Agreed, it might not always be betterbut a heavier arrow shot from the same bow for all practical arrow weights always means more kinetic energy and momentum. That's just a fact and not opinion. Anyone who claims otherwise is simply incorrect.Don't take my word for it, look it up for yourself. Here's a start http://homepage.ntlworld.com/joetapley/ Go to the section on virtual mass. There are other sights as well or just get a book on archery physics.

Well, I did the math and a 400 gr arrow at 290 is 74.71 pounds of KE. A 550 gr arrow flying at 220 is 59.12 pounds of KE. That's not opinion, it's fact.

290x290x400/450,240= 74.71
220x220x550/450,240= 59.12

Now, I am no mathmetician, hell, I may have not even spelled that right, but that's a heavier arrow flying slower and producing LESS kinetic energy.

You are absolutely correct with these numbers. However unless you change something else in addition to the increase in arrow weight a bow that shoots a 400 gr arrow at 290 ft/sec will not shoot a 500 gr arrow at 220 ft/sec but rather 255.8 ft/sec using 125 grains virtual mass . That is a KE of 79.9 ft lbs.I don't know where you got the 220 ft/sec but it is incorrect.

Well, to be honest, I just made the number up, but I promise you my bow will not shoot a 550 gr arrow 255 fps. It seemed like a fair number to use.This virtual mass you bring up....I have no idea what that is.
Don't misunderstand me....I don't intend for this to sound like I am saying you are wrong, I am just trying to understand.

You may well be right about the 255 fpsbut thenof course that would indicate that it wouldn't shoot a400 grain arrow at 290 ft/sec. With regard to virtual mass, try the web site I listed. It gives a pretty good explination. The entire site is interesting too. I think of virtual mass as the equivalent amount of mass the bow has to accelerate in addition to the mass ofthe arrow. For example, if you add a silencer or a peep you increase virtual mass but again the web site or a book on archery physics will explain it better than I can.

Well, I looked over some of it....and it's way over my head. But one thing I just don't understand......how can you have the mass of an arrow and then REMAINING mass....virtual mass. My logical and not mathematical brain tells me that's a made up number. Remaining mass of what?
And my 400 gr arrow is flying 290. Although I haven't chrono'd a 550 gr arrow. Thanks for the explanation. This is actually kinda fun for me.

I think what makes this concept a bit confusing is that some of the mass in virtual mass is not mass at all but rather frictional losses or dynamic hysterisis. That's why its called "virtual" mass. It's not all real mass. I'm sure that makes no sense at all does it? But it really all comes down to this equation...

v= (2SE/(m1 + m2))^1/2

where:
SE = Stored energy or Total energy in the system
m1 = arrow mass
m2 = virtual mass
v = velocity

It might not be obvious butm2 is in the denominator so if you increasem2 then you increase how much you divide by and therefore v goes down. If you lower m2 v goes up.

As m1 is only part of the mass that is accelerated, m2 is the "remaining" amount.

Virtual mass is not a "made up" number and it can be measured for your bow if you have a chronograph and and arrow weight scale.

I've probably made it more confusing...

Gentlemen,

This is n argument that can be settled by no one here with out the quatitative fomulas. All it is is physycs.

Shooting a heavier arrow will NOT neccessarily produce more KE or PE (what some of you refere to as "momentum".)

In theory, yes, a hevier arrow will broduce more PE and KE. However, the arrow will fly slower and have a different trajectory UNLESS the draw weight of the bow is incresed to off set the weight of the arrow.

I have done the math too and a heavier arrow will produce more KE at closer range and less KE than a lighter arrow at longer range. Gravity robs the heavier arrow of KE earlier than the lighter arrow.

I think you might be pleasantly surprised then. I've done this many times where we have chronographed with 1 arrow weight and then used the equations to predicta new velocity with a different arrow weight and it's always within 2 ft/sec of the new chrohographed speed.

I respectfully submit that you have done the math incorrectly. Going to a heavier arrow will increase the amount of initial KE and the advantage you gained over the lighter arrow increases the farther down range you go. All flight characteristics being equal, heavier arrows maintainke and momentumbetter then lighter arrows. Go to the web site I listed and then go to vortex shedding.

I gave you the formulas and a web site that will confirm they are the correct formulas. You can also find them in a physics book. And btw there are a lot of people here that are more than capable of solving the equations and understanding the physics.

Absolutely correct, and that's the tradoff. Going to a heavier arrow will give you more PE & KE but also a bigger arch in the trajectory. Whether or not it's worth it is open to opinion. Whether or not it's true isn't.