrow. In our example neither the A.M.O. or the I.B.O standards will accurately reflect the speed of Bill’s bow. Since Bill is shooting a shorter draw than both standards, shooting an arrow that weighs 7 grains of arrow weight per pound of bow weight, and is shooting 65 lb peak weight he will shoot at a speed very different to either standard.
If we try to make some generalizations about the two different ratings we could say that the I.B.O. speed rating is much faster than most archers could achieve, and conversely the A.M.O. speed rating reflects a speed that is less than what most shooters could achieve with the same bow. If a bows I.B.O. speed rating is 320fps and its A.M.O. speed rating is 245fps that would mean the average archer would shoot that bow somewhere in the middle of that range."