Puzzled on speed

[muzzyman88]

The other night while at a local shop I decided to zip a couple arrows out of my Allegiance through the chrono. I was absolutely dumb founded to see speeds of 272 and 274 out of this thing. All numbers I ran showed me in the ball park of 285 - 290 out of this setup. My buddy PAHardwoods Old Glory was getting low 290's from the same chrono, which he and I figured would be right around his speed.

My setup when shot through the chrono was:

Bowtech Allegiance
28" draw
63lbs
gold tip xt hunter 5575 at 27"
100gr point

String had hush kit, string loop and fletcher tru-peep. No brass nock.


Here is what I don't get. My BC was 305 for this bow. Thats a 350 gr arrow at 70lbs. My current arrows weigh in around 376. Thats only 26 grains over what it was tested at. I realized the original shop scale was wrong and did put a full turn in my limbs to get the poundage up. But I really don't see that making that big of a difference.

Where did I lose so much speed at?

[buckeye]

OK.

63 pounds you lost approx. 14fps.
26 grains you lose around 8-9fps.

So right there is 22-23fps.

305-23=282fps

Add your peep in -2fps= 280fps

I would check with another chronograph to know for sure, it does look a little on the slow side for the specs.

[lghtnquik]

275 isn't bad for 28" draw length. What is your buddies draw length thats most likely where he got the speed on you?

[BowTech_Shooter]

Unless I missed something, at 63 lbs. your 376 grain arrows are 61 grains over 5 grains per pound, not 26 grains. This is why there's more speed loss than you're figuring, plus the fact you've got a 70 lb. bow backed out to 63 lbs. making it less efficient.

Try a 315 grain arrow and see what you get.

[Blodg]

ORIGINAL: BowTech_Shooter

Try a 315 grain arrow and see what you get.

I did the testing of my Allegiance at exactly 315 grains and 63 lbs. My bow is a 27 1/2" model but the measured DL was at 27 3/4" and I have a tru-peep, loop, but no cable or string silencers. I got 296.4, 295.7, 295.4, 295.3, 295.3, 295.8, 295.1, 295.1 for an average of 295 fps.

At the same 63 lbs. I shot a 350 grain arrow at 281 which gives 1 fps for each 2.5 grains of arrow weight.

Going to 70 lbs., 350 grains equals 297 fps which gives 1 fps for each 2.3 lbs. of draw weight. By-the-way, my BC said 299 and I measured 297 with a peep and loop but no silencers, pretty darn close.

Using my numbers I would estimate muzzy's speed at 275.5 fps with his 376 grain arrow. Buckeye's general guidelines for speed above were very close, I was just confirming with actual measured numbers.

muzzy, my numbers put your measured speed of 274 really close to where you should be. If the 272 is more consistent then I would guess you are either not at quite 63 lbs. or the chrono is not calibrated. It sounds like you are not sure about the scale becuase you said you knew it was off and you gave the limbs a turn, a full turn of the limb bolts gives a full 4 pounds of DW adjustment! I would find an accurate scale to start. I know mine is accurate because I calibrated it with a known weight.

Pat, my testing indicates the Allegiance is still very efficient when backing out the limb bolts! Staying at 5.0 grains per lb. I only lose 2 fps going from 70 lbs. to 63 lbs. This is much less than other bows I have tested and is another impressive thing about the binary cams!

[Sniper151]

muzzy Take the time to fine tune your setup. If center shot or nock point are off just the least little bit, you arrow will not come off the string at it's optimum trajectory. Have an experienced bow tech check it out. You will be very surprised on how much speed and how tight your groups become with just a little tweaking.

[Techy]

I agree with blodge and BBhunter...

You are right about where you should be. Get a lighter arrow or turn the poundage back
up.



Here is another comparison for you though if you wish:
I have a pretty close Example for you. I currently have an Extreme VFT (alliegance on the way) @ 63#'s and 29". Cat wiskers, No brass nock, just string loop and tru-peep, just like you. I shoot a 380 grain arrow. Our setups are about the same except for 1 " of draw.

Keep in mind that the Extreme IBO's at about 333 (top end) and the alliegance, with a bare string, about 334 or so( top end).


That puts us about equal with the exception of my 1" longer draw and I am shooting 280fps. If you knock off 8-10 fps for my inch longer draw it puts the numbers at 270-272 fps.

That puts you right on par

[BowTech_Shooter]

Pat, my testing indicates the Allegiance is still very efficient when backing out the limb bolts! Staying at 5.0 grains per lb. I only lose 2 fps going from 70 lbs. to 63 lbs. This is much less than other bows I have tested and is another impressive thing about the binary cams!

I agree this cam system is the most efficient that I've tested too however I just thought I should point out that any bow turned down from it's peak weight, regardless of manufacture will lose some efficiency due to cam orientation, the limbs losing some of their prestress (stored energy) and they'll gain brace height as well, though it's not much it all adds up.

[muzzyman88]

Ok, I feel better now. I was expecting a little more than that initially. Its shooting extremely well and that is what is most important to me. Very quiet also. I would like to gain a little speed so I will experiment with some differences in arrow components in the future.
That was my main deciding point when switching to this bow, more speed at the same poundages.

As for the scales, I've checked 3 different ones now and two registered 63 and the other was 66. I'm going with the 63lb measurement.

Thanks everyone for helping out with this. Nice to be part of the Bowtech Brotherhood.

[silentassassin]

Muzzy,

How is the bow comparing to your old bows in the speed department? When set up at the same weight with similar accessories and a similar arrow is it faster, slower, or about the same?