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**SAVIOUR68** · 01-22-2014, 06:03 PM

I believe those posted numbers are slightly distorted Rick. 125 grs extra arrow weight does not translate to 50fps less in arrow speed. His prior post showed 5oogr arrow at 160fps =.3552 momentum, he stated that 620 gr arrow was 150fps =.412 momentum slugs. even at 560gr arrow at 150fps = .373 momentuam. The numbers increase with added weight. Bow efficiency dictates FPS in ALL cases.

**Mike Javi Cooper** · 01-22-2014, 06:29 PM

Personally I think you're about at optimum with the 620 grain arrow.. you might go to 650 or down to 600 but you're in the ball park.

Testing my Blackhills II's one 58" / 49lbs @28" and 60" /49lbs @ 28" I found the sweet spot to be between 640 and 660 after that I started seeing a loss on my weight to speed ratio.

**RickBarbee** · 01-22-2014, 06:37 PM

That's the reason I said - "All just in theory of course, because we don't know for sure what your speeds would be"

The difference in his 500gr arrow, and 620gr arrows as per your post is 13 fps slower.
That is roughly 0.1083fps loss of speed per every additional gr of arrow. That would be .54 fps for every 5 gr.

I'll refigure it using that deferential as the rule of thumb speed difference, and see what we get.

Rick

**RickBarbee** · 01-22-2014, 07:11 PM

Here are the numbers using a .1083 speed difference per gr of arrow.

```````````````````````````````````
@ 700gr / 14gpp / 141.4fps

Momentum = .439130

Kinetic Energy = 31.04652

```````````````````````````````````
@ 625gr / 12.5gpp / 149.5fps

Momentum = .414540

Kinetic Energy = 30.98692

```````````````````````````````````
@ 600gr / 12gpp / 152.1fps

Momentum = .404614

Kinetic Energy = 30.75066

```````````````````````````````````

@ 550gr / 11gpp / 157.6fps

Momentum = .384560

Kinetic Energy = 30.30338

```````````````````````````````````
your current setup

@ 500gr / 10gpp / 163fps

Momentum = .361579

Kinetic Energy = 29.46872

```````````````````````````````````
@475gr / 9.5gpp / 165.7fps

Momentum = .349190

Kinetic Energy = 28.93041

```````````````````````````````````
@450gr / 9gpp / 168.4fps

Momentum = .336202

Kinetic Energy = 28.30823

```````````````````````````````````
@425gr / 8.5gpp / 171.1fps

Momentum = .322615

Kinetic Energy = 27.59974

```````````````````````````````````
@400gr / 8gpp / 173.8fps

Momentum = .306654

Kinetic Energy = 26.49497

```````````````````````````````````
@375gr / 7.5gpp / 176.5fps

Momentum = .293644

Kinetic Energy = 25.91413

```````````````````````````````````
Obviously, by that deferential the heaviest arrow has the most momentum, but I don't believe the bow is efficient enough to only lose 21.6fps with an additional 200gr of arrow.

Like I said, we won't know for sure without actual chrony readings with different arrow weights, and I bet when those are revealed he'll still come being real close to the best all around he can get with his current setup, which was the point I was trying to make from the get go.

Rick

**trad"Doc"53** · 01-22-2014, 07:16 PM

I shouldn't have read this, dang I got a headache!!!

**RickBarbee** · 01-22-2014, 07:29 PM

Originally posted by trad"Doc"53 View Post

I shouldn't have read this, dang I got a headache!!!

LOL, I love playing with this kind of stuff.

Rick

**M.E.B.** · 01-23-2014, 06:26 AM

Originally posted by trad"Doc"53 View Post

I shouldn't have read this, dang I got a headache!!!

Me too.

Yep someplace there has to be a medium between too fast and light and too heavy and slow.

Rick, so hopefully I will get a chance to play with my bow this weekend. Work has informed me I will be putting my last deer hunt off by a few days so I will have more time.

Using your numbers what I may do is to switch from shooting 200 grain Muzzy Phathoms to 125 Magnus or Zwickey with 125 steel inserts and shoot a 60 grain heavier arrow at 560 grains. This way I will not loose as much speed, still increase arrow weight and will not have to play with arrow tubes.

Will see how it goes and keep you guys informed.

Thanks for doing the math. I will shoot a variety of weights and post a chart.

I think when I have my little feed at Vanderpool I will set up my chrono and have people do a little bow poll there in person. I don't see how some people shooting close to my set up are getting that much more speed than me. We'll do a little scientific research and see how things shake out.

Thanks again.

**SAVIOUR68** · 01-23-2014, 06:54 AM

Hey Rick I was not trying to give ya beat down on the numbers :]
I believe you are correct about diminishing returns once a arrow gets too heavy.

**RickBarbee** · 01-23-2014, 07:06 AM

Originally posted by SAVIOUR68 View Post

Hey Rick I was not trying to give ya beat down on the numbers :]
I believe you are correct about diminishing returns once a arrow gets too heavy.

LOL I know that Bro.

All you did was give me another angle to approach it from, and I love multiple angles of approach.

Rick

**Bisch** · 01-23-2014, 08:30 AM

Originally posted by M.E.B. View Post

I think when I have my little feed at Vanderpool I will set up my chrono and have people do a little bow poll there in person. I don't see how some people shooting close to my set up are getting that much more speed than me. We'll do a little scientific research and see how things shake out.

Thanks again.

I do not know how you would "calibrate" a chrono, but I do know it is possible for them to be off. Just a thought?

There also quite a big spread between different bows, but I doubt that is a big part of this cause you shoot reputable high-end bows.

Bisch

**M.E.B.** · 01-23-2014, 08:55 AM

Originally posted by Bisch View Post

I do not know how you would "calibrate" a chrono, but I do know it is possible for them to be off. Just a thought?

There also quite a big spread between different bows, but I doubt that is a big part of this cause you shoot reputable high-end bows.

Bisch

My chrono and West Houston Archery chrono are only off by 4 fps with my compound. Theirs 260 fps and mine 264 fps. I figure a compound would have less margin for error as you can only pull it so far back.

That spread between different bows is why I want to to a little test at Vanderpool. One shot through the chrono should be worth a chicken dinner.

**RickBarbee** · 01-23-2014, 08:56 AM

Originally posted by Bisch View Post

I do not know how you would "calibrate" a chrono, but I do know it is possible for them to be off. Just a thought?

There also quite a big spread between different bows, but I doubt that is a big part of this cause you shoot reputable high-end bows.

Bisch

Jerry, shooting through the chrony is pretty much an absolute must to figure out the speed differences, and the efficiency of the bow with different arrow weights, but the accuracy of the chrony will not effect the incremental outcome.

If inaccurate it might not show the exact numbers for each arrow, but it will still show the incremental increases/decreases, and show which one has the best delivered energy.

Just want to shoot them all through the "same" chrony.

Rick

**RickBarbee** · 01-23-2014, 09:01 AM

Originally posted by M.E.B. View Post

I want to to a little test at Vanderpool. One shot through the chrono should be worth a chicken dinner.

Mike, if you're going to do that, you need to have a bow scale, and a grain scale in the station also. Weigh the bows, and the arrows to go along with their speed results.

That's the only way your going to get an accurate comparison.

Rick

**M.E.B.** · 01-23-2014, 09:13 AM

Originally posted by RickBarbee View Post

Mike, if you're going to do that, you need to have a bow scale, and a grain scale in the station also. Weigh the bows, and the arrows to go along with their speed results.

That's the only way your going to get an accurate comparison.

Rick

Yep thought of that too. Have all of the above.

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